There are 3 stages in the development of the kidney:

• Pronephros (A)
• Mesonephros(B)
• Metanephros(C)

Development of the Vertebrate Kidney. Source: Developmental Biology 8th edition, Fig.14.21(Part1)

1.  Pronephros

• This is the first kidney
• It develops during the 4^th week of uterine life in the cervical region of the intermediate mesoderm.
• The pronephros contains lots of segmental vesicles and has the pronephric duct that grows caudally toward the cloaca.
• The pronephric duct is in the embryo and thus cannot filter materials outside the embryo. Therefore it is said that the pronephro kidney is nonfunctional in humans thus it degenerates.

2.  The Mesonephros (The 2nd Kidney)

• The Mesonephros kidney follows the development pronephros in about the ending of 4^th week of uterine life. It is also comes from intermediate mesoderm and is located in the throcolumbar area where the pronephric duct that was developed in the pronephos stage continue to elongated caudally and become the mesonephric tubules. Most of this tububles eventually degenerates but leave behind the Mesonephric duct or Wolffian duct which extends towards the cloaca
• The  mesonephros is the functioning kidney during the 1^st trimester and it produces urine during weeks 6-10.
• It contributes to the:
• Epipdymis
• Vas deferens
• Seminiferous tubules

3.  The Metanephros- The Permanent Kidney

Primoridium of the Metanephros of a Five-Week Embryo

• This kidney begins to develop in the 5^th week of the embryonic period.
• It appears in the sacral region of the intermediate mesoderm
• During the 5^th week the Mesonephric duct fomr the mesonephros kidney develops an outgrowth called the ureteric duct. This duct is close to the attachment of the cloaca.
• The ureteric duct eventually form the:

i.     ureter
ii.   renal pelvis
iii. major calyces
iv. minor calyces
v.   collecting tubules

The ureteric bud interacts with a portion of undifferentiated intermediate mesoderm called the metanephric mesenchyme. This interaction induces differentiation and thus the formation of the:

i.    renal tubles
ii.   glomerulus
iii. distal & proximal convoluted tubules
iv. Loops of Henle

If there is an abnormal interaction between the ureteric bud and the metanephric mesenchyme, several congenital malformation of the kidney may result.

About The Author Sonya McKenzie

I am currently a "50% doctor." You might be wondering what that means. Well, I am currently in my last few weeks of my second year in medical school. I love anything to do with science and medicine. I have great interest in medicine from the preventive aspect.

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• What is a tumor?

Cancer Cell

A tumor is the most basic symptom of cancer. However, anyone can have a tumor. The nature of the tumor, however, determines whether a person has cancer or not.

Well, a tumor is basically an extra mass of cells out of place in the body. It occurs when somebody’s cells decide to divide due to some or any reasons without any functions at all and are completely useless to the body.  It’s more like some group of cells autonomously (without any objection) decides to divide for the heck of it, useful or not to our body. Now, this tumor may or may not cause a variety of problems in our body, depending upon the location and size of the tumor. It also shows uncontrolled growth and may grow to gigantic proportions.

• Types of tumors:

1. Malignant Tumor

So, tumors are basically a bunch of cells which decide to rebel against our own body and divide mercilessly and make it a point to convince other cells of the body to divide too. These cells become unproductive and procrastinate on essential bodily functions, as some of them have not yet decided what function to choose as their own.

For example – A pancreatic cell gets fed up and decides to divide but upon division does not exhibit any properties of pancreatic cell. So, it is just any ordinary cell, with no apparent function at all. Just a cell with a nucleus, mitochondria, vacuoles, Golgi bodies and protoplasm. Now such a group of daughter cells, which refuse to do anything for the body but survive is known as a malignant tumor.

So as per medical definitions, a malignant tumor is just a mass of undifferentiated ( since it is undifferentiated, it cannot perform any essential function of the body) cancerous cells.

• Why called cancerous?

These cells are called cancerous because these malignant tumors show one of the main features of cancer- Metastasis (meta-stas-is).

Metastasis is the official term for what can be said as spread of cancer. It is essentially that one of the cells of the tumor goes to some other part of body and convinces the cells of that part of the body to divide again, thus triggering a tumor in that part of the body and as a result, spreading cancer all over the body. Thus, the spread of cancer is metastasis. And since these malignant tumors cause metastasis, they are also known as cancerous tumors.

How Metastasis Occurs

2. Benign Tumor

Benign tumor is simply a mass of cells on strike. They are well-differentiated and though they divide just the same, these tumors are enclosed in a fibrous capsule. They mean no harm. However if they are located in some specific location like the brain, their mere presence can hamper the functioning of the body.

Since these tumors are enclosed in a fibrous capsule- they do not spread this condition throughout the body and are relatively harmless. It is not necessary for us to remove them unless they possess some threat to our body. So the only exception when a benign tumor causes cancer is brain cancer since its mere presence affects the functioning of the body.

• Tumor and Nutrition

Tumor after all, is but a bunch of rebellious cells. They too need nutrition and oxygen to survive. Our body knows not to differentiate between normal cells and cancerous cells and provides blood to both of them just the same.

So a majority of tumors are situated near blood vessels. Without vessels tumors cannot grow to be larger than a small fraction of an inch.

• What if a tumor formation has started away from a blood vessel? Will it survive?

A dead tumor is usually just eaten by macrophages, the eat-all-the-dead cells of the body. To survive, however, these cells have a trick. When the area around the cells in a tumor starts to get too far from a blood vessel, the oxygen and nutrient levels start to go down. A decrease in oxygen is also called hypoxia.

Hypoxia triggers changes in the behavior of the tumor cells. The tumor cells produce (or cause nearby cells to produce) growth factors that stimulate the formation of blood vessels.  Tumors that do not produce (or cause other cells to produce) angiogenesis (formation of blood vessels) factors cannot grow.

Angiogenesis factors produced by tumor cells or nearby cells can cause the development of blood vessels that feed the growing tumor.  Because this is a normal signal for the cells forming the blood vessels, they are really just doing their job.  The tumor ‘tricks’ the body into creating new blood vessels.  The blood vessels created in this way are not exactly the same as normal blood vessels.  Frequently they are less organized and leakier than normal vessels.

Freaky link: World’s biggest tumors ever seen

About The Author Srushti Kumbhare

Hey everyone! I'm Srushti. I'm a science student. I love biology, knowing how things work inside things, that every system has various systems in it. Biology is full of wonder and it is one of my favorite hobbies. I really hope the articles are helpful. If you have any questions, I'll be happy to help. :)

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Proprioception

Proprioception is the ability to know where your limbs, or parts of your body are in space without looking at them.

Even if you closed your eyes, and were deprived of all of your “external senses” (vision, olfaction, hearing, touch and taste), you would still be able to “know” where your right foot is, or how to touch your left knee with your right hand. Pretty cool!

Stretch Receptors

Let’s look at the mechanics behind proprioception.
When you move your arm, for example, “who” does the “moving?”

Muscles move your arm by contracting or stretching and thus by changing the angle formed by two connected bones.
It makes sense then (no pun intended), that sensory receptors for proprioception would be found hidden inside muscles and tendons.
Muscles generally undergo only two types of movement: Stretch or Contraction.

• Any of these could have been used to monitor the state of our muscles, but it so happens that, for proprioception, our bodies listen only to how much “stretch” is being performed.

Muscle Spindles

Muscle Spindle. Credits: drkhan1 (flickr)

Muscle spindles are one type of stretch receptors.

They are big enough to be seen by the naked eye (fun!) and they tend to measure between 2 to 4 millimeters.
You can find them in the “belly” of the muscle (yes, that’s the round part of the muscle) hidden within the extrafusal muscle fibers – and therefore parallel to the extrafusal muscle fibers!

The reason this muscle spindles can detect stretch is because they have ion-channels that open when they are stretched. When these ion-channels open, ions flow and result in the creation of a small current that is then transmitted to the brain by the nervous system.

This electric pulse is the information telling the brain that this muscle spindle is being stretched.

Golgi Tendon Organ

Golgi Tendon Organ. Credits: drkhan1 (flickr)

Golgi tendon organs work in a way that is very similar to that of the muscle spindles. As you might have guessed from the name, they are located inside the tendons (the part of the muscle tissue that is attached to the bone) and they respond to stretch.

• Contrary to the muscle spindles, however, they are arranged in series (whereas the muscle spindles are arranged in parallel).

As the Golgi tendon organ is stretched, it opens cation channels that results in an electric pulse.

It might seem surprising at first that the body decided to monitor stretch instead of contractions, but it actually makes sense. If you think about it, stretching a muscle too far can result in very serious damage: you could tear the muscle fibers or even break the joint.

Minimum To Remember

If you want more articles and videos about the Nervous System, you can find them here. More resources are available to help make Biology fun. I invite you to absorb all the content you can find here at Interactive-Biology.com.

About The Author Mag Reves

Hi, I love to talk about, neuroanatomy, psychology, memory,... and pretty much anything related to the brain. I graduated from UCLA with a degree in Neuroscience and I also run another website dedicated to helping Pre-Meds become great medical school applicants.

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In unidirectional ventilation, the medium (air or water) moves across tissues in one direction. This method is efficient because the medium is always fresh. Fish and birds have unidirectional respiration.

The second type is bidirectional respiration, which implies that the medium enters and exits through the same channel. In this case, the medium (air) contains more waste and is not as efficient.

Cutaneous respiration is also possible and occurs via the skin. Cutaneous respiration is unique in that it can occur in air or water. Amphibians utilize this form. Each type of respiration requires modified organs and methods of obtaining oxygen.

Unidirectional Respiration: Fish

Fish have two important organs for respiration: gills and gas bladders.

Gas bladders have two possible functions. They can help the fish stay buoyant, in which case they are called swim bladders, or aid in respiration (lungs).

The function of the gills is to draw water into the lungs, and fish have two methods of using their lungs: bucal pump (opercular) and ram (passive) ventilation.

In opercular ventilation, the fish takes in water through the mouth (bucal chamber) and it exits through the gills (opercular chamber). Pressure in the mouth is kept higher than pressure at the gills to ensure a supply of fresh water and oxygen. Unidirectional flow is advantageous because it allows for greater oxygen concentration in the bloodstream.

Bidirectional Respiration: Mammals and Reptiles

This type of respiration is not as foreign to us because this is the type of respiration humans have. Bidirectional is not as efficient as unidirectional because there is extra waste and the oxygen concentration is much lower. The amount of waste is greater because air that is inhaled and air that is exhaled travel through the same channel.

Alligators

Mammals and reptiles have very similar respiratory systems, but there are a few key differences. Reptiles have alveoli and bronchioles, but they are fewer in number. The lungs of reptiles also have less surface area as they are ectothermic and do not require as much oxygen for metabolism.

Respiration is slightly variable among the reptiles, but the overall method is like that found in mammals.

Cutaneous Respiration: Amphibians

Amphibians have two forms of respiration: bidirectional and cutaneous.

Cutaneous respiration allows organisms to breathe through their skin. As a result, they must live near the water and have moist skin. This type of respiration requires moist skin and diffusion of oxygen takes much longer than in lungs. The epidermis (top layer of skin) is much thinner than the layers beneath it. The deeper layers of skin are also vascularized so the oxygen can get into the bloodstream.

Frog

Cutaneous respiration allows amphibians to live in water and on land, and it also makes the amphibians an unique group of organisms.

Summary:

Among the vertebrates, there is a great deal of variety in the types of respiration and the modifications involved. In summary, fish and birds have unidirectional flow, mammals and reptiles have bidirectional while amphibians have bidirectional as well as cutaneous respiration.

The important organs for fish include the gills and swim bladder, while the lungs are important for mammals, reptiles and amphibians. It is also important to remember that amphibians are special because they can use their skin for respiration.

About The Author Kristen Williford

Hi everyone,my name is Kristen. I am a pre-med student studying Biology and Spanish. I'm also a beauty blogger, active volunteer, coffee lover and avid reader. I hope you enjoy my articles and find them informative.

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During my first year at UCLA, my psychology professor handed us a gift. He had himself received that gift from his psychology professor when he was in college.

While in college my professor was a varsity basketball player. He was very good and trained hard every day. However, by the end of his second year he realized that basketball was fun, he was good at it, but it wouldn’t carry him to the place he wanted to get to. He realized that to get a sense of fulfillment he needed to become a great academic. He wanted to become the best researcher.

So, he decided to switch careers. He’d stop playing basketball and start his academic career.

But,…

… He had to learn how to study!

A little lost he asked his psychology professor what the best study method was. And that’s the gift he received, the gift he handed us down, and that’s what I am giving you now.

It’s called the 3 x 3 x 3 method.

It’s very simple.

Yet, it’s very effective.

How effective?

My professor went on to triple major (Biology, Chemistry, and Psychology) in 2 years with a 4.0 GPA.

He studied like crazy, but the method worked like magic.

The 3 x 3 x 3 Method

Review 3 min after class. Time required: 15 min ~ 20 min

You might have already heard about this, but you might not know why it works.

In other words, if you don’t review right away, you’ve basically just wasted one hour of your time…

It’s also your chance to make sure you understand all the concepts while they are fresh in your mind, and go to office hours to get some clarifications if you need them. Saves time for later.

Review 3 hours after class. Time required: 45 min ~ 90 min, depending on your class and your homework load.

3 hours after class basically means to review when you get home at night. You will review as to understand the concepts and memorize the material you covered in class today. Take the time to jot down a few graphs or drawings if they help you really tie the full concept of the lesson together. Create a story around the material that helps you remember it.

This is also the time when you do your homework, or catch up on textbook reading.

Why do you have to do this 3 hours later, on the same day?

But by exposing the material to your brain at night too, it tells it that this must be quite important and that he needs to pay attention and hold it in memory a little longer.

Review 3 days after class. Time required 15 min ~ 25 min.

By this stage, your brain will do what it can to keep the material in memory… just in case. But by the 3rd day, if it appears that you don’t need the material,… it will start discarding it again.

So what do you do? You test yourself on the material you studied 3 days ago. Go over your notes once, and then self-quiz yourself on the important concepts or nomenclature form that class. If you had homework, go over the questions you found difficult.

You will have a much easier and fluid time reviewing for a midterm or for a final. You will be able to sleep well that night, and be fully focused during the test.

A good part of the material you learned will stay with you for a much longer time though. You won’t forget everything 5 min after the test is over.

Who will benefit from this study method?

Long term retention and understanding of the material is especially useful if:

Now, this method is a lot of work! To be honest, I only used it in classes I really cared about, or that where especially challenging-memory wise. For all the other classes, I used the second best study method: Cramming!

More resources are available to help make Biology fun. I invite you to absorb all the content you can find here at Interactive-Biology.com.

About The Author Mag Reves

Hi, I love to talk about, neuroanatomy, psychology, memory,... and pretty much anything related to the brain. I graduated from UCLA with a degree in Neuroscience and I also run another website dedicated to helping Pre-Meds become great medical school applicants.

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Psoriasis, for example, is a result of an overactive immune system that manifest through the skin. The skin, besides protecting us, gives us insight on the performance of key organs.

Check out Srushti’s article “What is Psoriasis” for an explanation of causes and symptoms.

The liver and colon are two main contributors to maintaining health. Your liver keeps your blood clean and clear while your colon eliminates toxins and byproducts out of your system. Do not get me wrong, the heart and other major organs are a vital component as well.

The condition of your skin is closely related to what is happening inside your body.  The body is resilient. It may take months or years before you see a visible change is seen on lab results or imaging.  The body talks in a variety of ways, it’s time we listen.

In this series, we are going to discuss three possible triggers or aggravates psoriasis, from a Naturopathic perspective. Let’s start with Stress.

Stress

Stressed Woman

Stress has a big impact on the body. What we think, feel, and how we react to those thoughts, feelings, and situations are key to our health. Remember, small bursts of stress are normal. Our body has its normal “fiight or flight” response. Chronic stress is damaging to our body. It can suppress the immune system, distract your focus, and have a direct effect on your health.

• Physical: trauma, physical ailment (High blood pressure, diabetes, etc.)
• Mental : Anxiety, Depression, Type A personality
• Emotional stress : loss of loved one, excitement, worrying about your cat or dog, a big exam or project due soon

Caveat for emotional stress: The experience of emotion is a gift. We are hard wired to feel and react to situations yet the key is the duration of those emotions and understanding how our perspective influences the outcome psychically and mentally.

The body reacts, in the same manner, to all categories of stress.  It produces cortisol, a hormone, that prepares body to “fight or flight” by increasing glucose levels, breaking down fats, carbohydrates and protein, shunting blood away from organs to periphery all in the name of energy.  Yet we do not run or fight, we sit down at our desk or couch… how ironic.

Next time you feel stressed:  acknowledge it, take a deep breath, take a walk (i.e. exercise) and do not freak out! Your body and skin will thank you for it.

In my next article, we will discuss Psoriasis and Food.

Leave a comment below sharing your thoughts!

About The Author Stacy Mobley

Hello, I'm Stacy, a 4th year Naturopathic Medical student, who loves sharing my knowledge and "ah ha" moments! I'm very passionate about empowering others to truly understand how amazing their body is, how to cherish and protect it ;-) Follow me on twitter: @dairyfreenow

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Causes of Cancer

Cancer, unlike many of the life-threatening diseases, is caused by a variety of environmental factors and not virus or germs. However, there are some exceptions.

HPV Human Papilloma Virus

Human papilloma virus, for example, causes cancer of the cervix in females. Such cancer causing factors are known as carcinogens. When cancer is diagnosed, it can be either due to one or the combination of a variety of factors.

These factors are:

• Chemical Carcinogens

Prolonged exposure to a number of chemicals like coal-tar, soot, asbestos, nickel, lead, chromium. etc causes lung cancer. Vinyl chloride and aflatoxin B may cause cancer of liver. Aniline causes cancer of the urinary bladder and arsenic causes skin cancer.

• Radiation

Unmonitored radiation from various radioactive sources usually do more harm than good. They cause gene mutations and even cancer. Continuous exposure to x-rays, alpha rays, gamma rays and radiation from radioactive isotopes must be avoided.

• Biological Agents

Though rare, even viruses can cause cancer. For example hepatitis B virus and hepatitis C virus may cause liver cancer. Parasite Schistosoma haematobium is associated with cancer of the urinary bladder.

• Dietary factors

  
  
  

  Man eating fatty food

International studies suggest that diet high in fat increases risk of cancer. What happens is, when we ingest a large amount of fatty foods, excessive bile acids are produced that aren’t thoroughly consumed. These bile acids and their metabolites produced by intestinal bacteria are carcinogenic in nature.

• Genetic Factors

A person whose family has a history of cancer is more likely to develop cancer.

• Cancer due to Habits and Customs

  

  Alcohol and Cigarette

  Excessive alcohol consumption may cause cancers of liver and esophagus. Oral cancer are more prevalent in people who have cigarettes, cigars or chew tobacco.

About The Author Srushti Kumbhare

Hey everyone! I'm Srushti. I'm a science student. I love biology, knowing how things work inside things, that every system has various systems in it. Biology is full of wonder and it is one of my favorite hobbies. I really hope the articles are helpful. If you have any questions, I'll be happy to help. :)

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Gas molecules dissolve into the water that covers the alveoli and diffuses along a concentration gradient across the respiratory membrane and capillary wall into the blood. This is due to the partial pressure of oxygen in atmospheric air.

Gas Exchange at the Respiratory Membrane

You may have encountered the concept of partial pressures in chemistry. Basically, in a mix of gases, each pure gas represents a part of the total pressure. Let us consider air — a mixture of oxygen (21%), carbon dioxide (0.03%), and nitrogen (78%) as well as a few other trace gases.

The atmospheric pressure of air is 760mmHg, since 21% of air is oxygen, 21% of 760mmHg is 159mmHg and thus, the partial pressure of oxygen in air is 159mmHg.

Partial Pressures of Oxygen and Carbon Dioxide

If you look at the table (image courtesy of the author for use on the Interactive Biology website) above, the partial pressure of air (PO₂) of alveolar gas is 100mmHg as inspired air mixes with staler expired air. You may have noticed that the arterial blood has a PO₂ of 95mmHg. This is because the respiratory system involves two blood supplies; the pulmonary circulation and bronchial arteries. The pulmonary circulation carries blood from the heart, through the lungs to be oxygenated and then back to the heart to be pumped around the rest of the body.

The bronchial arteries are branches of the thoracic aorta and they supply the lung tissues with oxygenated blood however, there are no veins to return de-oxygenated blood to the heart, instead the deoxygenated blood simply mixes with the pulmonary system, hence why systemic arterial blood has slightly less oxygen.

So what happens to oxygen when it passes through the alveolar membrane? Some of it dissolves into the water in the plasma; however, most of it enters red blood cells to bind with haemoglobin, each of which have four binding sites.

Haemoglobin Molecule - Image courtesy of user Benjah-bmm27 at commons.wikimedia.org

A vital concept in respiratory physiology is the oxygen-haemoglobin dissociation curve.

Oxygen-Haemoglobin Dissociation Curve - Image courtesy of user Diberri at commons.wikimedia.org

The shape of the curve shows us that the PO2 needed to load the first oxygen molecule onto haemoglobin is higher than that needed for the second to fourth molecules. This is because the binding of the first molecule alters the shape of the haemoglobin and facilitates the loading of the other three molecules. Once 95% of haemoglobin has been filled, it starts to get harder for oxygen to find empty binding sites to load.

The blood oxygen saturation of a regular, healthy person is 98% or higher. Saturations of <95% are considered abnormal and should be treated as with even a small decrease in PO2 can cause a rapid drop in blood oxygen saturation.

In my next article I will be talking about the factors that change this curve as well as CO2 exchange at the tissues.

About The Author Christine Wickham

I am a second year medical student studying at Monash University in Australia. I am passionate about medicine and I love to share my knowledge with others!

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Antigen-Antibody Complex

The most important and common process in our immune system is the formation of antigen-antibody complexes. But first…

What is an Antibody?

Antibody is a protein found in our body, also known as Immunoglobins (Ig). They are serum proteins, meaning they are usually found in blood and belong to a clan of proteins called gamma globulins.

This protein is produced in response to antigens. In short, they are the poison produced by the army of our body to encounter foreign substances which invade the body.

What is an Antigen?

Antigens are substances produced by foreign bodies. They may be proteins, carbohydrates, nucleic acids or lipids. They trigger the formation of antibodies. Thus, any foreign substance which can stimulate the immune system of our body is an antigen.

Sometimes, these foreign bodies themselves stimulate our immune system. Hence, these foreign bodies by themselves can also be known as antigens. Thus, antigens may also be pollen, pathogens and spores.

In short, antigens are the harmful germs, pathogens or a product of a germ or pathogen or other foreign substances which act like threats and may disrupt the normal functioning of our body. In order to stop this disruption, our body produces antibody to protect itself and destroy the antigens, as well as antigen producing germs that may have gained access to our body.

Structure of an Antibody

Parts of an Antibody

Antibodies are Y-shaped proteins with four polypeptide chains. The two polypeptide chains are long and identical whereas the other two are also identical but short.

The long chains are known as Heavy chains or H chains and the short chains are known as Light chains or L-chains.

Both the chains are held together by disulphide bonds like magnets. Both chains have a distinct region and a variable region. This variable region is the one where all the action occurs. It acts like a lock and key mechanism, and is used to combine with antigens in a death wrap. This action site is also known as paratopes.

Types of antibodies

There are five types of antibodies:

1. IgA – This immunoglobin protects the body against gastro-intestinal and respiratory problems. It is commonly found in milk and saliva.
2. IgD- This antibody activates the B cell after interacting with any antigen similar to an informant.
3. IgE – This antibody controls allergic reactions.
4. IgG- These are extremely important antibodies which stimulate phagocytes. They are the ones that a mother passes on internally to a child for immunity.
5. IgM – This is the largest antibody. It also helps in the activation of B-cells.

Antigen-Antibody reaction

An antigen and antibody reaction works like a lock and key mechanism. The study of such reactions is known as serology. In this reaction, the epitopes of antigen reacts with paratopes of antibody forming antigen-antibody complex. Though it is extremely specific, it goes through either of the following steps:

• Agglutination:  Here, antibodies clump the antigens together which are later destroyed by phagocytes. Thus by clumping them together, phagocytes can detect them more easily.
• Precipitation: Here, soluble antigens are precipated and destroyed by the phagocytes.
• Opsonization: In this method, antibodies are coated on microbial surface after which antigen locks in. This makes it more susceptible to phagocytosis.
• Neutralization: Here, antibodies blocks or neutralizes the harmful chemicals produced by antigens. These are later destroyed again by phagocytosis.
• Complement Activation: Once the lock and key mechanism perfectly fits into the place, it leads to cell lysis.

Thus, we see that antigen-antibody complex acts as bait for the phagocytes, ultimately leading to their demise.

About The Author Srushti Kumbhare

Hey everyone! I'm Srushti. I'm a science student. I love biology, knowing how things work inside things, that every system has various systems in it. Biology is full of wonder and it is one of my favorite hobbies. I really hope the articles are helpful. If you have any questions, I'll be happy to help. :)

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Vision

The whole neural network making vision possible is absolutely remarkable but for this article we will only mention the cells that can actually perceive “light.”

Receptors involved in vision are called photoreceptors. This word is easy to remember as “photoreceptor” stands for “Receptor of Photons.” (Photons travel with light rays).

Different species have different types of photoreceptors. We humans have only two types: Rods and Cones. They are both located in the retina of our eyes.

Rods

Cones

As we have just seen, cone cells are mostly located in the fovea, are less sensitive to low light intensity (i.e: they work best in bright light), they are less numerous than rod cells and they can discriminate colors.

Actually, one rod cell cannot discriminate every color of the visible spectrum. There are 3 sub-categories for rod cells:

Cones. Image Credit: Madhero88

(Attention the nomenclature is… very uncreative!)

Trichromatic vision. Image Credit: TAKASUGI Shinji

All other colors are due to different rod types being activated at the same time by intermediate wavelengths.

Olfaction

Olfaction is a VERY important sense that is highly undervalued… until we loose it. More on that later.

I won’t say much more about the neural network that is involved in the full perception of smells, however I do want to bring your attention to the sense of smell!

You never knew the sense of smell was so important!

Minimum to Remember:

Vision

Olfaction

About The Author Mag Reves

Hi, I love to talk about, neuroanatomy, psychology, memory,... and pretty much anything related to the brain. I graduated from UCLA with a degree in Neuroscience and I also run another website dedicated to helping Pre-Meds become great medical school applicants.

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Psoriasis (p – silent) is an autoimmune disease. This disease occurs when one of the main features of the immune system – recognition between self and non-self is compromised.

Psoriasis of the hairline and of the scalp

What happens in Psoriasis?

Psoriasis is an autoimmune disease of the skin, including the scalp.

Now. we all know that we keep shedding skin periodically as an immunity measure for the body. See, our skin functions like a baked self puffing puffed pastry that reproduces on its own so that you never run out of it.So like multiple layers of pastry in puff pastry, our skin too has and at any given time, keeps producing skin cell layers that is epidermal layers.

When cells of the first layer are shed, the second layer is already beneath it and it’s as if nothing happened. Since this takes place on a microscopic level, we do not notice it.

However, in psoriasis, our brain gets confused and identifies our own skin as a potential threat to our body. Therefore, the previously discussed T cells attack our skin at various points on our body.

This causes a major inflammation and in order the heal the damage, the skin undergoes rapid (extremely rapid as if on jet mode) growth which leads to over accumulation of skin layers or extremely densely layered puff pastry. Since the upper layers haven’t been shed yet and there are already multiple layers formed, the skin  appear scaly and reddish at various places like a rash.

Having such rashes all over the body due to major confusion in our immune system is known as psoriasis.

Causes of Psoriasis

Exact causes are not known yet but they are said to genetic or the condition is triggered due to some bacterial attack like strep throat or environmental factors or even stress. People who are HIV-positive too often have psoriasis.

Symptoms of Psoriasis

Psoriasis - pitted fingernails

People afflicted with Psoriasis exhibit the following symptoms:

• Rashes
• Scaly red inflamed skin
• Flaky scalp and skin
• Pitted fingernails

Treatment of Psoriasis

Psoriasis is caused by immune system, hence drugs like methotrexate and cyclosporin are used. Sometimes, drugs like infliximab and adalimumab are used.

About The Author Srushti Kumbhare

Hey everyone! I'm Srushti. I'm a science student. I love biology, knowing how things work inside things, that every system has various systems in it. Biology is full of wonder and it is one of my favorite hobbies. I really hope the articles are helpful. If you have any questions, I'll be happy to help. :)

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Signal to Contraction

Contractions of the heart begin with something called the Frank-Starling reflex. This reflex is able to detect an excess of blood in the heart, which causes it to contract. This reflex also monitors the strength of the contraction. The contraction squeezes the excess blood out of the heart.

The signal begins in the sinoatrial node, or SA node for short. The SA node is essentially the pacemaker of the heart.

Cardiac Conduction System

The SA node is located in the right atrium of the heart and contains specialized muscle cells. These cells behave very much like nerve cells rather than cardiac cells because they do not contract and release action potentials.

From the SA node, the signal travels across the atrium, through internodal fibers and arrives at the atrioventricular node, or the AV node. The AV node is located between the atrium and ventricles.

From this point, the signal travels through the AV bundles, which you may also see referred to as the bundle of His. The AV bundle (bundle of His) splits into the right and left AV bundles.

Finally, the signal arrives at the Purkinje fibers which are connected to contracting cells. Purkinje fibers, like the cells of the SA node, behave like neurons. The Purkinje fibers are located along the sides of the ventricles and lead to the apex (tip or bottom) of the heart. From the apex, the contraction travels up and through the rest of the heart.

Intercalated discs, or desmosomes, connect the cardiac cells and allows the contraction to travel.

Summary

Frank Starling Reflex →SA Node →Internodal Fibers →AV Node →AV Bundle (Bundle of His) →Right and Left AV bundles →Purkinje fibers →apex →contraction

This is the chart I made for myself in order to memorize the steps and it works well.

Another important aspect to remember is that the cells in the SA node and in the Purkinje fibers behave more like neurons than muscle cells.

If you remember these points, you will know the basics of a heart contraction.

About The Author Kristen Williford

Hi everyone,my name is Kristen. I am a pre-med student studying Biology and Spanish. I'm also a beauty blogger, active volunteer, coffee lover and avid reader. I hope you enjoy my articles and find them informative.

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Yes, the kidneys are important for excretion, however they play more vital roles to life than we realize. The kidneys perform the following functions:

1. Regulation of Arterial Blood Pressure

The kidneys excrete a great amount of sodium and water. They secrete an enzyme called rennin that activates the renin-angiotensin system that control blood pressure and sodium concentration.

Blood pressure

2. Regulation of water and electrolyte balance

In order for our bodies to maintain a balance, the amount of water and electrolyte we take in must be the same amount we excrete. If we take in more than we excrete, the kidneys will work to regulate the excess and bring the body to a balance.

Balance

3. Excretion of metabolic waste products and foreign chemicals

Our bodies, each day, form waste products that it does not need. These products include urea, creatinine, uric acid and waste products from the breakdown of hemoglobin that give the urine the color it has.

If these products are not eliminated from the body as fast as they are produced they become very harmful to the body. The kidneys remove these waste products so, our body can function normally.

4. Regulation of Red Blood Cell Production

Our kidneys secrete erythropoietin, a hormone which stimulates the production of red blood cells in the body. If the kidney is removed or severely damaged, then we may not be able to produce RBC and severe anemia will develop as a result of the decrease in the production of erythropoietin.

5. Regulation of Vitamin D Production

Our kidneys produce the active form of vitamin D, calcitriol. We get vitamin D from sunlight or from ingested vitamin. These types of vitamin D are in their inactive form. The kidneys are needed to convert them into their active forms.

Regulation of Vitamin D

The active form (calcitriol) is necessary for normal calcium absorption in the bone. Therefore, if the kidneys are damaged there will be a decreased level in calcitriol which then will lead to a reduction in calcium absorption, and thus low calcium in the bodyleading to bone disorders.

6. Gluconeogenesis

If we should stop eating carbohydrates (our main source of glucose) for a day, our bodies would begin to form new glucose from the amino acid in the proteins we intake. This process is known as gluconeogenesis.

So, when the kidneys are damaged, this function is crippled, and this can cause death within a few days.

7. Regulation of Acid Base Balance

The kidneys are able to perform these functions through the work of the nephrons and the collecting tubules.

In the next section we will discuss the role of the nephrons.

About The Author Sonya McKenzie

I am currently a "50% doctor." You might be wondering what that means. Well, I am currently in my last few weeks of my second year in medical school. I love anything to do with science and medicine. I have great interest in medicine from the preventive aspect.

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However, the main strong point of AIDS, its main distinguishing feature is that it is unpredictable. It can activate now, or later, or never. There are people who have died two months after contracting it. There are people who have been living with AIDS for a decade, or so. One thing we know for sure — AIDS is lethal.

AIDS

AIDS is also known as Acquired Immuno Deficiency Syndrome. We can break it down as follows:

Acquired: obtained i.e. something that is not natural and has happened due to some external factor.

Immuno Deficiency: Considerable decrease in the ability of your body to fight disease or decrease in the immunity of your body due to something. That “something” in this case is a Virus specifically HIV virus.

Syndrome: Disease.

Therefore, AIDS can be summed up as the unnatural decrease in the ability of your body to fight diseases. Let’s say a highly praised artist suddenly starts forgetting how to paint. Unnatural isn’t it?

HIV

AIDS is caused by a retrovirus known as Human Immunodeficiency Virus. Its has RNA instead of DNA. This virus like all other viruses is just another particle in the surroundings, but once it enters our body, it progressively becomes active and multiplies. To do so, it requires the help of a white blood cell or a leucocyte.

One of the distinguishing features of this virus is that it doesn’t activate as soon as it enters the body. It may or may not remain static. Hence, an HIV-positive person may not always have AIDS.

How does HIV virus infect the host cell?

HIV entry into T cell

HIV, when looked through a microscope looks like a very fuzzy ball. This ball or the virus lands itself on the WBC and enters into it. It goes directly to the nuclei and begins manufacturing viral RNA which is then integrated into the original DNA.

The most common WBCs are T4 lymphocytes or CD4 cells. It also infects monocytes, macrophages and microglial cells of CNS.

Think of the nucleus as a kitchen, and the DNA as the book of recipes. These recipes enable the nucleus to produce a variety of enzymes and perform a number of functions essential to the human body.What this virus does is alter the recipe book so that instead of producing the enzymes and performing functions, it now produces more HIV virus.

HIV Infection in Target Cells

The provirus DNA, when activated, starts producing virus until it bursts due to the sheer number of virus inside it, hence leading to two things:

1) Destruction of the cell and;

2) Large number of newly produced HIV viruses which repeat the process all over again and thus spreading infection.

Why is it lethal?

Due to disruption in the original function of WBCs (protecting the body) and their eventual elimination, the disease resisting capacity of the body goes down and body becomes vulnerable to more and more diseases.

The patient, due to low immunity, quickly acquires various diseases like pneumonia, tuberculosis, cholera, malaria, Kaposi’s Sarcoma, etc, which heals extremely slowly since the body is unable to fight back and eventually dies due to these diseases.

Therefore, HIV virus indirectly makes the human body susceptible to hundreds of other opportunistic diseases, which later leads to the death of the human body.

About The Author Srushti Kumbhare

Hey everyone! I'm Srushti. I'm a science student. I love biology, knowing how things work inside things, that every system has various systems in it. Biology is full of wonder and it is one of my favorite hobbies. I really hope the articles are helpful. If you have any questions, I'll be happy to help. :)

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Now that we’ve introduced the coolest cell in the body, and the army supporting it, let’s start our descent into the nervous system.

Our experience of the world starts with the ability to perceive the world, and to discriminate between different kinds of stimuli. You generally experience the world through your five senses: vision, hearing, smell, taste and touch. Each of these senses require their own type of “perceiving” neurons.

But you also have a (forgotten) 6th sense…

… no, it’s not your intuition or anything metaphysical….

It’s called proprioception: the ability to know where your limbs are in space, without having to look at them.

OK, let’s use the correct vocab here. “Perceiving” neurons are actually a class of neurons on their own properly called Sensory Receptors.

Add to that your 7th sense (man, you never knew you actually had an extra pair of totally real senses), which perceives the internal surfaces of your body, such as your blood vessels and the walls of your viscera. This perception is possible because of interoceptors – a type of sensory receptors.

The Sense of Touch

Your body is covered with skin tissue, which means that your sense of touch is usually a result of your skin contacting a surface.

There are 5 types of stimuli that can be perceived by the skin

Skin Stimuli:

Sensory Receptors of the Skin

Skin Sensory Receptors - Credit: Thomas.haslwanter

They can perceive pain, touch and temperature. They can be found in the epithelial layer of the skin.

They respond to light pressure. They can be found in the epithelial layer of the skin. They can perceive fine differences in location, a process known as two-point discrimination. (This is what enables people to read Braille with their fingers).

They wrap around hair in the skin and they can perceive when the hair on your body or face is being touched.

They respond to touch and pressure. They are found deeper within the skin, in the subcutaneous layers. They are known to be sensitive to changes in angle, and as such, they also carry a proprioceptive role involved in telling the brain where the fingers are located in space.

They too are involved in two-point discrimination. They are usually found in the “hairless” portions of your skin such as the palm of your hand and your fingers.

They are sensitive to pressure and vibration. It’s the biggest type of nerve ending. In fact it’s so big that it can be seen by the naked eye!! They are characterized by a large, flat laminated “disc.” They are found deeper within the skin (this is the reason why they respond so well to pressure).

That’s it for this overview of the sensory receptors of the skin. Stay tuned as we will cover the sensory receptors for other senses in the weeks to come.

Minimum to Remember:

If you want more articles and videos about the Nervous System, you can find them here. More resources are available to help make Biology fun. I invite you to absorb all the content you can find here at Interactive-Biology.com.

About The Author Mag Reves

Hi, I love to talk about, neuroanatomy, psychology, memory,... and pretty much anything related to the brain. I graduated from UCLA with a degree in Neuroscience and I also run another website dedicated to helping Pre-Meds become great medical school applicants.

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Calorie Facts

A calorie is a unit of measurement, specifically: energy. It is the amount of energy needed to increase the temperature of 1 gram of water by 1°C. However this isn’t the same calorie you hear so much about!

In terms of nutrition and every day use, using the calorie would lead to exorbitant numbers (think of having something so large as a 20,000 calorie diet, yikes!) For diet purposes, the Calorie was invented. Instead of the amount of heat required to raise 1 gram of water by 1 °C, the Calorie is the amount of heat required to raise 1 kilogram of water by 1 °C . For simplification purposes however, it’s assumed that whenever talking about nutrition that the Calorie is being used no matter the capitalization.

But I know I know, enough about numbers. What does these all mean for me and my body?

Well, as you know, every day we eat numerous types of foods (sandwiches, pasta, hamburgers) and imbibe various types of liquids (waters, juices, sodas). These all contain numerous amounts of molecules in the form of proteins, carbohydrates and fats. When we eat these things, our body converts them to fuel for our everyday use. Just how much energy these foods give us is defined as a calorie, and different foods give us different amounts of energy.

Slice of Cake

The exact amount of energy depends on the molecules present in the food, and at what amounts. Carbohydrates and protein both give 4 calories per gram, while fat gives more than double that, at 9 calories per gram. It’s easy to see now why a slice of cake with carbohydrates and fats has a lot more calories than a slice of bread with just carbohydrates, isn’t it?

So what happens if you consume more calories than your body needs?

You gain weight! Just how much depends on exactly how many calories you consumed in excess, along with a bunch of other factors such as personal metabolism. This relationship works the opposite way, as well — if you use more calories than you consume you’ll lose weight, as your body needs to break down the stored fat for energy.

On top of that, everyone has different calorie needs. At the basic level we need a certain amount of calories just to sustain normal upkeep of our body– like keeping our hearts beating and our brain thinking.

But the amount of calories a person needs is also dependent on gender: men tend to need more calories than women. Activity level also has a big effect on calories as well. A marathon runner needs a lot more calories than an office worker! You can now see why it’s hard to find a calorie value per day that’s suitable for everyone, with everyone having different body types, different level of activity, and different levels of metabolism.

As a general rule however, a person should consume about 2000 calories per day (this is why you see nutrition facts based off of a 2000-calorie diet). This amount isn’t tailored exactly for your specific needs though– you’d need to do some calculations or see a registered dietician to figure out just exactly how many calories your body needs on average. That being said, 2000 calories a day is a good general guideline to follow.

About The Author Christine Cemelli

22 and currently studying towards a Masters in Nutrition & Dietetics at New York University. I have my bachelors degree in Psychology and have an interest in researching what exactly effects food choices. I also love video games!

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Behind every successful man is an even more successful wife?

The same concept applies to neuroglia:

• Glial cells are the unsung heroes without which neurons would be totally useless and unable to survive.

Behind every successful neuron is an “army” of even more awesome glial cells. — MagR

So today we’re gonna do a rundown of the glial cells!

Neuroglia: Function and Definition

First, let’s make things clear:

Neuroglia = Glia = Glial cells (yes, with an L at the end).

Three different names referring to the same type of cell. (I used to be quite confused until I finally realized that these are three names referring to the same object–as if there weren’t enough words to remember in neuroanatomy as it is…)

Neuroglia are way more numerous then neurons; “an army for a commander.”

 Neuroglia Function

1. Support Nutrition: Some glial are involved in providing the neurons with nutrients by transporting molecules from the blood to the neuron. (Satellite cells and Macroglia)

2. Poison Defense: Some glial cells support the role of “blood brain barrier.” They will simply block most harmful substances from ever reaching the neuron. (Without this barrier, most molecules in the blood would become deadly poisons!)

3. Support electrical communication:

a. Ion concentration regulator: Neuroglia regulate the amount of ions around the neurons. As such they make sure that the neurons environment is optimal for the transmission of the electric pulse. (Learn more about electric signal conduction)

b. Myelin Sheath creation: Some glia are responsible for creating and repairing the myelin sheath around the axon of the neuron. The myelin sheath is what ensures fast / salutatory propagation of the electric signal) (Oligodendrocyte and Schwann cells)

4. EMT services: Some neuroglia proliferate and rush to a site of injury within the central nervous system. (Microglia)

5. Other functions, including structural function, that we will not go into detail.

Types of Neuroglia

Are you ready to absorb even more vocab? Here we go!

In the Central Nervous System (~in the brain)

Cells of the Central Nervous System

Here we have 3 main types of glial cells (Macroglia, Microglia and Ependymal glia) with sub-categories and sub-sub categories:

A. Macroglia

• Macro – stands for “big.” These cells are “bigger” than other glial cells.

Macroglia are divided into two sub-categories: The Astrocytes and the Oligodendrocytes.

1. Astrocytes

As the prefix implies – Astro means star, astrocytes look like stars with lots of branches (look similar to dendrites – but they are NOT dendrites!)

Astrocytes have two sub-categories themselves:

a. Protoplasmic astrocytes

 They are found in the gray matter

b. Fibrous astrocytes – They are found in the while matter.

2. Oligodendrocytes

The prefix “oligo” means “few”, and “dendro” sounds like “dendrites”. Basically this cell looks like an astrocyte except that it is a little smaller, and has only a few branches.

Oligodendrocytes have 3 sub-categories (I told you this would be tough – I’ll try to make it short!):

a.  Satellite oligodendrocyte – Myelin sheath creation

b. Interfascicular oligodendrocyte – They are found in between axons (“inter”) and can “myelinate” more than one axon at a time.

c. Vascular oligodendrocyte – They are found close to small capillaries.

B. Microglia

These are the smallest types of glia (they are micro!) This small size is what allows them to proliferate around a site of injury in the CNS

C. Ependymal glia

They are involved in neuronal development.

• Mnemonic for the CNS: ”Mark And Peter Found Online Some Indian Veal – Micro Epic.”

(Macroglia Astroctyte Protoplasmic Fibrous Oligodendrocyte Satellite Intrafascicular Vascular – Microglia Ependymal)

We’re almost finished! We only have two types of neuroglia left in the Peripheral Nervous System (PNS).

In the Peripheral Nervous System (~spinal cord)

A. Satellite cells (don’t confuse them with the satellite oligodendrocytes). These have similar functions as the Macroglia we just covered.

B. Schwann cells – (I love the name… Sounds so pretty). These glial cells are responsible for creating and repairing the myelin sheath of axons in the PNS. They can only myelinate one axon at a time

OK! We’re done!

Minimum to Remember About Neuroglia

• Neuroglia = glia = glial cells = the reason why neurons can survive, function, and be successful!

Their function:

1.  Support nutrition
2.  Poison Defense
3.  Support electrical communication
4.  EMT services
5.  And much, much more….

Types of Neuroglia

- too many!

• Once you remember the name and what they mean you can recall 90% of what we just covered. Use the chart I prepared for you if it helps!

Mnemonic for neuroglia in the CNS: Mark And Peter Found Online Some Indian Veal – Micro Epic.

If you want more articles and videos about the Nervous System, you can find them here. More resources are available to help make Biology fun. I invite you to absorb all the content you can find here at Interactive-Biology.com.

About The Author Mag Reves

Hi, I love to talk about, neuroanatomy, psychology, memory,... and pretty much anything related to the brain. I graduated from UCLA with a degree in Neuroscience and I also run another website dedicated to helping Pre-Meds become great medical school applicants.

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The ureters are small muscular tubes about 25-30cm long that carries urine from the kidneys to urinary bladder through a peristaltic movement. The ureters emerge from the tip of the renal pelves at the hilum of the kidney.

After exiting the kidneys, the ureters run in front (anterior) of the psoas major and pass over the brim of the pelvis at the bifurcation of the common iliac arteries and enter the fundus of the urinary bladder.

Major Constrictions of the Ureter

The ureters have three major constrictions that occurs at the:

1.  Renal pelvis: At the junction of the ureters and renal pelves.
2.  Pelvic brim: this is when the ureters pass the brim of the pelvic inlet at the bifurcation of the common iliac artery or the beginning of the external iliac artery.
3.  Ureterovesticular junction: this is during the course of the ureter through the urinary bladder.

These major areas of constriction are sites for potential obstruction of kidney stones.

A point to note: the ureters run differently in females and males. In females the ureters runs below  (inferior) to the uterine artery.

The ureter gets it’s blood supply from the:

Ureter Blood Supply

• renal arteries
• Gonadal arteries
• Common iliac a
• Uterine or inferior vesical arteries
• Middle rectal artery

About The Author Sonya McKenzie

I am currently a "50% doctor." You might be wondering what that means. Well, I am currently in my last few weeks of my second year in medical school. I love anything to do with science and medicine. I have great interest in medicine from the preventive aspect.

• 

What are lymphocytes?

The chief cells of the Immune system, the real soldiers of the inherent army of our body are known as lymphocytes. A healthy person has about a trillion lymphocytes in his body. There are two types of Lymphocytes:

• T lymphocytes (T cells) and
• B lymphocytes (B cells)

Where do they come from?

Hematopoiesis of Blood Cells

Like a majority of blood cells, these cells are produced in our bone marrow by a process called hematopoiesis (heamato means ‘blood’ and poeisis means ‘to make’). More specifically, the process may also be called lymphopoiesis.

Now, both these cells are produced in the bone marrow from pleuripotent stem cells. Each of these cell brothers have a destiny. Some of them go on to become thymocytes, also known as T cells and others stay for some more time and become B cells on maturation.

T cells

Those cells which go on to become thymocytes migrate to thymus gland to mature i.e. fully develop. After maturing, they migrate via blood and lymph to the secondary lymphoid organs which are the sites of lymphocytes activation that take place through interaction of surveillance cells with antigens; similar to a headquarter from which orders for action are given.

T lymphocytes generate cell-mediated immunity. Cell-mediated immunity is an immune response that does not involve administration of chemicals or bodily biological bombs or poison but actual deployment of other soldiers like macrophages to the site of infection. T lymphocytes called cytotoxic T-cells directly attack invading pathogens. They also destroy infected body cells and cancerous cells.

Antigen- presenting cells

There also exists a subgroup of T cells known as T helper cells, which  interact specifically with the antigen and become activated. These cells now dispatch from the lymphoid tissues and circulate along with blood. These cells produce chemical substances called lymphokines (a kind of antigen poison) to eliminate the antigens.

B cells

Now B cells are also produced in the bone marrow, mature in the bone marrow itself for a greater period of time than T cells. However, after some time, they too migrate to secondary lymphoid organs to mature properly.

These B cells then perform the function of immune surveillance. They do not produce antibodies until they become fully activated.

Once these cells are activated, they produce and secrete a large amount of substances called antibodies which bind to the antigen; just like you add meat to make anything attractive for a dog.

Due to these antigens, a large amount of macrophages get attracted to the specific antigen and destroy it. They are also sometimes known as antibody factories.

Even B-cells are of various types. They are:

1. Plasma B cells (also known as plasma cells, plasmocytes, and effector B cells);
2. Memory B cells (Live for a long time and are responsible for maintaining all the data related to previous infections like type of virus, how it was eliminated, which antigens are produced, etc. and also for giving executable orders for recurring infections);
3. B-1 cells;
4. B-2 cells;
5. Marginal-zone B cells, and
6. Follicular B Cells.

About The Author Srushti Kumbhare

Hey everyone! I'm Srushti. I'm a science student. I love biology, knowing how things work inside things, that every system has various systems in it. Biology is full of wonder and it is one of my favorite hobbies. I really hope the articles are helpful. If you have any questions, I'll be happy to help. :)

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Encephalitis is an acute inflammation of the brain. When I say encephalitis, it doesn’t include meninges affection. When meninges are affected, it’s called meningo-encephalitis.

Incidence of 4-7 per 100,000 persons per year.

The cause of encephalitis is usually infectious in nature. Although bacteria, fungi, protozoa can produce encephalitis, most cases are viral in origin. There is over 100 viruses worldwide that can cause encephalitis, the most important of them are the following:

1. Herpes Simplex Virus (HSV)
2. Varicella Zoster Virus (VZV)
3. Rabies
4. HIV
5. H5N1 encephalitis
6. ArBoVirus encephalitis (Arthropod-Borne viruses) are subdivided into:

• Flaviviridae (Japanese encephalitis – St. Louis encephalitis – West Nile virus)
• Togaviridae (Eastern equine encephalitis – Western equine encephalitis)
• Bunyaviridae (La Crosse encephalitis)

Parasitic infection as toxoplasmosis, malaria, PAM (caused by Nagleria fowleri) or GAE (caused by Acanthamoeba castellanii) can cause encephalitis in immuno-compromised patients.

Bacteria like streptococci, pneumococci, staphylococci can cause ceribritis (inflammation of cerebral cortex). Bartonella henselae (causing cat-scratch disease) or Borrelia burgdorferi (causing Lyme disease) may cause encephalitis too.

Cryptococcus neoformans is a fungus notorious for causing fungal encephalitis in the immuno-compromised.

Pathogenesis

Let’s know how causative organisms (specially viruses) can lead to inflammation of the brain:

1. The virus replicates outside the CNS.
2. Enter CNS by hematogenous spread or along neural pathways (eg, rabies virus, HSV, VZV).
3. Once across BBB (Blood Brain Barrier), the virus enters neural cells, with resultant disruption in cell functioning, perivascular congestion, hemorrhage, and a diffuse inflammatory response.

• Regional tropism: It was found that some viruses have more affinity to a particular part of the brain, causing inflammation in that specific part only! That occurs due to neuron cell membrane receptors distribution that are  found only in specific portions of the brain, with more intense focal pathology in these areas. A classic example of regional tropism is the HSV predilection for the inferior and medial temporal lobes.

Clinical Picture

• Adult patients: acute onset fever, headache, confusion, seizures.
• In severe cases: nausea, vomiting, sensitivity to bright light and coma.
• Infants may present irritability, poor appetite, fever, body stiffness and bulging fontanelle.

Diagnosis

• Neurological examinations: reveals a confused patient with stiff neck, due to the irritation of meninges.
• Detection of antibodies in the CSF against a specific viral agent or by PCR.
• Serological tests may show high antibody titre against the causative antigen.
• Examination of the CSF obtained by lumbar puncture usually reveals increased amounts of protein and WBCs with normal glucose.
• Bleeding is also uncommon except in patients with herpes simplex type 1 encephalitis.
• In patients with herpes simplex encephalitis, EEG may show sharp waves in one or both of the temporal lobes.

Treatment

• Acyclovir (anti-viral) for HSV
• In advanced cases, supportive treatment, such as mechanical ventilation, is usually needed.
• Corticosteroids are used to reduce brain swelling and inflammation.
• Sedatives may be needed for irritability or restlessness.
• For Mycoplasma infection, parentral tetracycline is given.
• Encephalitis due to Toxoplasma is treated by giving a combination of pyrimethamine and sulphadimidine.

Vaccination

• There is no vaccine for most encephalitides until now.
• A live, attenuated vaccine against Japanese encephalitis virus has been developed and tested in China and appeared to be safe and effective.

About The Author Ahmed Reda Abolmaaty

Hi, I'm Ahmed. I'm a medical student at Mansoura School of Medicine, Egypt. I love many fields of science, not just biology. I can help you understand anything in math, physics, and chemistry too xD I hope you like the articles I write here at Interactive Biology. If you have any questions, please don't hesitate to ask :)

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If there is even a minute problem in this amazing system itself, it can lead to discomfort, disease or may even prove fatal.

Allergies

Let’s say, our immunity defense system has some internal problems. How does it lead to death or disease by the disease mechanism itself? It can occur through three ways:

1. Hypersensitivity,
2. Immunodeficiency, and
3. Auto immunity

 Hypersensitivity (also known as “allergies”)

Here, the body troops (leucocytes) respond extensively to a particular foreign substance leading to damage and excessive inflammation in various parts of the body. This is what primarily causes rashes, swelling and itching, the main symptoms of an allergy.

For example, let’s say, the troops, here leucocytes, are perfectly normal when the person has fruits like banana or strawberries. But, the moment he has a mango slice, the troops declare a high alert and rush to the spot with all their weapons. Thus, the person experiences itching sensation in his throat and even gets rashes all over his body.

Allergic rash

An excessive and inappropriate immune response to a specific foreign substance is known as an allergy. It is also defined as an acquired abnormal hyper immune response to a foreign substance during first and subsequent occasions.

Prerequisites for body to trigger an allergic reaction are:

1. The body must come into contact with the allergen
2. Sensitization of the body must occur for the allergy to take place.

How does sensitization of the body occur?

Suppose there is a guy named Bob. Once upon a time in Bob’s childhood, he experienced mild food poisoning due to arsenic in his food. Thus, the body had come in contact and successfully encountered foreign substance (arsenic in this case) and retained this memory. So, the body, from now on, views arsenic as a major threat.

Now after ten years, Bob tries clams for the first time. And, immediately after a few bites, he starts feeling queasy. Why so? Because majority of edible Crustaceans contain small amounts of arsenic which is safe for human consumption. However, when Bob ate the clams, his body immediately declared high alert and activated a full- blown immune response.

Thus, here, Bob discovered upon going to the doctor that he indeed is allergic to clams. His body has already fulfilled the two pre-requisites for an allergy to occur and that’s precisely what happened when he had clams. Bob, therefore, has officially developed an allergy.

Types of Allergic responses:

There are four types of allergic responses that are triggered by various immunoglobins in the body. They are:

Type I hypersensitivity is an immediate or anaphylactic reaction.

Symptoms of type 1 hypersensitivity normally range from mild discomfort to death. What happens here is  due to excessive stress from allergens given by their supposedly supervisor enzyme Immunoglobin E, the mast cells and basophils lose it and begin to degranulate i.e. they begin to randomly eject granules out of their body mass which is definitely not normal under any circumstances. When this occurs on a really large scale, the person dies.

Type II hypersensitivity

This type is similar to auto immunity, however it is largely dependent on the antibody (poison) action. What happens here is, the antibody, instead of binding to foreign body, binds to its own antigen, thus leading to cell destruction. It is triggered by Immunoglobin G and Immunoglobin M antibodies.

Type III hypersensitivity reactions

 Also known as Immune complex hypersensitivity, it is similar to type II hypersensitivity.  The reaction may be due to an internal or external factor and is usually triggered by Immunoglobin G. The major damage done is on neutrophils and platelets.

Type IV hypersensitivity 

Type IV hypersensitivity (also known as cell-mediated or delayed-type hypersensitivity) usually takes between two and three days to develop Type IV reactions are involved in many autoimmune and infectious diseases, but may also involve contact dermatitis (poison ivy). These reactions are mediated by T cells, monocytes, and macrophages.

Some common Allergens are:

Dust, pollen, spores, moulds, feathers, fur, nutrients, cosmetics, perfumes, venom, vaccines, and drugs; physical agents like cold, heat, radiations and even microbes, and a lot more.

About The Author Srushti Kumbhare

Hey everyone! I'm Srushti. I'm a science student. I love biology, knowing how things work inside things, that every system has various systems in it. Biology is full of wonder and it is one of my favorite hobbies. I really hope the articles are helpful. If you have any questions, I'll be happy to help. :)

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Muscles of a Running Man

Location and Locomotion of Muscles

There are two important terms to know when referring to location of muscles. The first is somatic, which refers to muscles that are directly associated with moving the body. These muscles can be controlled and are considered to be voluntary. An example of a somatic muscle would be the diaphragm.

The second type is visceral muscles. Visceral muscles include the blood vessels and gut, and they are usually smooth. Visceral muscles are not voluntary. Somatic vessels are usually, but not always, associated with the appendicular skeleton (the limbs) and visceral is typically associated with the axial skeleton (center of the body, or the axis.)

There are also different forms of locomotion related to muscles. The first type is saltational, which refers to having powerful legs and having forelimbs different from the hindlimbs. An example would be a cat or dog. The next type is cursorial, which means that the organism has no real muscles in the fingers and toes. Humans would be an example of this.

Finally, there is aerial locomotion. These organisms, such as birds, have a reduced spine and more bone fusion. Otherwise, birds would constantly be working against themselves and would not be efficient fliers. Organisms may not belong to only one category, but may belong to more.

Cell Types: What Makes Them Unique?

Smooth Muscle cells

The types of muscle cells are very interesting because there are many similarities, but there are also many differences. Smooth muscle is the most unique because it has very little in common with the other types. It is weaker and less organized. Smooth muscles can be found in your stomach and intestines.

Like cardiac muscle cells, contraction of smooth muscle is involuntary and uninucleate. Cardiac muscle cells have a few unique characteristics including automaticity and autorhythymicity. Automaticity means that the single cells of the heart are able to contract on their own and autorhythymicity means that the contractions of the cells are synchronous.

Furthermore, cardiac muscle cells also have intercalated disks, or desmosomes, that allow the cells to stick together. Skeletal muscle cells and cardiac cells have striations (or divisions) but that is where the similarities end. When you think of muscles, the image that comes to mind is most likely a skeletal muscle. These muscle cells are long and have many nuclei. An example of a skeletal muscle would be your triceps and biceps.

Muscle Anatomy and Contractions Made Simple

Muscle contractions are controlled by the muscle fibers, which are composed of muscle cells. One important thing to remember about these fibers is that strength is not equal at all lengths. In general, shorter muscles are stronger. Length allows speed, which is a result of the sarcomeres (functional unit of the muscle cell) contract at the same speed, but a long muscle, such as in your legs, can cover a larger distance in a short amount of time.

Insertion of the muscle also has an impact. If the insertion is distal (farther from the body’s axis) the muscle is stronger but slower. Likewise, if the insertion is proximal (closer to the body’s axis), the muscle will act faster, buy will not be as strong. A stimulation frequency exists that allows muscles to only use the amount of energy that is needed.

Muscle contractions begin in the central nervous system, and this applies for voluntary and involuntary movement. This causes a motor neuron (a nerve cell specific to movement) to activate. The axon of the neuron carries a signal (called an action potential), which is taken to the ends of the muscle fibers.

Next, a neurotransmitter called acetylcholine (or ACH) is released and causes the action potential to travel through the muscle fibers. Finally, calcium ions are released, which triggers troponin and tropomyosin to move along the fibers. All of these steps lead to the contraction of a muscle. It is also important to remember that all muscle types contract in a similar manner.

Muscles also exhibit something called fused tetanus. This term is used to describe a muscle that is unable to relax between impulses. The contraction steps are complicated, but this gives you the most important information about how muscles allow us to move.

Now, you have all the basic knowledge of the muscular system and probably some information you may not have known. The subtle differences between cell types and locomotion are part of what makes the system interesting, and efficient. I hope you enjoyed reading and learned something new.

About The Author Kristen Williford

Hi everyone,my name is Kristen. I am a pre-med student studying Biology and Spanish. I'm also a beauty blogger, active volunteer, coffee lover and avid reader. I hope you enjoy my articles and find them informative.

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It takes focus and action to reach any goal yet there are always a few key tips to keep in mind as a strategy to get you there.

Tip #1: Know your learning style.

We are like fingerprints; there are no two alike, even with identical twins. There are a variety of learning style models, yet the one we will discuss in this article is the Fleming’s VAK model (VAK stands for Visual Auditory Kinesthetic):

VISUAL learner: Use charts, maps, filmstrips, notes and flashcards. Practice visualizing or picturing words/concepts in your head. Write out everything for frequent and quick visual review.

AUDITORY learner: Record lectures to help you fill in the gaps in your notes. Listen and take notes, reviewing notes frequently. After you have read something, summarize it and recite it aloud.

KINESTHETIC/TACTILE learner: Trace words as you are saying them. Write out facts several times. Keep a supply of scratch paper for this purpose. Taking and keeping lecture notes will be very important. Make study sheets.

Take your FREE learning style quiz!

Tip #2: From big picture to details.

In order to understand the details, you may have to step back and get a bird’s eye view to truly put the pieces together.

Do you remember piecing together jigsaw puzzles? No, not the virtual ones. The cover of the box was typically a picture of the finished puzzle. Inside the box were tiny puzzle pieces waiting to be snapped together. What if the box had a big question mark on the cover? Wouldn’t it make it a tad bit harder to piece the puzzle together? It is always nice to have a road map. This is very important for visual learners.

Tip #3: Trust yourself.

Trust your study techniques and trust that when you are ready to take the exam or practical. You would not have made it to where you are now if you were not smart and capable human being.

Stress can cause you to temporarily forget what you have spend all that time learning. So, take two or three deep breaths, and think about the fun plans you have made or something funny to distract you from becoming too stressed about your upcoming exam.

You’ve studied for at least a day! Hey, I am not condoning cramming the day before an exam yet I want to be realistic. When you are taking 5 classes or more a semester or quarter, it is impossible to cover every single detail. If you have seen it, read it, smelled it, and heard it; it is in your head, snuggled in your brain.

Do you remember that semester of Spanish you took 3 years ago? You have not used it in, let’s say, 3 years, and when you hear someone speak Spanish or you read written Spanish, it mysteriously makes sense. You have that memory connection, it did not vanish into thin air. Practice will only strengthen the connection! You know it, simply have faith!

Tip #4: Be present.

Stay present when taking the exam. This means, you do not focus on what you should have studied or how hard the questions are. Reassure yourself! Skip the questions you do not know and come back to them. Other questions and answers may trigger your memory. Bring ear plugs to block out any noise distractions.

Tip #5: Reward yourself.

Eat a good breakfast, a hearty protein and fiber based breakfast works wonders. This is very important as our body needs the basic nutrients we receive from food to function properly. You are what you eat!

Make a list of fun and enjoyable activities. After each study session or exam, choose something from your “fun” list to check off. Don’t take this lightly. Who says you have to wait until the end of the semester or quarter to celebrate!

In a nutshell..

You know yourself the best! Pay attention to what makes you unique. What study techniques did you use when you aced your last exam? Keep notes so that you will know what is working and what does not work for you.

Our education system was traditionally based on auditory learning yet this is rapidly changing, mainly with the internet. Do not be afraid to seek out information that better suits your learning style.

Have fun!

About The Author Stacy Mobley

Hello, I'm Stacy, a 4th year Naturopathic Medical student, who loves sharing my knowledge and "ah ha" moments! I'm very passionate about empowering others to truly understand how amazing their body is, how to cherish and protect it ;-) Follow me on twitter: @dairyfreenow

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The lungs are surrounded by a double membrane called pleura. This membrane has two layers, a parietal pleura and a visceral pleura. The parietal pleura is attached to the chest wall and the visceral pleura covers the surface of the lungs. Between these layers of pleura is a potential space i.e. a space that doesn’t exist but it could exist if something goes wrong. There is a small amount of fluid in this potential space, this serous fluid acts like a lubricant.

The purpose of the pleura is to allow the lungs to move inside the body cavity without friction as friction would cause damage to the lungs and the tissue in the chest wall. Imagine that if you got an empty balloon and put a few drops of a lubricant such as olive oil inside it. You can rub the two sides of the balloon against each other very smoothly and easily. 

Pressure and inspiration

The intrapleural pressure, that is, the pressure in between the two layers of pleural membrane is -4mmHg. What? But that’s not possible. How can you have negative pressure?

Technically, it’s not negative pressure, it’s just less than atmospheric pressure. (Atmospheric pressure is approximately 760mmHg, intrapleural pressure is 756mmHg.) This pressure difference keeps the lungs ‘stuck’ to the chest wall so they don’t collapse.

The lungs can expand because of compliance, the ability of the lungs to stretch. This is different to elasticity which is the tendency of your lungs to spring back to their original shape.

Healthy people’s lungs are always partly stretched, if they were fully collapsed, we would never be able to breathe. You might ask, “Why?” Because of surface tension.

Alveoli

As you may know, the lungs are filled with little sacs called alveoli; this is where gas exchange occurs. In order for this to happen, there is a thin layer of liquid on the surface of each alveoli to help the gases dissolve and move across the membrane. This poses a problem: surface tension.

You may have noticed surface tension before; a water droplet sitting on a leaf is dome shaped because of surface tension; all of the water molecules are attracted to each other. The problem with this is that too smooth wet surfaces that are stuck together are a lot harder to pull apart than if they were dry. If you’ve ever stuck two microscope slides together with water in the middle, they are very hard to separate.

This means that if an alveoli is completely collapsed, it is extremely hard to open again. To give it a bit of a hand, our alveolar cells make a substance called surfactant (this is a lipoprotein.). This substance lowers surface tension and makes it a lot easier for alveoli to open if they collapse. (A bit of trivia, babies that are born very prematurely can’t make surfactant and must be given artificial surfactants to help them breath.)

Even with surfactant, it still takes a lot of effort to open all the alveoli so it is advantageous not to have the lungs collapse fully.

So, how do we breathe?

You breathe by expanding your chest wall and contracting your diaphragm. Your diaphragm is a big thin muscle that sits under your lungs and heart. The diaphragm pulls your lungs downwards and your chest wall pulls outwards and upwards – this causes your lungs to stretch and pull air inside. When you relax, the elasticity of the lungs pushes air out.

I hope this has helped show how the lungs work to pull in air and the factors that aid them in keeping us alive.

About The Author Christine Wickham

I am a second year medical student studying at Monash University in Australia. I am passionate about medicine and I love to share my knowledge with others!

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Smaller Structures Inside The Neuron

Like most cells, the neuron contains:

1. A nucleus - that contains the chromatin and the genetic make-up of the organism. The nucleus is generally located in the soma of the cell.

But, did you know that the nucleus in a neuron can “travel?”

• Like we said, the nucleus is generally located in the soma, but if the neuron gets injured, the nucleus will be found at the extremity of the cell. (An eccentrically located nucleus is a pathological sign of injured nerve tissue)

2. Mitochondria - a lot of it. The neuron is a very active cell that requires lots of energy

Did you know that your brain consumes 20% of your calorie intake?…
… Just for thinking!

Mitochondria can be found anywhere in the neuron but is mostly concentrated in the cell body and in the synaptic terminals.

3. Golgi bodies – to package proteins synthesized by the cell.

4. Endoplasmic Reticulum and Ribosomes to synthesize proteins.

Here is another really cool characteristic about the neuron: proteins synthesis can occur far from the nucleus!  In order to increase synaptic growth and the speed of information processing, so that you may learn and remember things faster, neurons can synthesize new proteins directly at the extremities

Sometimes, however, proteins cannot be made on the spot and they need to be transported from one part of the cell to a different part of the cell. In this case, the proteins can travel along “transport channels” such as microtubules, neurofilaments, and neurotubules.

Signal Alchemy In Chemical Synapses

Chemical Synapse (Credit: Nrets)

Zoom-In On The Presynaptic Terminal

The presynatpic terminal, at the end of the axon, is a very busy and active area.

• This is where the electric signal from the axon is transformed into a chemical signal (neurotransmitter) that can bridge the gap between two adjacent neurons.

The place is filled with mitochondria for energy, neurotransmitters in vesicles ready for release into the synaptic cleft, neurotransmitter fragments that have been endocytosed for recycling, and a plethora of other proteins and structures that would require a book to describe!

At this level, the cell membrane is filled with different types of ion-transporters.

• Every time a signal comes down from the axon, the electric pulse alters the polarity of the cell membrane. This forces ions (calcium–for example) tp rush into the cell, other ions will rush out of the cell, and the whole thing starts a fuss of activity resulting in the release of neurotransmitters in the synaptic cleft.

Zoom-In On The Postsynaptic Structure (at the dendrite)

• This is where the neuron receives the chemical information from the previous cell’s presynaptic terminal, and transforms it into a new electrical signal.

On this side of the synaptic cleft, the membrane is filled with different types of receptors (ionic and metabotropic receptors) that receive free neurotransmitters.

In some synapses, right below the membrane is a region called the postsynaptic density. It is called like this because it looks really “dense” on a microscope due to the amount of proteins that are present at this level.

Electrical Synapses – The Other Kind of Synapses

Electrical synapse (Credit: LadyofHats)

Did you know that the human body also contains “electrical synapses?” These synapses do not require neurotransmitters.

In electrical synapses, the two cells are so close  to each other that the electrical pulse can “jump” over the gap – the gap junction.

To keep the two cells close together, the membranes on both sides house protein structures called connexons. These channels can cross both membranes and are large enough to allow the diffusion of ions (i.e. the electrical signal) between these two cells.

• I invite you to read more about synapses and synaptic activity if you are totally enthralled by the magic of the synapse!

That’s it for this introduction to the neuron’s internal structure.

If you want more articles and videos about the Nervous System, you can find them here. More resources are available to help make Biology fun. I invite you to absorb all the content you can find here at Interactive-Biology.com.

About The Author Mag Reves

Hi, I love to talk about, neuroanatomy, psychology, memory,... and pretty much anything related to the brain. I graduated from UCLA with a degree in Neuroscience and I also run another website dedicated to helping Pre-Meds become great medical school applicants.

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What is Acquired Immunity?

Killer Cells and Antibodies

Acquired Immunity is the immunity that our body gains over time, similar to how an individual gains knowledge over time. However, our body learns how to target and destroy specific pathogens only when these pathogens invade our body. This knowledge and action performed by the body forms the Acquired Immunity.

Special features of Acquired Immunity

Acquired Immunity, unlike natural immunity doesn’t have natural barriers. However, what it does is generate special chemicals, also known as antibodies that neutralize the harmful toxins produced by the pathogen. Each specific type of pathogen requires a custom chemical to neutralize it. The major cells of acquired immunity are T lymphocytes and B lymphocytes. Also, acquired immunity of our body has some really surprisingly unique features. They are:

1) Specificity. Our body has the ability to recognize and differentiate various pathogens. It has a specific action for each type of pathogen. So, it is actually able to differentiate between different types of bacteria, whether it is harmful or not, and able to determine the best way to eliminate it.

2) Diversity. It can recognize a huge variety of micro-organisms from protozoa to advanced viruses.

3) Discrimination between self and non-self . It is able to tell apart the cells from our own body and other foreign particles or foreign cells. So after a transplant, patients usually have to take anti-rejection pills so that the body doesn’t reject the transplanted tissue. However, this does not hold true for blood transplant

4) Memory. Our immune system remembers each and every immunological encounter in our body. What this means is, once our body is invaded by a pathogen, it creates a specific response to that germ and eliminates it. It also remembers somehow this experience of fighting and the specific antibodies that are effective in destroying or eliminating the pathogen, so that the next time it enters, our body precisely knows the best possible way to immediately eliminate it.

About The Author Srushti Kumbhare

Hey everyone! I'm Srushti. I'm a science student. I love biology, knowing how things work inside things, that every system has various systems in it. Biology is full of wonder and it is one of my favorite hobbies. I really hope the articles are helpful. If you have any questions, I'll be happy to help. :)

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Normal Histology of Elastic tissue

Elastic fibers are widely distributed all over the human body specially in skin, tendons, cartilage, muscle, blood vessels, dura mater, and suspensory ligament of lens. The integral components of elastic tissue are called microfibrils. The major building block of microfibrils is called fibrillin which is a glycoprotein encoded by FBN1 and FBN2 genes.

Fibrilin contains a type of monomer called Ca2+binding Epidermal Growth Factor (EGF). Calcium binding to these monomers stabilizes the microfibrils, and subsequently stabilizes the whole elastic tissue while calcium loss or mutation of fibrilin causes the microfibrils to disintegrate leading to weakening of the elastic tissue.

What is Marfan Syndrome?

• It is the most common connective tissue degenerative disorder. It is an autosomal dominant inherited disease.

• As you know, we have 23 pairs of chromosomes, 22 of them are autosomal while the remaining pair is concerned with identification of your gender, XY or XX. Marfan syndrome has no relation with these sex chromosomes. It only occurs due to mutation in an autosomal chromosome #15.

• Marfan syndrome is named after Antoine Marfan, the French pediatrician who first described the condition in 1896.
  

  Abraham Lincoln

• Did you know that Abraham Lincoln (1809–1865), the 16th US President, is thought to have Marfan syndrome? Also, Nicolo Paganini, an Italian violinist and composer had Marfan’s.

Causes

Marfan syndrome results from mutations in the FBN1 gene (usually in the calcium-binding EGF portion) causing the microfibrils to lose their mechanical strength leading to:

1. Weakening of the aortic wall. Progressive aortic dilatation and aortic dissection occur because of tension caused by left ventricular ejection impulses.
2. Reduced structural integrity of the lens zonules, ligaments, lung airways and spinal dura.

Genetics

• If one parent is affected, there is a 1 in 2 (a 50:50) chance that a child will be affected.
• Marfan syndrome is a variable disease. So, a child may be affected less severely, or more severely, than his/her parent.
• If a woman with Marfan syndrome becomes pregnant, the pregnancy can put an increased demand on the heart that may increase the risk of aortic rupture.
• The mutant fibrillin-1 disrupts microfibril formation through the other fibrillin gene encodes normal fibrillin, that’s called dominant-negative mechanism.

Clinical Findings

If you are a doctor and a patient with Marfan comes to you, you can diagnose him/her depending upon many criteria in skeletal, ocular, cardiovascular system or any other system containing elastic tissues.

At first, we’ll discuss the skeletal findings of such patient. The patient  is usually taller and thinner than his/her family members. The following are some of the major criteria:

1. Severe pectus excavatum  or pectus carinatum(pigeon chest) in which the sternum is concave forward or convex forward respectively.
   

   Severe pectus excavatum

   

   Pectus Carinatum (Pigeon Chest)

2. Arachnodactyly: the fingers are longer and will look like a spider’s fingers (Arachno - “spider,” dactyly – “finger”).
   

   Arachnodactyly

3. Dolichostenomelia: limbs may be unusually long in proportion to the torso.
4. Scoliosis (Cobb angle >20°)
5. Reduced extension of the elbows (< 170°)

The following skeletal criteria are minor in Marfan:  Joint hypermobility, highly arched palate, enophthalmos and retrognathia.

Secondly, let’s talk about the most serious findings of Marfan Syndrome which are usually the cause of death in these patients:

Cardiovascular findings:

• Major criteria:

1. Aortic root dilatation.
2. Aortic dissections involving the ascending aorta.

• Minor criteria:

1. Mitral valve prolapse.
2. Dilatation of proximal main pulmonary artery.
3. Dilatation of descending aorta.

Ocular findings:

• The major criterion is dislocation of the lens caused by weakening of the suspensory ligament. Dislocation usually occurs in the superotemporal direction.
• Minor criteria include: myopia due to increased axial length of the globe. Flat cornea also may be present.

Dural findings (Dural Ectasia)

• Dural ectasia is a ballooning of the dural sac and the spinal canal, often associated with the nerve root sleeves out of the associated foramina. It usually occurs in the lumbosacral spine.
• The most common clinical symptoms are low back pain, headache, rectal pain and pain in the genital area. The symptoms are aggravated mainly in the supine position and are relieved by lying on the back.

Treatment

1. Back brace can help if scoliosis causes severe skeletal problems or pain.
2. Surgery for pectus excavatum or carinatum, to prevent skeletal complications and to relieve pain.
3. Annual eye exams become a must, as well as visits in between annual visits if any problems with eyesight are detected or suspected.

About The Author Ahmed Reda Abolmaaty

Hi, I'm Ahmed. I'm a medical student at Mansoura School of Medicine, Egypt. I love many fields of science, not just biology. I can help you understand anything in math, physics, and chemistry too xD I hope you like the articles I write here at Interactive Biology. If you have any questions, please don't hesitate to ask :)

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The kidneys are reddish-brown, bean-shaped organs situated retroperitoneal on the posterior abdominal wall. They extend from lumbar vertebra T12-L3. Normally the kidney is about the size of a mouse and measures approximately 11-12 cm in length, 5-6 cm in width and 2.5-3 cm in thickness.

The kidneys have a superior and inferior pole, medial and lateral margins, and an anterior and posterior surface. The superior pole of each kidney is deep to the rib cage. For the right kidney, its superior pole is at the 12th rib and for the left the superior pole is at ribs 11 and 12.

Anatomy of Kidney

On the medial margin of the kidney is concave region called the renal hilus. The renal hilum is the entrance to the renal sinus. Structures such as the renal veins, artery, nerves and lymphatic vessels are located in the renal hilum.

About The Author Sonya McKenzie

I am currently a "50% doctor." You might be wondering what that means. Well, I am currently in my last few weeks of my second year in medical school. I love anything to do with science and medicine. I have great interest in medicine from the preventive aspect.

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We have often heard the word immunity or resistivity of the body or general weakness of the body. What exactly do people mean when they say these words?

What is Immunity?

Virus In Blood

According to the modern definition, immunity is described as the ability of the body to recognize, neutralize, or destroy harmful foreign substances in our body. It is the same as the resistivity of the body.

In normal language, immunity can easily be termed as the defense system of our body. Our body needs specific optimal conditions for temperature, pH level, amount of water, food, etc to function properly. Also, a lot of foreign substances like bacteria, microorganisms, dust particles, and such enter our body while we breathe or eat or come in contact with infected materials. When some activity of these foreign substances threaten to disrupt the normal functioning of the body, the active defense factors of our body gets activated.

Types of Immunity

Immunity is classified in two types: Innate Immunity and Acquired immunity.

Innate Immunity

Innate immunity is also called Natural Immunity of the body. It is the inborn ability of the body to protect itself against pathogens and is transferred from mother to the baby. Since it doesn’t depend on previous exposure to microorganisms, it is also known as non-specific immunity. It is always available to protect the living body. The main strategy of innate immunity consists of various barriers that prevent their entry, or they immediately destroy any pathogens that enter our body.

Various Barriers of Natural Immunity

This natural immunity system of our body can be easily compared to an army of a country. Like a country has several defense systems in place e.g.: troops at the borders, troops sent out to war, spies, etc. , similarly our body too has multiple layers or barriers of defending itself from possible foreign invasions. These are:

Human Skin

Anatomical barriers

This is the outermost layer of defense. Periodic shredding of epidermis cells and mucous membranes form the anatomical barriers of the body. The microorganisms get trapped in the mucous membranes and are eventually eliminated from the body. Mucous membranes in the nose, as well as ear and skin are all a part of this barrier against germs.

Physiological barriers (exclusive body weather control)

Our body has the unique capability to control its physiological aspects like temperature, pH level and various bodily secretions which acts like a natural fence and sometimes weapons against the harmful substances. Some of these are always present (fence) and some are present in response to an infection (weapons).

One of the examples for the “fences” is acidity of gastric juice ( pH 1.2 to 3.0), which helps in digestion, as well as protection. Our stomach contains concentrated hydrochloric acid (0.5% of gastric juice) strong enough to dissolve any microorganism that comes in contact with it.

Child with Fever

Fever is a weapon of the body against an infection. Our body knows that high heat inhibits or stops the growth of various microorganisms. So what does it do?

You’re right. It goes ahead and torches them to retardation and death by raising the temperature of the bodily environment which is also commonly known as fever. It is one of the most common immunological responses of the body.

Another example is diarrhea where the body gathers all the water in your system with excess salts temporarily paralyzing the microorganisms, creating a kind of flood which flushes the harmful substances right out of your body.

Phagocytic barriers (Troops)

Like any well-equipped army, our body too contains soldiers in the form of leucocytes equipped with various enzymes which neutralize or destroy the foreign objects. These are also known as phagocytes. ‘Phago-’ comes from Greek Phagein which means ‘to ingest’ or ‘devour’. So, these awesome little soldiers go right ahead and actually eat the invading microorganisms. How cool is that?

The three basic types of phagocytes are macrophages (which will eat anything and ‘inform’ the others), neutrophils ( which either eat, poison, or lay traps for pathogens, and help others), and monocytes (which are capable of doing all of the above).

Inflammatory Barriers (special protection)

Inflammatory barriers provide protection to the body while wound healing. Through a wound or an ulcer, microorganisms get direct entry into the human body, and could forgo all the other immunological barriers. Thus, the body becomes more vulnerable to infections.

To prevent the entry of microorganisms, the body stations specialized soldier cells at the site of the wound to attack and destroy any pathogens that may enter through the wound or an ulcer.

Recommended to watch

To get a rough idea of what immunity is, you can watch the video below:

Click Here to Watch Ozzy and Drix

Ozzy is a monocyte and Drix is an antibody. Their main aim is to capture any criminals, i.e. pathogens in the city of (body of) Hector. Since it is sci-fi, some of the facts are pretty distorted, but you get the basic idea and it is extremely fun to watch.

About The Author Srushti Kumbhare

Hey everyone! I'm Srushti. I'm a science student. I love biology, knowing how things work inside things, that every system has various systems in it. Biology is full of wonder and it is one of my favorite hobbies. I really hope the articles are helpful. If you have any questions, I'll be happy to help. :)

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The neuron is, in my opinion, the coolest cell type with the most mind blowing structure you could find in any organism. Period.

The neuron’s main function is to transmit electrical signals (information) in one direction (dendrite to axon). The neuron is said to be polarized because information can only travel in a set direction (information cannot travel backwards).

External Structure of the Neuron

External Structure of a Neuron

First, let’s take a look at the external structure of the most abundant type of neuron in the human body: the multipolar neuron.

1. Cell Body

The cell body (a.k.a. the soma, in neuroscience jargon) contains the nucleus and other smaller internal structures. It is responsible for most of the protein and energy production of the cell.

It is generally circular (round) but can also have a more “triangular” shape such as in the pyramidal cell.

Each soma receives electrical impulses from a number of dendrites.

2. Dendrites

Dendrites are like antennas that receive information from other neurons and transmit that information to the soma. Each dendrite that connects to the soma contains many different “branches” and this ensemble is called the “dendritic tree.”

Let’s dive into a little more details here:

Each point where one segment of the dendrite branches into two segments is called a bifurcation. (The first time the dendrite branches in two is called the first bifurcation, the second time it branches in two is called the second bifurcation, and so on.)

The dendrites have the amazing ability to receive incoming signals directly on their membrane, or on tiny little protrusions called dendritic spines. My professor liked to say that these spines look like, “forests of tiny lollipops.”

3. The Axon

Each neuron has one axon that will transmit the information to the following cell. The axon connects to the soma at the axon hillock. The axon hillock is a very important structure as it is the final point where all the information from all the dendrites get integrated into one clear signal that will travel through the axon and to the next cell.

In a human body, axons will very often be covered by a myelin sheath that increases the speed of propagation of the electrical information. This myelin sheath has gaps, and these gaps are called Nodes of Ranvier.

Axons can branch as well, and each axonal branch is called an axon collateral.

The axon ends in small structures called synaptic terminals. The synaptic terminal will connect to another neuron’s dendrite (or dendritic spine) and transmit the information.

Now that we’ve mastered the basic external structure of a neuron, let’s look at the different types of neurons that we can find in the human body.

1. Multipolar neurons.

These neurons contain a number of dendrites and one axon. They are the most common type of neurons and they can be found more or less anywhere in the nervous system.
For example:

• Pyramidal neurons in the cerebral cortex
• Purkinje neurons in the cerebellum
• Motor neurons in the anterior horn of the spinal cord

2. Bipolar Neurons

Bipolar neurons have only two process that connect to the cell body: one dendrite and one axon. (This is easy to remember as, generally speaking, the prefix “bi” refers to the number two, such as in bilingual – two languages)

Bipolar neurons are only found in specific areas of the nervous system:

• In the retina
• In the nose (receptors of the olfactory epithelium)

3. Pseudounipolar neurons

There is only one process (this gives us the “unipolar part”) that branches into two (which is why we add “pseudo” at the beginning… It doesn’t look unipolar). This process is structurally similar to that of an axon, but it can receive information as well.

• Pseudounipolar neurons can be found in the spinal ganglions.

Minimum Points to remember:

Neurons are the coolest type of cells.  They are made of:

• A cell body-called the soma
• Dendrites that receive information
• An axon that transmits information to another cell.

Neurons are polarized in that the information can only travel in one direction: dendrite to axon.

There are 3 different types of neurons:

1. Multipolar neurons: one axon, many dendrites
2. Bipolar neurons: one axon, one dendrite
3. Pseudounipolar neurons: One process that branches in two.

That’s it for this introduction to the neuron’s structure.

If you want more articles and videos about the Nervous System, you can find them here. More resources are available to help make Biology fun. I invite you to absorb all the content you can find here at Interactive-Biology.com.

About The Author Mag Reves

Hi, I love to talk about, neuroanatomy, psychology, memory,... and pretty much anything related to the brain. I graduated from UCLA with a degree in Neuroscience and I also run another website dedicated to helping Pre-Meds become great medical school applicants.

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As cells get exposed to an injurious agent, these cells then try to adapt such that an injury would be prevented.
Watch and learn what these adaptations are in this video. More to come on the details of each.

Enjoy!

Transcript of Today’s Episode

Hello and welcome to another episode of Interactive Biology TV where we’re making Biology fun. My name is Leslie Samuel, and in this episode, I’m going to be talking about the four types of cellular adaptations.

Two videos ago, I answered the question, “What is a disease?” And, in the last episode, what I spoke about were the “Five Causes of Disease.” The first cause, the number one cause of disease was adaptation, and what I said was that an adaptation is a cellular reaction to prevent injury. So, there’s an injurious agent in the environment of the cell, and the cell reacts in a way to prevent injury.

You can go back and check out those videos, but in this video, what I want to talk about is the first cause of disease which is an adaptation. So, what we’re going to do is we’re going to talk about the four types of adaptations.

Adaptation number one is atrophy. Atrophy is when the cell decreases its functional part. The cell is basically reducing its size by decreasing its functional parts. That’s number one.

Number two is hypertrophy. That is when the individual cells increase in size, and that of course, is going to cause the tissue to increase in size.

Then, there’s hyperplasia. Hyperplasia is when we have more cells being formed. So, the cells are replicating, and as a result of that, the tissue is increasing in size.

With hypertrophy, we have the tissue increasing in size because the individual cells are increasing in size. In hyperplasia, we have the tissue increasing in size because we’re getting more cells, which make sense.

Then, the last type of adaptation will be metaplasia. And, that is when we have one tissue type that’s replaced by another tissue type. So, these are the four types of adaptations.

I’m going to go into more detail about those adaptations in later videos, but for this video, all I want you to be able to do is remember those four adaptations.

1.  Atrophy.
2. Hypertrophy.
3. Hyperplasia.
4. Metaplasia.

And, you can say it with me. Let’s say it together.

Number one is atrophy, hypertrophy, hyperplasia, and metaplasia. We can kind of say it together. We can almost dance to it. it’s that simple. So, atrophy, hypertrophy, hyperplasia, and metaplasia.

In the next video, we’re going to go into detail about atrophy, and we’re going to continue from there.

That’s it for this video.

If you want more videos like this, and more resources to help make Biology fun, I invite you to visit the website at Interactive-Biology.com.

That’s it for this video, and I’ll see you in the next one.

About The Author Leslie Samuel

Leslie Samuel is the creator of Interactive Biology. He created this site to help Make Biology Fun and has the goal of making this the biggest and best biology resource on the net.

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If disease is altered cell biology, what then are the factors that cause diseases? What are things that can change the cell’s condition? Watch and listen as Leslie discusses the five causes of diseases. Whatever the disease is, they will always be attributed to one of the five causes. Sounds simple, right?

Hope you have fun!

Transcript of Today’s Episode

Hello and welcome to another episode of Interactive Biology TV where we’re making Biology fun. My name is Leslie Samuel, and in this video, I’m going to be talking about the five causes of disease.

Last episode, Episode 70, we spoke about what a disease is, and if you watched that video, you’ll know that a disease at some level, is some kind of altered cell biology. So, what we’re talking about now is five causes of altered cell biology. If you need to revisit that episode, just head back over to Episode 70, and you’ll learn about that.

What are the five causes of disease?

Cause number one is adaptation. What we’re saying here is that there’s some kind of an injurious agent that comes into the environment of a cell, and the cell tries to adapt to that agent, and that can cause altered cell biology.

Number one is adaptation. Number two is injury. There is an injurious agent the cell tries to adapt, and it does certain things to try to adapt, and at a certain point, it can no longer adapt, and the cell becomes injured.

Cause number one, adaptation. Cause number two, injury. And, then, if we go one step beyond that, there’s cellular death. So, the cell tries to adapt, it gets injured, and if that injurious agent stays around for long enough, that can cause the cells to die.

So, cause number one, we have adaptation. Cause number two, we have injury. And, cause number three, cellular death. And then, there’s a fourth cause, and this is called neoplasia. And, what this is is when there’s something that causes the cell to uncontrollably divide. In other words, we’re talking here about cancer. So, the fourth cause of altered cell biology is neoplasia.

And then, the last cause, cause number five is aging. The cells get older, and as they get older, certain things happen that cause the cell’s biology to be altered.

So, there we have it, the five causes. Cause number one is, adaptation. Cause number two is injury. Cause number three is cellular death. Cause number four is neoplasia. And, cause number five is aging.

I don’t care what disease you’re talking about, but we can fit all of them into one or more of these five causes.

That’s it for this video. My name is Leslie Samuel from Interactive-biology.com. I want to invite you to go back to the website, and check out other videos that we have, and other resources to help make Biology fun.

That’s it for this video, and I’ll see you on the next one.

About The Author Leslie Samuel

Leslie Samuel is the creator of Interactive Biology. He created this site to help Make Biology Fun and has the goal of making this the biggest and best biology resource on the net.

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This is the first in Leslie’s joke series. Something for your amusement and pleasure. It’s time to get some time off from all the books and give yourself a little laughter.

Listen to the story of the intelligent professor as he collects his observation about his frog experiment. Would you have thought about it this way too?

About The Author Leslie Samuel

Leslie Samuel is the creator of Interactive Biology. He created this site to help Make Biology Fun and has the goal of making this the biggest and best biology resource on the net.

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As promised, here is the start of a set of new videos to be uploaded to the site. Let’s start off this year by learning what a disease is from a Biological perspective.

Also, you’ll notice something new with the video format. Let me know what you think.

Have fun!

Transcript of Today’s Episode

Hello and welcome to another episode of Interactive Biology TV where we’re making Biology fun. My name is Leslie Samuel and in this episode, Episode 070, I’m going to be answering a simple question, What is a disease? I know what you’re thinking. Everybody knows what a disease is. But, since this Interactive Biology, we’re going to look at it from a Biological perspective. So, let’s get right into it.

A disease is an abnormal condition that affects the body of an organism.

What’s an organism? An organism is a living thing. And, when we’re talking about Pathology, or Pathophysiology, we’re talking about human beings. So, we’re talking about an abnormal condition that affects the body of a human being. A disease is usually associated with a number of symptoms or signs. But, what does these all really means?

Okay, so we have an abnormal condition affecting the body. But, what is the body? I know what you’re thinking, the body of a human being is made up of systems. So, we have the circulatory system, we have the muscular system, the skeletal system, the urinary system, all of these different systems that come together to form a human being.

But, what are these systems? I know what you’re thinking now. You’re thinking these systems are made up of organs, and you’re right! For example, the circulatory system is made of the heart, and the blood vessels and all these things come together to form the circulatory system.

But, what is an organ? I know what you’re thinking because you’re smart. An organ is made up of tissues. All right, so we have it down to the tissue level. But, what is a tissue? Finally, you’re there. A tissue is made up of cells. All living things — human, or dog, or cat, or wolf, whatever it is, all living things are made up of cells.

So, if you have an abnormal condition that affects an organism, that’s because we have something that’s affecting one or more of the organ systems. And then, of course, it’s affecting one or more of the organs, one or more of the tissues, and one or more of the different cell types. So, in essence, what we’re saying is, if we have a disease, we have an abnormal cellular structure, and/or function, there is something wrong at the cellular level that’s causing this thing to be manifested on the level of the organism.

Now, there are many different types of diseases. But, I’m going to tell you something that’s going to make it much more simple. All of these disease can be attributed to one of five causes. Doesn’t that sound simple? If we know these five causes, we could explain to some level every single disease that’s out there.

What are those five causes? That’s what we’re going to talk about in the next episode.

That’s all for this episode. Once again, I want to invite you to come back to the website at Interactive-biology.com, where you’re going to find more videos just like this, and many other resources to help you make Biology fun.

By the way, what do you think about this new video format? Let me know in the comments below. That’s it for now, and I’ll see you in the next video.

About The Author Leslie Samuel

Leslie Samuel is the creator of Interactive Biology. He created this site to help Make Biology Fun and has the goal of making this the biggest and best biology resource on the net.

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Interactive Biology by Leslie Samuel is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.

Donations

If you appreciate what we do here at Interactive Biology, listen to Leo and Consider donating

About The Author Leslie Samuel

Leslie Samuel is the creator of Interactive Biology. He created this site to help Make Biology Fun and has the goal of making this the biggest and best biology resource on the net.

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The central nervous system is such a delicate part of our body that it needs a stable protection against damage and injuries. Learn what protects and surrounds it from the pressures outside of the body.

Enjoy!

Transcript of Today’s Episode

Hello and welcome to another episode of Interactive-Biology TV where we’re making Biology fun. My name is Leslie Samuel, and in this episode, Episode 069, I’m going to be talking about the meninges of the Central Nervous System. So, let’s get right into it.

Now, the central nervous system is very delicate and needs to be protected. Speaking about delicate central nervous systems, over here to the right we have an interesting picture. This picture basically shows archaeological remains of patients of brain surgery, and they were performed by the ancient doctors of the Incan empire back in the 15th century. You can see we have some significant holes here.

In studying these archaeological remains, we are able to see that significant advances were made to where the success rate of the doctors and the surgeons that performed these surgeries was up to 90 percent. So, there’s a lot going on there, but that’s not the topic for this episode. We’re going to talk more about the meninges as opposed to the archaeological stuff.

Part of the protection is provided by the meninges. We need to protect the brain, we need to protect the spinal cord, and part of that protection is done by the meninges.

The meninges surround the central nervous system, so they go around the central nervous system, and they suspend it in a protective jacket. That protective jacket is filled with CSF. That stands for ‘cerebrospinal fluid.’

Let’s kind of try to visualize this. Here we have a picture. This is showing the brain. This part here is the brain, so this is dealing with the cortex. As you can see, we have a number of layers even before we get to the bone.

The first layer is called the, ‘pia mater,’ and then, we have the ‘arachnoid layer,’ and ‘dura mater.’ So, pia mater, arachnoid, and dura mater. A good way of remembering this from inside to out is, you have a P.A.D. that surrounds your brain: ‘P’ for pia mater; ‘A’ for arachnoid, and ‘D’ for the dura mater. And then, of course, we have the bone, the periosteum, which is the membrane that surrounds the bone, and then, we have the skin.

The three meninges– pia mater, arachnoid, and dura mater, and you can also see that over here. Here, we’re looking at the brain. So, this is the cerebrum. You can see, we have this very thin layer that’s directly connected to the brain. That is the pia mater, then, we have a space. This is called , the ‘subarachnoid space,’ but, we’re not going to go into that in this video.

Then, we have this green line that goes around here, and that thin line is the arachnoid. And then, we have a thicker band, and that is the dura mater. That’s the wider part here. So, those are the three layers, .A.D.

Let’s look at a different picture that shows the same thing here. We have this red line as the pia mater. And then, we have this space, then, we have this thin line here. That is the arachnoid, and we have the dura mater. Pia, arachnoid, and the dura.

As you can see, the dura is the thickest, then we have the arachnoid, and then, the very thin pia mater.

All right, so, if you want to look at an organizational chart, here we have the meninges, and the three types are the dura mater, arachnoid mater, and pia mater—those are the three meninges. And then, we can take the dura mater and subdivide that into the meningeal layer and the peritoneal layer.

The peritoneal layer is the layer that is attached to the bone. So, the dura mater has two layers: The meningeal layer and the peritoneal layer.

The arachnoid and pia mater, those are thin layers that we can put together and call leptomeninges. “Lepto” comes from the Greek word that means “thin or fine,” and “dura ” means tough. And, that’s why you get words like , “Durable.” Something that’s durable is very tough. The dura mater is tougher, and it’s stronger and thicker, and then, we have the two thin layers called the arachnoid and pia mater. Both of them, we can take them together and call them, ‘leptomeninges.’

That’s all I want to talk about in this video. As usual, I want to invite you to visit the website, Interactive-Biology.com for more Biology videos, other resources… We just released a new Interactive study Guide, and you can check that out. You can get all the resources at the site, to help make Biology fun.

This is Leslie Samuel. That’s it for this video, and I’ll see you in the next one.

About The Author Leslie Samuel

Leslie Samuel is the creator of Interactive Biology. He created this site to help Make Biology Fun and has the goal of making this the biggest and best biology resource on the net.

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In this episode, Leslie talks about our “little brain,” or our cerebellum — about its different parts and functions of each. The cerebellum has three fiber peduncles attaching it to the brain stem, and also has three lobes just like our brain. Learn more about the functions and locations of each as you watch through this episode.

Enjoy!

Also, check out the following video about a boy that was born without a Cerebellum. It will give you a better understanding of what the Cerebellum does.

Transcript of Today’s Episode

Hello and welcome to another episode of Interactive-Biology TV where we’re making Biology fun. My name is Leslie Samuel, and in this episode, Episode 068, I’m going to be talking about the anatomy and functions of the cerebellum. So, let’s get right into it.

Here, we’re looking at a picture of the cerebellum. The cerebellum would be this part here, then, of course, we have the brain stem that is just anterior to the cerebellum. Of course, superior to that we have the cerebrum. This is just looking at a section of the brain, the section showing the cerebellum. Just to let you know, if you want to revisit what I’ve already said about the cerebellum, you can go to Episode 026. In Episode 026, I talk about the functions of the cerebellum, and I go into a little bit of detail.

What we’re going to do is we’re going to build on what we spoke about in that episode and talk a little more about the anatomy and the functions of the cerebellum.

Just to recap, “cerebellum” is Latin for “little brain.” It looks like a little brain at the back and the bottom of the brain. So, posterior and inferior, that would be where the cerebellum is located. The functions of the cerebellum, of course, we’re dealing with integration, regulation, and coordination of motion.

You want to move from one location to the next, you want to move your arm, you want to move some part of your body, the cerebellum is very much involved in integrating the signals or regulating what’s going on and coordinating that motion. That is the cerebellum and what it does.

Here’s a different picture of the cerebellum. You can see, we have the cerebellum here. It’s a drawing of the cerebellum from Gray’s Anatomy. Here you can see we have the brain stem. Of course, at the top, we’re going to have the midbrain, and then the pons, and the medulla.

What I want to emphasize here is that we have three pairs of fiber bundles that are attaching the cerebellum to the brain stem. Those fibers are called the cerebellar peduncles. We have three pairs of them. You can see here, we have the superior peduncle. (This is pointing out one of the superior peduncles). Then, we have, of course, the middle peduncles (so, that would be those fibers here). And then, we have the inferior peduncles which would be, of course, beneath the middle peduncles. You can see one here, and one over here.

We have these three pairs of peduncles, the superior peduncles, middle peduncles, and the inferior peduncles. Those connect that cerebellum to the brain stem. Of course, they’re going to connect to different regions. The superior peduncles are going to connect to the upper pons, (so, here we have the pons, and that’s connecting to the upper pons). The middle peduncles are going to connect it to the lateral aspect of the pons, (that’s right here). And then, the inferior peduncles, it’s going to connect to the dorsal lateral surface of the upper medulla. So, here we have the medulla, dorsal, that would be kind of to the back here; and lateral, so, we’re dealing with the upper medulla in this area. That’s where the inferior peduncles connect. We have all these fibers that are connecting the cerebellum to the brain stem.

Let’s move on from there and take at another look at the cerebellum. What we’re doing here, in these pictures, these are pictures of a cerebellum from a human, but in the top picture, we are looking at the posterior view, so from the back of the head, here, we are looking at the anterior view. This is the side of the brain stem. The brain stem would normally be in the front here. So, posterior and anterior.

What I want to show you is that we have three lobes in the cerebellum. Just like the brain has lobes, cerebellum is a little brain. It also has its lobes. Those three lobes are the anterior lobe, which of course, would be the one that you’re seeing here. So, these would be the two anterior lobes. Then, if you look from the back, you get the posterior lobe, so you can see this is one posterior lobe, and this is another posterior lobe.

Then, we have the flocculonodular lobe. That would be inferior, but it’s kind of small, so you can’t see it, as well, (it’s not shown in this picture). It’s kind of blocked by the posterior lobe. So, we have the anterior lobe, posterior lobe, and the flocculonodular lobe. Those are the three lobes.

The largest lobe would be, you can see that here, the posterior lobes. You can see that’s bigger than the anterior. The smallest would be the flocculonodular lobe.

There’s one more structure that I want to talk about. That is called the vermis. You can see the vermis right there, kind of in between the two lobes.

The cerebellum is involved in integrating, regulating, and coordinating motion. It needs to get input from the regions of the brain that are responsible and that are involved in that process. It needs to get information from the different parts of the central nervous system. These three lobes are going to get information from different parts. And, the anterior lobe gets information from the spinal cord. So, you have these peripheral nerves coming into the spinal cord giving information about what’s going on in the periphery of your body, what’s going on with your hands, and your legs, your extremities. It’s going to take that information, of course, and integrate that with some other information that the cerebellum is getting.

The posterior lobe is going to get information from the cortex. We’ve spoken about areas in the cortex. We’ve spoken about areas in the cortex that are responsible and that are involved in the process of movement.

And, lastly, the flocculonodular lobe is going to get information from the vestibuli. That’s in the inner ear. The vestibuli are heavily involved in proprioception being aware of where your body is.

So, anterior lobe getting information from the spinal cord; the posterior lobe getting information from the cortex; the flocculonodular lobe getting information from the vestibuli. The cerebellum is taking all that information, processing it, and helping you to have coordinated motion.

I hope that makes sense. That’s pretty much all I want to cover in this episode. As usual, I want to invite you to visit the website at www.Interactive-Biology.com. You’re going to get more Biology videos there, more resources to help make Biology fun, transcripts of these videos and just a bunch of other stuff. So, head on over there, www.Interactive-Biology.com.

This is Leslie Samuel. That’s it for this video, and I’ll see you on the next one.

About The Author Leslie Samuel

Leslie Samuel is the creator of Interactive Biology. He created this site to help Make Biology Fun and has the goal of making this the biggest and best biology resource on the net.

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Leslie is on a roll today! In this next episode, he tackles about the parts and functions of the occipital and temporal lobes: the occipital lobe being the primary visual cortex and the temporal lobe being involved in processing auditory signals. Watch to learn more about these parts of the brain and their functions, as well.

Have fun!

Transcript of Today’s Episode

Hello and welcome to another of episode of Interactive-Biology TV where we’re making Biology fun. My name is Leslie Samuel, and in this episode, Episode 067, I’m going to be talking about the anatomy and functions of the occipital and temporal Lobes. Let’s get right into it.

The occipital lobe, you can see it here, to the posterior end of the brain, and it’s here in pink. You just see a small surface here, but I do want to emphasize that it also extends medially. It’s more prominent as you go medially into the brain. We’re going to see that in the next slide.

This is the primary visual cortex. When you see something, light is coming into the eyes. It’s hitting the rods and the cones in the retina, and there are some signals being sent to the brain. Those signals that are sent to the brain are coming to the visual cortex in the occipital lobe, and then, there’s processing that’s happening there.

If you want to review how that happens in the eyes, you can check out Episode 034 and 035 where we deal with some of those things in terms of how the rods and the cones process the information, and then, how they are sent to the brain. This is the region in the brain that they’re coming so that they can be processed, and so that you can see this screen and you can see all of the things that you see.

Let’s look at a mid-sagittal section, so that we can see the medial aspect of the brain, and you can see here (let’s do it in blue), you can see in this area, we have the occipital lobe. You are just seeing the outside surface and it does extend more medially. You can see that here.

Okay, so let’s move on now to the temporal lobe. The temporal lobe, you can see, is over here. It’s kind of to the side of the brain, and it’s in green. And, the temporal lobe is involved in processing auditory signals.

We’ve spoken about how hearing happens. You can look from Episode 036 through 040. I covered hearing there. Specifically, in Episode 040, I spoke about the hair cells, and about how when you hear something, there are vibrations that are happening. That causes the hair cells to bend, and when they bend, they send signals to the brain. This is the region we’re talking about in the brain.

Now, specifically, there’s a region that’s not shown, the Gyri of Heschl, and that is found in the most superior inner aspect of the temporal lobe. As we go more medial, you will see, we have some gyri, and we call those Gyri of Heschl, and that is where we find the primary auditory receiving area. This is where the signals are coming from the hair cells, so that we can hear stuff.

All right. Let’s go a little further into the temporal lobe. We’re going to look at the three regions. We have the superior temporal gyrus, the middle temporal gyrus, and the inferior temporal gyrus. Those are the three sections. And you can see they’re separated by these two sulci.

When I look at something that’s moving, there’s some processing that needs to happen for me to understand that that object is moving. And there are regions in the middle and inferior Gyri that are involved in perceiving moving objects, and also recognizing faces. So, you’re getting now into some more detailed processing so that you can see someone and recognize who they are by looking at their face. You can understand that objects are moving because of the processing that’s happening in these areas.

That’s pretty much all I want to say about that for now. As usual, you can visit the website at www.Interactive-Biology.com, and there you can find more Biology videos. You can find transcripts of all the videos so you can print them out and read them. You can find all kinds of resources to help make Biology fun.

This is Leslie Samuel. That’s it for now, and I’ll see you in the next one.

About The Author Leslie Samuel

Leslie Samuel is the creator of Interactive Biology. He created this site to help Make Biology Fun and has the goal of making this the biggest and best biology resource on the net.

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Today, Leslie discusses the parts and functions of the parietal lobe. Among it’s parts, Wernicke’s area is said to help us understand spoken language. The parietal lobe is also involved in other processes such as perceiving and processing somatosensory events. Watch the video to learn more in detail as Leslie talks about the anatomy and functions of this part of the brain.

Transcript of Today’s Episode

Hello and welcome to another episode of Interactive-Biology TV where we’re making Biology fun! My name is Leslie Samuel and in this episode, Episode 066, I am going to be talking about the anatomy and functions of the parietal lobe. So, let’s get right into it.

The parietal lobe, as you can see here, is this region right here. We’re starting at the central sulcus, it goes down, and on the inferior end over here, we have the lateral cerebral fissure, and posteriorly, we have the parietal occipital fissure that separates the parietal lobe from the occipital lobe.

The parietal lobe is primarily involved in perceiving and processing somatosensory events. We’re talking about things like touch, and temperature, and body position, and pain. The term that we use for body position is proprioception, and the term that we use for pain is nociception. So, proprioception and nociception, those are also involved in the processing of the parietal lobe. Let’s go a little more into that.

Here we have, on the most anterior end, we have the postcentral gyrus. Of course, the postcentral gyrus is going to be just posterior to the central sulcus. And then, we have the postcentral sulcus on the posterior end of that gyrus. The function of that gyrus is basically receiving somesthetic information. We’re talking about kinesthetic and tactile information. “Kinesthetic,” meaning body movements and “tactile” would be touch. That information comes in and it goes to the postcentral gyrus. There’s some processing that happens there for us to be able to recognize movements of body, and when we get touched we can feel that because of some of the processing that’s happening right here.

Of course, the left half of the brain, so the left postcentral gyrus is going to be getting information from the right side of the body, and the right postcentral gyrus is going to be receiving information from the left side of the body. Not only that, but it’s also what we call somatotopically organized. What that means is specific parts of the postcentral gyrus are going to receive information from specific parts of the body.

For example, if we are looking at the face and head, the information that’s coming from the face and the head are going to be processed in the most inferior parts of the postcentral gyrus. As we go more superior, we’re going to be starting to get input from the upper limbs. If we go more medial, we’re going more towards the center of the brain, we’re going to be getting information from the lower limbs.

So, it’s somatotopically organized, specific parts of this gyrus gets information from specific parts of the body. We’re going to see that a lot in the different parts of the brain. So, postcentral gyrus, we spoke about that.

Then, we have the superior parietal lobule, and of course, that’s going to be superior. What that does is it integrates sensory and motor functions. Then, we have the inferior parietal lobule. You can see that the superior and inferior parietal lobules are separated by this intraparietal sulcus. “Intraparietal,” “intra” means it’s inside, or in between. “Parietal,” the parietal lobe. That’s the intraparietal sulcus.

In the inferior parietal lobule, you see here we have the supramarginal gyrus and the angular gyrus. These two gyri receive input from the auditory and visual cortices, and of course, it’s processing auditory information and visual information. In order for us to see and hear, we’re getting information through this supramarginal gyrus and the angular gyrus.

Then, we have a specialized area that’s called Wernicke’s area. I know it looks different than I’m pronouncing it, but that’s the German pronunciation. What that helps us do is understand spoken language. So, someone is speaking to you, and you need to understand what they are saying. There’s processing that’s happening in the Wernicke’s area. Of course, in some cases, it’s more difficult to understand some people than others. (I’m sorry I shouldn’t have done that).

Okay, let’s continue. If there’s damage to this area, so if we have like lesions in the Wernicke’s area, that can result in Wernicke’s aphasia. What that is, is impairment of comprehension and repetition. You have a hard time understanding spoken language because of the damage in this area.

That’s pretty much it. That’s all I want to cover for this episode. As usual, I want to invite you to visit the website at www.Interactive-Biology.com for more Biology videos. You can also get the transcripts of every video that I have posted here, all of the Interactive-Biology TV videos, and a bunch of other resources to help make Biology fun.

That’s pretty much it for now, and I’ll see you on the next one.

About The Author Leslie Samuel

Leslie Samuel is the creator of Interactive Biology. He created this site to help Make Biology Fun and has the goal of making this the biggest and best biology resource on the net.

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Learn more about the brain gyri and sulci or fissures. Get familiar with the anatomy and functions of the frontal lobe in this easy to understand video. Leslie has also included an interesting video about an individual with Broca’s aphasia, a defect in the Broca’s Motor Speech area resulting in speech problems.

Have fun learning!

Transcript of Today’s Episode

Hello and welcome to another episode of Interactive-Biology TV where we’re making Biology fun! My name is Leslie Samuel and in this episode, Episode 065, I’m going to be talking about the anatomy and functions of the frontal lobe. But, before I talk about that, let’s talk about the folds in the cerebrum.

Now, when we’re talking about ‘gyri,’ we’re talking about the folds. You can see here in this brain, we have all these little folds that go all throughout the brain. Those are called ‘gyri.’ If you’re dealing with one of them, you’re not going to say gyri, but you’re going to say ‘gyrus.’

Then, we have the ‘sulci’ or the ‘fissures.’ Sometimes, we use these interchangeably, but these are the depressions in the brain that define the lobar boundaries. Here, we have the different lobes, and you can see we have all of these depressions, in other words, we have all of these grooves that are going throughout the different lobes of the brain. Those are called, ‘sulci,’ and in some cases, we call them, fissures.

So, with that understanding, let’s look at the frontal lobe in the brain. Now, the frontal lobe, we have two major boundaries that define the frontal lobe. Over here, we have the central sulcus. You can see that’s going through here. That is the posterior aspect (okay, so that’s towards the back). The posterior aspect of the frontal lobe, the boundary is the central sulcus.

Then, if we go inferiorly here, we have the lateral sulcus, or we can call it the Sylvian sulcus. That’s this boundary here on the inferior end of the frontal lobe. The central sulcus, posteriorly, and the Sylvian or lateral sulcus, inferiorly. And, this here would be the frontal lobe.

The first thing I want to talk about is this section here that’s called the precentral gyrus. Here, you can see in this case, it’s called the anterior central gyrus, but this is the precentral gyrus. The function of that region is it serves as the primary motor cortex. So, it’s basically getting motor signals from different parts of the brain, and it’s integrating it in this region. The precentral gyrus. This is where a lot of that motor function is integrated.

Just anterior to that, it’s not shown in this image, but I’m just going to kind of draw a section in here coming from the, from this part all the way. Maybe it’s not that right. It’s kind of, it’s not exact, but this is the pre-motor cortex, which makes sense. If this is the primary motor cortex, and this is, right before that, it’s the pre-motor cortex. Here, we have kind of an area that we call the ‘supplemental motor area.’ So, it’s the supplemental motor area. That plays a big role in initiating movements. You want to move, there’s an initiation that has to happen, and this has something to do with that process of initiating movements.

Now, as I said before, the boundaries aren’t necessarily definitely defined. I can’t see that it goes from right here to right there. But, in this area here, let’s show this area. I’ll just color it in a little bit. We have what’s called the ‘frontal eye fields.’ (Let me write that out—frontal eye fields). And, that is involved in the movement of the eyes, but a specific movement. When I look to the left and I look to the right, my eyes are moving horizontally. The frontal eye fields are involved in the horizontal movement of the eye.

Let’s move on. Then, we have, if we go anterior from that area, we have the superior frontal gyrus, the middle frontal gyrus, and the inferior frontal gyrus. So, superior, middle, and inferior frontal gyrus.

And, in the left hemisphere of the brain in the frontal lobe, we have an area that we call the Broca’s motor speech area. That has a big part to do with the motor components of speech. So, you’re speaking, I am speaking into this microphone right now, my mouth is moving in certain ways, and there are muscles that are controlling that, and this Broca’s motor speech area is very much involved in that process. Once again, it’s in the left hemisphere, not the right, and that deals with motor control of speech.

Now, if there’s damage to this area. If something happens, and that causes this area to be damaged, the result of that can be what we call, ‘Broca’s aphasia.’ When you have that condition, it causes a form of language impairment where you cannot speak well. It’s not that you can’t comprehend, but the motor control of that speech doesn’t function as well because the Broca’s motor speech area is damaged.

I have a little video here to show an example of that. So, let’s go ahead and take a look at that right now. (Video starts to play).

So, this is an example of Broca’s aphasia. You can see he had some problems speaking. Not necessarily in comprehension, but in just the motor control in forming the words and putting together long strings of the words to make complete sentences. That is an example of Broca’s aphasia.

If we look all the way into the anterior section, you’ll see that we have the prefrontal cortex and that plays a very important role in the process of intellectual functioning, and emotional responses, and so on. So, intellectual and emotional events that has a lot to do with what happens in the prefrontal cortex.

There’s another area that we cannot see in this picture, and in order to see it, we need to remove a section from here because it’s deeper in, it’s more medial. We’re going to do that now, and take a look at that. Here, you can see we have removed the part of the temporal lobe and part of the frontal lobe and then, here, there’s an area that we call the ‘insula.’ You can see it over here, and you can also see right here. This is the insular cortex. This picture over here is a coronal section of the brain. We just take a section of the brain right in this area, and you can see the insula right here.

Depending on what book you read, you might get different explanations as to the function of the insula, anything from taste, sensation, to emotions, to thoughts, pain sensations, visual sensations in terms of, you know, feeling hungry and thirsty. That’s attributed to that region. We’re not 100% clear on how this works, but we do have some suggestions as to its function.

The last thing I want to talk about is what we see right here. This structure is called the corpus callosum. That is responsible for connecting the two hemispheres, and you can see as the cortex goes medially, it borders in the inferior aspect with that corpus callosum. We can see it even clearer here. We can see the corpus callosum. You can see it starts here in the frontal cortex, and it goes back here. So, this is the corpus callosum. If we’re dealing with the frontal cortex, that does border with the corpus callosum inferiorly. That is shown very well right there.

That’s pretty much all I want to cover for this episode. As usual, you can visit the website at Interactive-Biology.com for more Biology videos. You could find transcripts of all the videos and a number of other resources to help make Biology fun.

This is Leslie Samuel. That’s it for now, and I’ll see you in the next one.

About The Author Leslie Samuel

Leslie Samuel is the creator of Interactive Biology. He created this site to help Make Biology Fun and has the goal of making this the biggest and best biology resource on the net.

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http://www.youtube.com/watch?v=vhBRo1cMocA

Here’s another whole new episode to make anatomy easier for everyone. Learn about the different anatomical planes with Leslie as he goes through each one including the spatial relationships between parts in the human body. This will be a great help when you go deeper into anatomy and neuroanatomy making it easier for everyone to understand and learn new concepts.

Enjoy!

Transcript of Today’s Episode

Hello and welcome to another episode of Interactive-Biology TV where we’re making Biology fun! My name is Leslie Samuel. In this episode, Episode 064, I’m going to be talking about the anatomical planes and spatial relationships in the human body. As we go into neuroanatomy, we’re going to need to know these planes and these spatial relationships. Let’s get right into it.

Here we have the human body. I want to talk about the three different types of planes that we have. First, we have the coronal or the frontal plane. That’s a vertical plane at a right angle to the cerebral axis. You can see that plane here.

If you got a right angle to that, of course, we have the sagittal plane, which is a vertical plane, but it is parallel to the cerebral axis. You can see that plane over here.

We have a mid-sagittal plane, which means it goes through the midline. You can see that plane over here in red, and then, we have a parasagittal plane, which is just off the midline. So, for example, a parasagittal plane would go through, instead of the midline, let’s say, it goes through right about here. And, that continues down just like the mid-sagittal plane. But, instead of going through the midline, it’s just off the midline. That’s parasagittal.

Then, we have the horizontal plane or the transverse plane, which is parallel to the floor.

Let’s look at some location terms in terms of spatial relationships between two parts of the body.
If we’re talking about something that’s ‘superior,’ that means it’s above another part. If it’s ‘inferior,’ which would be the exact opposite, that means it’s below another part. And then, we have terms like ‘rostral,’ which means towards the head. And, this is when we’re looking at general anatomy assuming that we’re talking about beneath the brain, beneath the head. ‘Rostral’ is towards the head, and ‘caudal’ would be toward the tail or the coccyx. In other words it’s the opposite of rostral.

And then, we have ‘anterior,’ that’s towards the front, or ventral, is also towards the front. And then, we have posterior or dorsal, and that’s towards the back. Anterior and posterior are opposite. Dorsal and ventral are opposite terms also.

We have a few more to go over. That would be ‘medial,’ which is towards the midline; ‘lateral,’ which is farther away from the midline as you can see here. We have ‘proximal,’ which is nearest to the point of origin so, it’s closer to something; and ‘distal’ means farther from the point of origin. So, it’s farther away from whatever that point of origin is. That’s not illustrated in the picture over here, but I’m sure you get the point.

Then, we have ‘ipsilateral,’ which is on the same side of the body. Opposite of that would be ‘contralateral,’ which is on the opposite side of the body. For example, if we are looking at the right leg, the ipsilateral arm would be the right arm. The contralateral arm, of course, would be the left arm. So, ipsilateral means it’s on the same side. Contralateral means it’s on the opposite side of the body.

The interesting thing about these directions is what happens when the spinal cord enters the cranium and we get the brain. Because beneath the brain or beneath the head, we said that rostral was towards the head, and caudal was away from the head; ventral or anterior is the front of the body; dorsal or posterior is towards the back of the body.

When we get into the brain, and we pass the midbrain region, which is this region over here, what happens is that there’s a hundred, approximately a hundred-degree bend. So, in other words, it comes and it bends in that direction. What we have then, is dorsal being the top of the brain, and ventral being towards the bottom of the brain; rostral being towards the front, rostral or anterior; caudal being towards the back, or posterior being towards the back of the brain. You can see we have this shift. Instead of dorsal and ventral being towards the back and towards the front. When we’re beneath the brain, as we pass the midbrain region, dorsal now shifts to the top of the brain, and ventral towards the bottom of the brain. So, the ventral surface of the brain would be this surface here. The dorsal surface of the brain would be towards this surface. Caudal surface or the posterior surface of the brain would be this end. And, the rostral or the anterior surface of the brain would be towards this part here.

Another way of looking at this is by looking at these little diagrams over here where we have rostral, caudal, ventral, and dorsal, but when we get above the brain, it’s a little different. It shifts. Rostral is no longer going towards the top, but now, that’s going towards the front. Caudal towards the back. Dorsal towards the top, and ventral towards the bottom of the brain.

However, when it comes to superior and inferior, that stays the same. Superior means towards the top of the brain. Inferior means towards the tail or coccyx, in other words, going towards the bottom. Anterior is always front, and posterior is behind.

This is going to be important when we go into specific details inside the brain and the spatial relationships between the different parts.

That’s pretty much all for now. As usual, I want to invite you to visit www.Interactive-Biology.com, that’s the website where you can find more of these Biology videos, other resources, and a bunch of stuff to help make Biology fun.

This is Leslie Samuel. That’s it for this video, and I’ll see you in the next one.

About The Author Leslie Samuel

Leslie Samuel is the creator of Interactive Biology. He created this site to help Make Biology Fun and has the goal of making this the biggest and best biology resource on the net.

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http://www.youtube.com/watch?v=dOYOdJG0E0s

Join Leslie as he gives you a review of the brain and it’s different major divisions.

Enjoy!

Transcript of Today’s Episode

Hello and welcome to another episode of Interactive-Biology TV, where we’re making Biology fun! My name is Leslie Samuel and in this episode, Episode 063, we’re going to take a step back, and we’re going to talk about the divisions of the Nervous System. Let’s get right into it.

If you go all the way back to Episode 001, we spoke about the Nervous System. We said that the nervous system is basically the ‘control center’ of the body.

What we’re going to do is we’re going to take this, and we’re going to look at the divisions within the nervous system. First, we have the Central Nervous System, and we have the Peripheral Nervous System. These are the two systems that we can divide the nervous system into.

The Central Nervous System, that is the processing center of the nervous system. A lot of processing happens here. The Peripheral Nervous System is what connects the Central Nervous System to the limbs and the organs. So, we have the processing in the central, and then, we have the Peripheral Nervous System. These work together very well.

Now, let’s take the Central Nervous System and divide that. That can be divided into the brain and the spinal cord. The brain, that’s center of the nervous system. This is where most of the processing are happening. This is the part that’s found within the skull. This is where things like thought, and emotion, coordinating the body’s activities, all of that stuff happens in the brain.

Then, of course, we have the spinal cord. The spinal cord sends signal to and from the brain, to and from the rest of the body. So, it’s connecting the brain to the rest of the body, basically. Sensory signals come in to the spinal cord, and motor signals go out from the spinal cord. We’re going to talk about those as we deal with the peripheral nervous system. Let’s head on over there right now.

The peripheral nervous, once again, consists of two parts: that’s the Somatic Nervous System and the Autonomic Nervous System.

Let’s talk about the ‘somatic’ first. The Somatic Nervous System is where we’re going to get control of voluntary activities. This is where skeletal muscles are involved. If, for example, I want to walk. I need to contract the muscles in my legs. That is voluntary activity that is controlled by the somatic nervous system. If I want to smile and you can control the muscles in my face. By the way, it takes less muscles to smile than to frown. But, I’m sure you know that. This is all in the Somatic Nervous System.

And, then of course, we have the Autonomic Nervous System which is not voluntary. This is the involuntary things that happen in the body. So, it controls visual functions like heart rate, respiration rate, digestion, those things you don’t need to think about. They just happen. They are “involuntary,” and that is under the control of the Autonomic Nervous System.

We can take the Autonomic Nervous System, and of course, we’re going to divide that into two parts. We have the Sympathetic Nervous System and the Parasympathetic Nervous System.

The Sympathetic Nervous System, that is involved in the ‘flight or fight response.’ It’s what happens to your body when your body is under stress. Things like increasing your heart rate and respiration rate… Anything that you’re increasing. This is usually under the control of the sympathetic nervous system. So, if you go for a nice long jog, and you’re heart rate starts increasing and your respiration rate increases, that is under the control of your sympathetic nervous system.

Then, of course, we have the parasympathetic, which is opposite to the sympathetic. This is involved during rest and digest activities. It’s the opposite of under stress. It’s when there is rest. You’re slowing things down. You’re relaxing. That is more parasympathetic. These are both under the autonomic nervous system.

So, there we have it. Those are the divisions of the nervous system. I hope that was clear to you. That’s pretty much all I want to cover in this video. As usual, I want to invite you to visit the website. You know it. It’s at www.Interactive-Biology.com. There, you can get other Biology videos, and resources to help make Biology fun. This is Leslie Samuel, and I’ll see you in the next one.

About The Author Leslie Samuel

Leslie Samuel is the creator of Interactive Biology. He created this site to help Make Biology Fun and has the goal of making this the biggest and best biology resource on the net.

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http://www.youtube.com/watch?v=eQRODiedQhQ

A lot has happened over the last few months, so go ahead, watch the video, and then let me know what you think in the comments below.

About The Author Leslie Samuel

Leslie Samuel is the creator of Interactive Biology. He created this site to help Make Biology Fun and has the goal of making this the biggest and best biology resource on the net.

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Breathing is one of the most common things we do everyday to a point that it becomes unnoticed. Wouldn’t it be great to learn what happens behind this process? What exactly happens when we breathe air in and out of our body? Watch this video as Leslie teaches once again in such an easy way to make it all easy for us to understand this concept.

Have fun!

Transcript of Todays Episode

Hello and welcome to another episode of Interactive-Biology TV where we’re making Biology fun. My name is Leslie Samuel. In this episode, Episode 62, I’m going to be talking about pressure changes that happen during breathing. That’s what we’re going to talk about. Let’s just get right into it.

We’ve been talking about the respiratory system. We have been talking about the fact that you are breathing in. As air comes in, so let’s say the air is coming through here and then, it eventually ends up in the lungs. In the lungs, we can see here we have the alveoli. As the air comes in, that air can then give oxygen to the blood and it can take carbon dioxide and bring that into the cavity here and then, when you breathe out, of course, that air is going to go through the mouth and through the nose, depending on how you’re breathing and that’s going to push the air outside.

What we’re going to talk about is how this process of breathing actually happens and the pressure changes that are involved.

Here we have the two lungs. What I’m going to do is I’m going to draw an additional part here because this diagram is kind of simplified so, we’re just going to add a little more. We’re going to close this off and we are going to close that part off. And then, I’m going to give some names.

This entire section that we’re dealing with, that is called the thoracic cavity. In the thoracic cavity, we have this space right here. That space is called the pleural cavity. Then, we have one more cavity and that’s inside the lungs. We’re going to call that the pulmonary cavity. Another thing that we need to label here, this here is a muscle and that muscle we call the diaphragm. Beneath here we have the abdominal cavity but, we’re not going to talk too much about that. Actually, let me still label it here because we are going to mention it. Abdominal cavity.

What we’re going to talk about is what happens during breathing. Over here we’re looking at muscles and here you can see we have this group of muscles here and that is called the external intercostals. You can see it diagonally going here. Then, here we have the internal intercostals muscles. So, we’re going to talk about the things that happen during breathing and we’re going to mention what roles those play also.

When I’m breathing in, I’m taking a breath. I just breathe in. There are a number of things that are happening.

First thing is we have the diaphragm here and the diaphragm contracts. When the diaphragm contracts, that moves down. It kind of moves down here. Then, we have the external intercostals. When they contract, that moves the rib cage up. So the diaphragm is contracting; the external intercostals are contracting; this moves down, the external intercostals move the rib cage up and the overall effect is that we’re increasing the space of the thoracic cavity. So, we’re increasing the size of the thoracic cavity. When you increase the size, that is going to cause a decrease in pressure in the thoracic cavity. Of course, since you’re increasing the size and you’re pushing down here with the diaphragm, it’s increasing the pressure in the abdominal cavity, decreasing the pressure in the thoracic cavity. Of course then, that’s going to cause a reduction in pressure of the pleural cavity. When the pressure is reduced in the pleural cavity, that then becomes lower than the pressure inside the lungs in the pulmonary cavity.

Once again, diaphragm contracts, external intercostals contract. That expands the thoracic cavity, decreasing the pressure in the pleural cavity. If we have a lower pressure in here than in the lungs, what is going to happen to the lungs? Of course, greater pressure inside, lower pressure on the outside, the lungs are going to expand. As the lungs expand, now you have more space in here, that’s going to decrease the pressure in the pulmonary cavity, relative to the pressure of the atmosphere. That is going to cause air to move from higher pressure to lower pressure and the air is going to go in and, of course, go into the lungs.

Let’s review that again: Diaphragm contracts, external intercostals contract that expands the thoracic cavity, decreasing the pressure in the pleural cavity. Because that’s going to be now lower than the pulmonary cavity, that’s going to cause the lungs to expand causing a reduction in pressure in the pulmonary cavity. That’s going to cause air to move from the atmosphere into the lungs. And, we have just accomplished breathing in.

During normal breathing, what then happens when it’s time to, not inspire, but expire, so, exhale. The diaphragm and the external intercostal muscles are going to relax. Since we had a buildup in pressure here, when the diaphragm contracted, the abdominal cavity is then going to push against the thoracic cavity increasing the pressure in the pleural cavity, increasing the pressure in the pulmonary cavity causing air to leave. So, it’s the exact opposite.

First, we’re decreasing the pressure by expanding then, now we are increasing the pressure by making the cavity smaller, pushing the air out. That’s during normal breathing.

When you are breathing more intense and it’s more of a forced breathing situation, it’s very similar to what we just described except that there are other muscles involved. So, for inspiration, the diaphragm is going to contract, external intercostals are going to contract and also some neck muscles and we’re going to get air coming in. It’s a stronger contraction. So, that’s going to bring more air in because you’re reducing the pressure even more.

Then, when you’re breathing out, you’re not just relaxing the diaphragm but you’re also bringing in the internal intercostals muscles and those are going to contract and when those contract, the rib cage moves down, thoracic cavity gets smaller, faster of course, and that’s going to increase pressure faster, and cause more air to be pushed out into the atmosphere.

Overall, you’re breathing in because you’re decreasing the pressure on the inside, you’re breathing out because you’re increasing the pressure on the inside.

That’s pretty much all for this episode. As usual, if you want to find more of these videos and other resources I’d like to invite you to visit the website at Interactive-Biology.com. That’s it for this video and I’ll see you on the next one.

About The Author Leslie Samuel

Leslie Samuel is the creator of Interactive Biology. He created this site to help Make Biology Fun and has the goal of making this the biggest and best biology resource on the net.

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What happens when the pH decreases during cellular respiration? What effect does this have on the hemoglobin’s affinity? What is the Bohr effect?

You can find the answers on this video as Leslie explains more about what happens during cellular respiration.

Have fun!

Transcript of Today’s Episode

Hello and welcome to another episode of Interactive-Biology T.V. where we’re making Biology fun! My name is Leslie Samuel and in this episode, Episode 61, I’m going to be explaining the Bohr Effect. So, let’s get right into it.

Now, we’ve looked at this oxygen dissociation curve of hemoglobin in Episode 60 and, we showed how as oxygen is taken up by hemoglobin that increases the affinity and makes it easier for more oxygen to bind. As oxygen is released, it makes it easier for more oxygen to be released and, oxygen leaves the hemoglobin and goes into the tissues and is released so that, it can be used by the tissues, the muscles, and so on and so forth. You can review that in Episode 60 and, in Episode 59, I gave an introduction to the respiratory system. And, the key formula we looked at (let me write that up here in red) was:

You can revisit that in Episode 59 for a review on that. This is glucose (C6H12O6), this is oxygen (6O2) then, we have carbon dioxide (6CO2) being produced and, also water (6H2O) being produced.

Now, taking this and also looking at the oxygen dissociation curve, as carbon dioxide is produced, there’s another reaction that comes into play (and I’m going to show that over here in blue), and that reaction is CO2, carbon dioxide, plus H2O, that is going to give, and this can go both ways, that’s going to give H2CO3 and then, of course, since this is water, we can end up with H+  +  HCO3-:

This guy here (H2CO3) is carbonic acid, so, it’s an acid that’s why if it’s in water, it will disassociate and will get hydrogen ions (H+) and bicarbonate (HCO3-).

Now, when carbon dioxide is produced, that can cause the formation of carbonic acid and that’s going to release hydrogen ions. What is that going to do to the pH?

Well, of course, that’s going to cause the pH of the blood to decrease, so we’re going to decrease pH. I’m not going to go into too many details about what pH is but, that has to do with the acidity of the blood. If the pH goes down, it’s more acidic. If the pH goes up, it’s going to be more basic.

When the pH goes down, what that ends up doing is it reduces the affinity of hemoglobin for oxygen. So, hydrogen ions produced causes a reduction in pH, and that is going to influence the hemoglobin in such a way that the affinity for oxygen is going to be decreased and it’s going to release more oxygen than it normally would. This is called, or at least this is part of the Bohr Effect. And, I should put this with a capital ‘B’ because this is named after Christian Bohr who was the first person to describe this and, that is why we call it the Bohr effect.

So, decrease in pH decreases hemoglobin’s affinity for oxygen and, we get the Bohr effect. How that appears in the oxygen dissociation curve is that the curve actually shifts to the right. You can see this dotted red line here and, what that shows is we have a lower affinity for oxygen. So, for example, if the partial pressure of oxygen (PO2) is around 42 mmHg, normally, the hemoglobin would be approximately, what is that, 73-ish, 74-ish percent saturated with oxygen, however, because we have this Bohr effect and it shifts to the right at that same partial pressure of oxygen, we have a percent saturation of approximately 63 or 64. So, we get a 10% reduction by changing the pH by a certain amount. So, we reduce the pH, affinity for oxygen goes down, and that is called the Bohr Effect.

Now, this is one part of the equation that is a result of decreasing pH which is also a result of increasing carbon dioxide. This is a very important because, if you’re in the gym, you’re exercising, you’re working out, cellular respiration is happening even more and not only that but, if you’re exercising to the point you go into anaerobic respiration, you get lactic acid buildup and that of course is also an acid, that’s going to decrease the pH even more, decreasing the affinity for oxygen. And, you want that to be the case because this also means that more oxygen is going to be released. So, by producing more carbon dioxide because cellular respiration is happening even more, it decreases the acidity in the tissues, in the muscles, and when the blood passes there, it’s going to release more oxygen.

Now, there’s another equation that comes into play, and that also has to do with carbon dioxide. Because on the hemoglobin, you also have N-terminal amino groups (so, I’m going to write that here as) R – NH2. So, this is the N-terminal. And, in the presence of carbon dioxide (CO2), once again, that is going to cause a reaction where we are forming, and this is called carbamate (R – NH – COO-), plus H+:

So, we also have that hydrogen ion being produced here that of course, is going to decrease pH even more.

Now, what this carbonate is going to do, this is going to enhance deoxyhemoglobin stability. In other words, hemoglobin will be more stable in the deoxygenated form. In other words, it’s going to want to give up more oxygen, and of course, the hydrogen ion is also going to cause the oxygen release as we showed over here because you are decreasing pH, decreasing the affinity for oxygen. So, you can see carbon dioxide is doing this in two ways. It’s doing it by decreasing the pH; it’s doing it by producing carbamate and, that is going to enhance the deoxyhemoglobin stability. In other words, it’s more stable without oxygen so, it’s going to release oxygen, and you’re going to get this Bohr effect or the Bohr shift where the graph moves to the right, which is a good thing once again because more oxygen will be delivered to the muscles, to the tissues that need them.

That’s pretty much it! I hope that make sense with all these equations that we have here: cellular respiration, formation of bicarbonate by means of carbonic acid, and the formation of carbamates which enhances the deoxyhemoglobin stability.
That’s pretty much it for this video. As usual, if you want to see more of these kinds of videos, you can visit the website at Interactive-Biology.com. And, you’re going to get videos, quizzes and other resources to help make Biology fun. That’s it for now and, I’ll see you on the next one.

About The Author Leslie Samuel

Leslie Samuel is the creator of Interactive Biology. He created this site to help Make Biology Fun and has the goal of making this the biggest and best biology resource on the net.

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http://www.youtube.com/watch?v=MKGhoC1Bf-I

Click Here to Download This Video

Ever wonder how the oxygen binds to our blood cells and sent to the different parts of our body? Watch and learn with Leslie as he explains how this happens and uses the Oxygen-Dissociation Curve to describe this event.

Have fun!

Transcript of Today’s Episode

Hello and welcome to another episode of Interactive-Biology T.V. where we’re making Biology fun! My name is Leslie Samuel and in this episode, Episode 60, I’m going to be talking about hemoglobin and what’s called the oxygen-dissociation curve. So, let’s get right into it.

We’ve already done an introduction to the respiratory system and we’ve shown how the heart beats and sends the blood. When the right ventricle sends the blood, it sends it to the lungs that comes back to the left atria and then, the left ventricle pumps and that sends the blood through the rest of the body.

We’ve also looked in the lungs and seen how we have the trachea going into the bronchi and then that splits off into the bronchioles, and as you can see here, that gives us the alveoli and it’s in the alveoli where we have the exchange between the oxygen coming into the bloodstream, via the capillaries that we have here, and the carbon dioxide leaving the capillaries going into the lungs and being sent from the body.

Now, when the blood comes in here, it is picking up oxygen, and the type of blood cells that are picking up the oxygen, would be the red blood cells. Here you can see a picture of a few red blood cells, of course, it’s simplified. It’s not showing the white blood cells or anything else. It’s just showing the red blood cells and these are the blood cells that pick up that oxygen.

In the red blood cells, we have special molecule. That molecule is called hemoglobin. You can see a three-dimensional image here of the structure of hemoglobin so, this is, (let me write it here), hemoglobin. This molecule, it’s actually a protein, and this protein is the protein that is responsible for picking up the oxygen.

Now, let’s go into a little more detail. You can see here, that we have these four structures. Those four structures are called, (let’s do that in blue), those are heme groups. All right, so these are the four heme groups. The special thing about these heme groups is that those are the parts where the oxygen is attracted, so, we have O2 that actually comes and binds to the heme groups. As you would imagine since we have four heme groups, we can take a total of four oxygen molecules. So, this is one oxygen molecule here, and we can have another oxygen molecule here, here, and also here. So, this hemoglobin molecule once again, has a capacity to hold four oxygen molecules.

What’s interesting about the hemoglobin is that whenever one oxygen binds to a heme group, that causes the entire hemoglobin structure to undergo a conformational change so, basically changing the site of the molecule whenever one oxygen binds. As you can see here, this is the heme group but, there’s stuff around on it, and you can imagine that it would be relatively hard for the oxygen to get in there and find the right spot.

However, when one binds, it causes a change which opens it up a little bit to make it a little easier for another oxygen to come in and bind. And, when that other oxygen comes in and bind, it causes another conformational change, making it easier for another oxygen to come and bind and, once again, once that oxygen comes and binds here, it makes it easier for another oxygen to come in here and bind to it. So, in other words, as it starts taking up oxygen, it makes it easier for it to take up more oxygen. And then, of course, the opposite will be true. If we have a hemoglobin molecule that has four oxygen attached and, for some reason it gives up one oxygen, that’s going to cause a change that makes it a little harder for the other oxygen to bind. In other words, it becomes easier for oxygen to leave. So, as oxygen leaves, it’s easier for more to leave; as oxygen binds, it makes it easier for more oxygen to bind.

As a result of this, we get a relationship that is shown in this oxygen-dissociation curve. And, what you can see here is, (we’re going to be looking at this blue line) and, as you can see here, it’s not a linear relationship. In other words, as the amount of oxygen increases, so here, we’re showing the pressure of oxygen, as the pressure of oxygen increases in the environment that the hemoglobin is in, you’re going to get more binding, making it easier for more to bind, making it easier for more to bind, and the graph is going to increase faster as you’re going to the right where you have an increased partial pressure of oxygen.

Not a linear relationship but, as some binds it becomes easier so, more bind faster and it becomes easier and it gets faster and faster until, of course, it reaches to where it’s getting saturated and, it dies off.

Now, you might be wondering why it’s not just four-levels since we only have four binding spots for the oxygen, the four heme groups. However, this is not looking at one hemoglobin molecule. This is looking at a bunch of hemoglobin molecules in a bunch of red blood cells and, overall, as some starts binding, it makes it easier and easier so, it’s going to increase faster and faster until it reaches to the saturation and then, it’s going to slow down when it reaches its full saturation.

Also, as you come in this direction, as the pressure of oxygen decreases, and oxygen starts to leave, here it’s leaving slowly but, as it starts to leave more, it’s dropping down faster, and faster, and faster, until all of the oxygen is gone.

So, this is the oxygen-dissociation curve showing once again, as you pick up oxygen, it makes it easier for oxygen to be picked up, so here it starts slow and it goes faster and faster and faster and as you release oxygen, it makes it easier for oxygen to leave and then, that goes down faster and faster. This is called the oxygen-dissociation curve.

That’s pretty much it for this video. If you want to see more videos like this and check out the other resources we have available, visit the website at www.interactive-biology.com.

That’s it for this video and I’ll see you on the next one.

About The Author Leslie Samuel

Leslie Samuel is the creator of Interactive Biology. He created this site to help Make Biology Fun and has the goal of making this the biggest and best biology resource on the net.

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http://www.youtube.com/watch?v=aoa50sd7lWM

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We are off to start learning from a new set of videos about another part of the human body system and here, Leslie opens a new topic with a brief introduction of the Respiratory System.

Watch and enjoy!

Transcript of Today’s Episode

Hello and welcome to another episode of Interactive-Biology T.V. where we’re making Biology fun! My name is Leslie Samuel and in this episode, Episode 59, I’m going to be giving an introduction to the respiratory system. So, we’re changing gears now. We just finished talking about the circulatory system and, now, we’re going to talk about a system that is very closely linked to the circulatory system that is, the respiratory system.

So, let’s get right into it. Here, we’re looking at a bunch of ladies. These ladies are exercising. They are working out in the gym. Some of them are on the, like over here you can see we have one on an elliptical then, we have some riding exercise, bikes and lifting some dumbbells here and boxing a punching bag, punching a punching bag and there’s a lot going on right here. There’s one thing that these ladies all have in common, well, there are a number of things that these ladies have in common. They’re all attractive that’s one. They’re all exercising but, the thing that I want to focus on is that they are all breathing. I hope that make sense. They are all breathing, they are working out and in order to be able to get the energy that they need, they need to be breathing in oxygen. There are a number of things that have to happen in that process and we are going to talk about that today. So, whether you’re exercising or you’re just standing still or even if you are sleeping, you need to be breathing if you’re going to be alive of course, and we’re going to be talking about that today. So, let’s get right into it.

In order for us to have energy, there is a process that needs to happen and this process is called, ‘cellular respiration.’ Now, we’re not going to go into too much detail in terms of cellular respiration in this episode but, we are going to come back to it. The main thing that I want us to look at is the formula for cellular respiration, and that formula is:

If you’re a biologist, you’re into Biology, you’re in a Biology class, or whatever the case might be, I think, it’s imperative for you to know this formula. So, memorize this formula:

Now, let’s give some names to these bad boys. This guy over here (C6H12O6), that is none other glucose, okay so that a carbohydrate, it’s a type of sugar. O2, you should know that is oxygen. And then, of course CO2 is carbon dioxide and H2O, if you don’t know this, something is wrong, that is water. Well, maybe nothing is wrong, maybe you just never heard of it before. But, anyhow so, we have glucose that’s reacting with oxygen and the products, so these are the reactants on the left, the products on the right are carbon dioxide and water. And this right here is the general equation for cellular respiration. It is an oversimplification but, it gives you the things that are necessary and the things that are produced. Now, glucose, where do we get this from? Well, of course, we eat, right? We take in some food and we get glucose. So, let’s say we get this (glucose) from eating, oxygen, we get this from breathing, there’s oxygen in the air and, when we breathe, we bring in that oxygen that we need. Carbon dioxide, this is actually a waste product. We’re producing this but, we don’t actually use it. When we breathe, we breathe that out and that goes into the air, and that’s used by plants and plants can use that for photosynthesis. Water, do we need water? Yes, of course we need water. I’m not going to write anything right here because it’s just water. Water is essential for life and we are actually producing water in this process of cellular respiration.

In doing this entire thing, one of the things that we are making, or the main thing that we are making is energy. But, in order to make that energy, in order for us to get that energy when we’re exercising, walking, whatever we’re doing, we need to have oxygen. This oxygen needs to come in and, this is why we are breathing in, we’re taking in the air, and in the air, there is oxygen. And of course, we need to get rid of the carbon dioxide so, when we breathe that out, that is getting rid of the carbon dioxide. It’s doing some other things but, this the main function, the main functions of the respiratory system. We want to take the good stuff in, which in this case is the oxygen, and we want to take the bad stuff out, which in this case would be carbon dioxide. So, memorize this equation if you haven’t already, know what the components are and where they come from.

Let’s continue now. We’ve been looking at the circulatory system and, we’ve looked at over here, we have the heart and that heart is very important because it allows us to circulate the blood through our circulatory system and, one of the things that the heart does before it sends blood to the body is it sends the blood to the lungs. You can see here that the pulmonary vein is going away from the heart and that takes blood to the lungs, this is the lungs right here, and then, that blood takes up oxygen and comes back to the left ventricle and the left ventricle then pumps the blood via the aorta to the rest of the body. We’ve looked at that in previous episodes. If you do not remember, you can visit the section that’s right before this and you will get a review on that.

Now, what we’re going to do here, this is looking at the lungs but, it’s not looking at the lungs in detail. So, what we’re going to do is come over to this guy over here which is not showing the circulatory system but, it’s showing the respiratory system. And, you can see here we have the lungs and then, we have the mouth here, the oral cavity, which then goes into the pharynx and then, to the trachea and then, that takes us to the bronchus and the bronchioles and then, that goes into alveoli, and then, we can take this section here and you can see a larger area of the alveoli.

Not only that, we don’t only breathe in through our mouth, we also breathe in through our nose and, you can see the nasal cavity here is also leading into the pharynx which then goes the same route via the trachea and so on and so forth.

And, what I want you to notice is that when we look at this small section and, we look here at the alveoli, you can see that the pulmonary vein is coming in and then, it’s forming these capillary beds, and then, you can see the pulmonary artery is then going out. I want you to also notice the colors. Here, it’s showing red and this is when there’s no oxygen in the blood but as it comes into the capillary beds, and we are breathing in the air that’s coming in through the trachea, and the bronchus and the bronchioles to the alveoli, you can see here that when the oxygen gets in here, that can then go into the capillary beds and you see this color changing from red to kind of purplish and then to blue because it’s taking up that oxygen and then, that oxygenated blood is going via that pulmonary artery back to the heart.

There’s another thing that I want to mention here because I’m just giving an introduction so we’re going to go into more detail and all of these aspects later but, here we have the diaphragm, which is a muscle, and there are other muscles that are involved, and when those muscles contract, it causes the lungs to expand and, we breathe in air that has oxygen. The oxygen then gets taken into the blood stream and that goes back to the heart and the heart can then pump that oxygenated blood through the rest of the body.

Not only that, but, as the blood comes to the alveoli, it’s also bringing with it carbon dioxide. Remember that carbon dioxide that we made in cellular respiration, that’s bringing that carbon dioxide. That carbon dioxide can then go into the alveoli and then, when we breathe out, that carbon dioxide comes out via the alveoli and through the bronchioles and the bronchus and the trachea and then, through the pharynx and then either through the oral cavity or the nasal cavity.

So, we’re getting that bad stuff out, we’re getting the good stuff in. That is what the respiratory system is all about.

So, there you have it. That’s just kind of a brief overview. I kind of glossed over a lot of the details because I’m going to be getting into those details in future episodes.

But, for right now, I want to invite you to visit Interactive-Biology.com and, you will find more Biology videos, quizzes, games, a whole bunch of resources, you want to check them out. So, that’s it for this video and, and I’ll see you on the next one.

About The Author Leslie Samuel

Leslie Samuel is the creator of Interactive Biology. He created this site to help Make Biology Fun and has the goal of making this the biggest and best biology resource on the net.

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http://www.youtube.com/watch?v=OP4Xh4oawG8

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How do the differences in hydrostatic and osmotic pressures affect the flow of blood within the circulatory system and to the different parts of the body? What is filtration pressure and how are these affected during abnormal conditions such as having a high blood pressure?

Watch and learn with Leslie as he explains further about this topic. Have fun!

Transcript of Today’s Episode

Hello and welcome to another episode of Interactive-Biology TV where we’re making Biology fun! My name is Leslie Samuel and in this episode, Episode 058, I’m going to be talking about “Net Hydrostatic Pressure and Filtration Pressure.” Let’s get right into it.

Now, we’ve been looking at the circulatory system and we’ve shown that the blood leaves the heart and then, it goes via the aorta to the arteries and then, to the capillaries, to the venules, to the veins and then, to the vena cava, and then, ultimately, back to the heart. If you need a review of that, you can always check out Episode 054 where we go into more detail about that.

What we’re going to be doing today is we’re going to be looking at what happens between the arterioles, the capillaries, and the venules. That’s what we’re showing here. We have an artery leading to the arteriole and then, that goes to the capillary bed and then, that goes via the venules to the vein. What we’re going to look at is what happens specifically right here. The goal here is we want to get blood coming to the tissues delivering nutrients and so on, oxygen to the tissues and then, taking stuff away. So, taking away waste and so on.

What I’m going to do here is I’m going to simplify this a little bit. I’m going to show this like this. I’m going to take from the arterioles to the venules. I’m going to simplify it showing one arteriole that connects to one capillary, and then, that’s going to connect to one venule. I’m simplifying this significantly. Here we have the arteriole, here we have the venule, and here we have the capillary (I’m not going to put the ‘c’ here, but, here we have the capillary).

The main things that we’re going to focus on are the different pressures that we have in this setup. Now, of course the heart is pumping and the blood is coming in this direction, and then, it’s going via the capillaries. This is where the exchange happens because this is where we have the tissue and, this is where we want to get stuff delivered and we want to pick up stuff to take away from the tissues.

The first thing we’re going to talk about is ‘net hydrostatic pressure.’ I’m just going to write NHP for net hydrostatic pressure. When we’re talking about hydrostatic pressure, we are talking about pressure due to the fluids. Of course, in the blood we have fluids. In the tissue we also have fluids. The net hydrostatic pressure, as the blood is coming in here, of course there’s going to be a blood pressure because the heart is beating, it’s pumping the blood, and we’ve looked at blood pressure in previous episodes, and as the blood goes through the capillaries, there’s going to be friction that it’s encountering. It’s going to be bumping against the walls of the capillaries, and that is going to actually reduce the pressure. What we’re going to end up with is a high amount of pressure here and that’s going to drop down as we go along the capillaries. But, not only that, we have tissue here that’s filled with fluid also and that’s also going to exert a pressure on the capillaries.

The net hydrostatic pressure, we’re talking about the total hydrostatic pressure, that is going to be equal to the blood pressure, so the blood is pumping out, and we’re going to subtract the tissue pressure. So, the blood pressure, how much it’s pumping out and how much it’s pushing in from the fluids in the tissues. That net hydrostatic pressure is going to be greatest going out closer to the arterioles. So, we have a lot of hydrostatic pressure pushing out and, as we go down, and the blood is bumping against the walls and so on, that amount of pressure is going to decrease. This is what I’m illustrating here, it’s going down, going down, and when I reached to the end, we’re going to have the least amount of hydrostatic pressure which makes sense, as I said before, the blood is coming via the arteries to the arterioles. It’s coming because the heart is pumping it, and with that pumping we’re going to get a lot of pressure.

That’s going to be highest here, but, because this tube is so small, we have a tiny tube almost to the point that the blood cells can only get through one at a time. That is going to cause a lot of friction, and that is going to decrease the amount of pressure. If I take something and I push it across a surface, because there’s going to be friction with that surface it’s going to slow down. And, that’s exactly what we’re getting here. The amount of pressure is going to decrease as we go away from the arterioles and towards the venules. So, the net hydrostatic pressure is what we’re looking at here.

We’re going to get stuff leaving, but, not everything can leave. Blood cells aren’t going to leave but, water is small enough to get through the pores in the capillaries. So, water is going to leave. It’s going to take some oxygen with it. It’s going to take nutrients with it and so on. That is going to leave the capillaries which is exactly what we want because we want to deliver that stuff to the tissues or to the muscles or to whatever it is this capillary is going through. This is a good thing but, as the water is leaving, of course, we’re going to get less and less water inside the capillaries. Because of that, we’re going to have a change in osmotic pressure. Now, if you remember osmosis is the movement of water across a selectively permeable membrane. We have a selectively permeable membrane here.

What is going to happen is water leaves here, there’s going to be a little bit of osmotic pressure for water to come back in. As more water leaves, we’re going to get an increase in osmotic pressure and then, we’re going to get an even greater increase in osmotic pressure. That’s going to continue of course, and this is exactly what we’re going to see.

As the net hydrostatic pressure goes down, the net osmotic pressure is going to increase and increase and increase. When we take this together, we’re going to get the filtration pressure, (I’m going to write FP), and that’s going to be equal to net hydrostatic pressure minus net osmotic pressure: FP = NHP – NOP. These are not the official symbols. This is just what I’m writing for simplification. But, you can see that we’re going to get a filtration pressure. If we’re over here and we’re taking this hydrostatic pressure minus this osmotic pressure, we’re going to see that we’re going to have a net filtration pressure moving stuff out. That’s going to decrease as we go here to where in the center, the filtration pressure is going to be zero because we have this amount coming out and this amount going in. And, just to make that more equal, I’m just going to draw the rest of that arrow here. Then, of course, as we go down here, we have more pressure, going in, the osmotic pressure is significantly greater, so, we’re going to get a filtration pressure that’s pointing into the capillaries, moving stuff in.

So, over here, we’re moving stuff out. Over here, we’re moving stuff in. And if I were to draw a graph, I’m just going to draw a graph over this, I’m not sure why I did that as a dotted line, this is the y-axis and we’re dealing with filtration pressure, and let’s say this is the zero line. What we’re going to have is a filtration pressure that looks something like this. Here we have it moving out, so it’s going to be somewhere around here, and of course, that’s going to go down to zero at this point, and then, continue going down, showing that we have a negative filtration pressure or in other words, a pressure moving stuff into the capillaries. Here is ‘moving out of’ and here we’re ‘moving stuff into.’

This point right here, where we have a filtration pressure of zero, that is called the ‘dynamic center.’ This is where the net hydrostatic pressure is equal to the net osmotic pressure — equal but, and opposite of course — and that is called the dynamic center. In a perfect world, this dynamic center is exactly where we want it to be so that, we have a good amount of distance for stuff to leave and a good amount of distance for stuff to come in. So, we’re delivering the nutrients and the stuff that we need to the tissue, and we’re taking away the waste and the stuff that we don’t want sending that away from the tissues.

I want to look at a different scenario, where we have the same setup. We have the arteriole, the capillary and the venule going back to the veins, and vena cava, and back to the heart. But, in this situation, we’re going to be dealing with someone that has high blood pressure. So, here, we’re going to have a significant amount of net hydrostatic pressure pushing stuff out. So, it’s much higher. What that’s going to do, as you can see here is the pressures are going to be greater all the way along. Yes, it’s decreasing but, because we’re starting with a higher amount, we’re also going to end with a higher amount.

We also have the osmotic pressure doing the same thing that it was doing before and, stuff is leaving, and let’s say, we have it here, and this is kind of extreme and let’s say that because of this high blood pressure, we still have the filtration pressure here, we have the osmotic pressure here. But, the dynamic center, instead of being over in the center, the dynamic center is somewhere around here. Now, that is a significant problem because this is what we have. In this entire section we have this fluid leaving and, it’s not until here that we have a net amount of fluid coming in. What’s that going to do is it’s going to cause more fluid to be leaving than the amount of fluid that’s coming in, and that is going to result in accumulation of fluid in the tissues or, we can also call that, edema. So, this can be a result of high blood pressure because we have more fluid leaving the capillaries than coming into the capillaries. We have more going towards the tissues and that can cause a significant amount of problems resulting in edema.

So, the take home message, net hydrostatic pressure is blood pressure minus tissue pressure. That’s what we’re showing here. And, if we want to find the filtration pressure, we take net hydrostatic pressure minus net osmotic pressure. That will give us that filtration pressure. To this side of the dynamic center, the filtration pressure is moving fluids and dissolved molecules out of the capillaries. As we come to this side, it’s moving fluids into the capillaries. If we have high blood pressure, that can shift the dynamic center significantly resulting in accumulation of the fluids in the tissues or edema.

That is pretty much it for this episode. As usual, I’d like to invite you to visit the website at Interactive-Biology.com for more Biology videos and other resources. That’s it for this video and I’ll see you on the next one.

About The Author Leslie Samuel

Leslie Samuel is the creator of Interactive Biology. He created this site to help Make Biology Fun and has the goal of making this the biggest and best biology resource on the net.

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http://www.youtube.com/watch?v=DfAyZwsIYR4

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Here is an interesting concept about pressure reflexes that you might want to watch. It is related to the mean arterial pressure of a man. Learn more by watching another one of Leslie’s easy videos to help you understand these concepts easier.

Have fun!

Transcript of Today’s Episode

Hello and welcome to another episode of Interactive-Biology TV where we’re making Biology fun! My name is Leslie Samuel and in this episode, Episode 57, I’m going to talk about, ‘Pressure Reflexes and Mean Arterial Pressure.’ We’ve been talking about mean arterial pressure a lot, we’ve spoken about cardiac output and peripheral resistance. You can always revisit previous episodes to find out more about them.

Today, we are talking about pressure reflexes. We’ll look exactly at why we call it pressure reflexes. Here we have the heart (I feel like I keep saying that in very episode recently) and the heart, it pumps the blood throughout the body. We have the aorta.

One of the arteries that I have not been talking about would be the carotid artery. This is the common carotid. I’m just going to come here and draw a line here and say, that we’re dealing with carotid arteries. Of course, here, we are dealing with the aorta.

There is something very special that we have in these two arteries. In both the aortic and the carotid bodies, we have receptors that we call ‘baroreceptors.’ From the time you hear the prefix ‘baro-,’ you should know that it has something to do with pressure. For example, a barometer measures pressure and, here we have baroreceptors and these baroreceptors respond to changes in, you guessed it! Pressure. That is why they are called baroreceptors.

What’s going to happen is, if we have an increase in the mean arterial pressures, so we have a significant increase in mean arterial pressure, what that’s going to do, these baroreceptors are going to start firing. We’re going to have an increase in the firing of these baroreceptors. In other words, they’re going to be sending signals. Those signals are going to a region in the brain stem that we call the medulla. This is known as the “blood pressure regulating center.” Of course, it regulates other things but, it also regulates pressure.

That then, is going to cause a combination of two things. It’s going to cause an increase in parasympathetic activity and going to cause naturally a decrease in sympathetic activity. If you remember from one of the early episodes, sympathetic activity causes stuff like increase in heart rate, increase in blood pressure, and so on. Parasympathetic activity calms stuff down so, it reduces blood pressure, it reduces heart rate, breathing rate, and so on. So, we have an increase in mean arterial pressure, so an increase in blood pressure, the baroreceptors are going to respond by sending signals to the medulla. That’s going to cause an increase in parasympathetic activity, calming stuff down, and a decrease in sympathetic activity. Sympathetic activity would normally increase pressure, and speeds stuff up but, here we’re slowing that down. So, the net result of these two things is we’re going to get a reduction in cardiac output and also in peripheral resistance. Then, of course, that is going to cause a reduction in mean arterial pressure.

This is why we call it a reflex because we have an increase in mean arterial pressure, and that’s going to cause a number of things that’s going to eventually cause a reduction in mean arterial pressure. The relationships between these quantities here, we’ve looked at a number of times, and, just to revisit that:

M.A.P. =CP x PR,

Mean arterial pressure is equal to cardiac output times peripheral resistance. Since we’re decreasing both cardiac output and peripheral resistance, we are also going to decrease mean arterial pressure.

That’s pretty much it for this episode. Of course, you can always visit the website at Interactive-Biology.com for more Biology videos, more Biology resources, and more Biology fun. That’s it for now and I’ll see you in the next one.

About The Author Leslie Samuel

Leslie Samuel is the creator of Interactive Biology. He created this site to help Make Biology Fun and has the goal of making this the biggest and best biology resource on the net.

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http://www.youtube.com/watch?v=MRcra9oxrXY

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Here is the second part of Regulating Peripheral Resistance. Leslie explains two more ways on how it can be influenced and how it affects someone’s blood pressure and mean arterial pressure. Watch to learn more!

Have fun!

Transcript of Today’s Episode

Hello and welcome to yet another episode of Interactive-Biology TV where we’re making Biology fun! My name is Leslie Samuel and in this episode, Episode 56, I’m going to continue talking about, ‘Regulating Peripheral Resistance.’ This is part 2, and I think this is going to be the final part about this. So, let’s get directly into the content for today.

In the last episode, we emphasized, we re-emphasized the fact that mean arterial pressure is equal to cardiac output times peripheral resistance (M.A.P. = CO x PR). We’ve spoken about the fact that we are modifying peripheral resistance. We’re looking at the different ways in which peripheral resistance is influenced. In the last episode, you can go back to Episode 55, we spoke about vasoconstriction and we said that that is going to cause an increase in peripheral resistance. We spoke about vasodilation which is going to cause a decrease in peripheral resistance.

We’re going to talk about two other ways in which we can influence peripheral resistance. The first way that we are going to talk about today is called, blood viscosity. By viscosity what I mean is basically the thickness of the blood. This is very logical.

For example, a few weeks ago I was in Colombia and we remember we went to a restaurant and I ordered a mango milk shake. The milk shake was very, very, very thick. I was sucking on the straw trying to get it out and it was really hard to get that mango, I mean it was a very good tasting mango milkshake but, it was hard to get it in my mouth because of how thick it was.

This is the same thing. The thicker the blood is, the more resistance we’re going to have to blood flow. If we increase blood viscosity, we’re going to increase peripheral resistance significantly. By the viscosity, specifically, I am talking about the ratio of RBCs (red blood cells) to the blood plasma:

RBCs : plasma

By plasma, we’re basically talking about the fluid. If we have more red blood cells, or we increase the ratio of red blood cells to plasma, we are increasing the thickness of the blood. So, the overall message is, and let me just divide this in two, if we increase blood viscosity, that of course is going to result in an increase of peripheral resistance. On the other hand, if we (let’s use a different color), decrease blood viscosity, that is going to cause a decrease in peripheral resistance.

What is an example of a way we can increase blood viscosity? Well, for example if we are dehydrated. What that’s going to do is it’s going to reduce the amount fluid in the blood, so the plasma is going to be less. That is going to cause an increase ratio of red blood cells to the plasma, we’re going to have an increase in blood viscosity, and that’s going to cause an increase in peripheral resistance.

What can cause decrease in blood viscosity? For example, loss of blood volume due to anemia or if there’s hemorrhage, that’s another example (forgive my R’s… My students always make fun of me for my R’s). If there’s anemia or hemorrhage, that’s going to cause a decrease in blood viscosity causing a decrease in peripheral resistance. So, the first that we’re looking at today is by influencing blood viscosity.

The second way is by looking at the total blood vessel length. The message here is, the longer the blood vessels, the higher is the peripheral resistance. So, if you increase the blood vessel length, you are going to naturally increase peripheral resistance. That should also make sense. If something is much longer, you have a tube that’s very long, it’s going to be much harder to get the blood through. If my straw for my mango shake was extremely long, let’s say that straw was two-feet long, that would take a lot of work for me to get that great tasting mango shake into my mouth because it’s longer, increase in peripheral resistance.

Now, how would this translate to the human being? I’ll give you a very good example in America and other places also. If someone is overweight, what that’s going to do is that’s going to naturally increase blood vessel length. I’m going to give you some numbers right now that can be very disturbing. Or, it can’t be very disturbing depending on how you look at it. If you gain 2.2 pounds of weight of additional fat, that is going to add approximately, and this is very scary, 400 miles of blood vessels. That’s one kilogram of fat and approximately 650 kilometers of blood vessels. So, you can see, by gaining weight, you’re gaining more blood vessels. That’s basically increasing the blood vessel length, and that is going to increase peripheral resistance. And we know what increase in peripheral resistance will do to mean arterial pressure and to blood pressure because, we keep coming back to this:

M.A.P = CO x PR

More fat, longer blood vessels, increased peripheral resistance, and that is going to cause an increase in mean arterial pressure.

I guess, the take home message for today is, watch your weight.

That’s pretty much it for this episode. As usual, I want to invite you to check out the website at Interactive-Biology.com for more Biology videos and other resources. You can join the community over there, ask your questions in the forums, and just take part in everything that we have going there. That’s it for this video and I’ll see you in the next one.

About The Author Leslie Samuel

Leslie Samuel is the creator of Interactive Biology. He created this site to help Make Biology Fun and has the goal of making this the biggest and best biology resource on the net.

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