tag:blogger.com,1999:blog-14408634794145920062026-05-06T23:07:52.847-07:00Akshay S Dineshhttp://www.blogger.com/profile/13477111115934396454noreply@blogger.comBlogger2125tag:blogger.com,1999:blog-1440863479414592006.post-34138079918466092252012-06-02T10:58:00.000-07:002012-06-02T10:58:03.438-07:00<div dir="ltr" style="text-align: left;" trbidi="on"> Respiration is regulated by a set of nuclei in the brain stem.<br /> <br /> In the medulla there are two groups of nuclei that directly excites breathing muscles. <br /> <br /> Most importantly, there is the dorsal group of nuclei in the Nucleus Tractus Solitarius (sounding like Maximus Decimus Meridius&nbsp; it has a very important function like the hero too) which causes a (normally 2 second long) ramp like inspiration followed by a 150% duration pause, starting from the <i>limiting point</i> of inspiration, during which the lung expires due to elastic recoil.<br /> <br /> There is also a ventral (ventrolateral) group of nuclei (nucleus ambigus and nucleus retroambigus) which contain some nuclei that will cause inspiration and mostly nuclei that causes forceful expiration. (important in heavy exercise)<br /> <br /> Now, controlling both of these from above, from upper pons, is the pneumotaxic centre in the parabrachialis nucleus. It increases the rate of respiration by causing the cut off of inspiration early - taking breath rate at 30 to 40 per minute (like a hurry up!!) But if it is like a lax English teacher, the rate of respiration can drop down to 3 to 5 breaths per minute.<br /> <br /> Hering Breur reflex - a pneumotaxic centre like effect exerted through the vagii by the stretch receptors of the bronchi<br /> <br /> Chemicals?<br /> <br /> Oxygen, Carbon dioxide. These are what respiratory system is known for. And, carbon dioxide in blood is intricately tied to Hydrogen ion concentration.<br /> <br /> There is a chemosensitive area 0.2 millimeter deep to the ventral surface of medulla.<br /> This is highly sensitive to hydrogen ions.<br /> But, blood brain barrier doesn't allow hydrogen ions through.<br /> Whereas, it readily allows Carbon dioxide in.<br /> And carbon dioxide is not sensed too much by the chemosensitive area.<br /> But, the carbon dioxide readily combines with water to form carbonic acid which liberates hydrogen atom and causes the chemosensitive area to exert stimulation on the respiratory centres thus increasing the breath rate.<br /> <br /> For oxygen, it's like the chemosensitive area is located far away. Indeed they are: carotid bodies where common carotid artery splits send impulse through Hering’s nerve to glossopharyngeal nerve.<br />Aortic bodies along arch of aorta impulse through the vagi.</div>Akshay S Dineshhttp://www.blogger.com/profile/13477111115934396454noreply@blogger.com0tag:blogger.com,1999:blog-1440863479414592006.post-91447934118395290602012-02-21T04:29:00.001-08:002012-02-21T04:29:21.065-08:00<div><p>Physiology is that which connects the <a href="http://thelanesofhumanbody.blogspot.com">Anatomy</a> with the <a href="http://themedicalbiochemistryblog.blogspot.com">Biochemistry</a></p> </div>Akshay S Dineshhttp://www.blogger.com/profile/13477111115934396454noreply@blogger.com0