Phgy 210 – Gastric System 5

Phgy 210 – Gastric System 5 -...

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Phgy 210 – Gastric System 5 19:00 The reverse gradients of pressure are not created by anti-peristaltic waves or  contractile movement. The vomiting results from the action of the diaphragm and  abdominal muscles to increase intraabdominal pressure – GIT is mostly passive. How is it regulated? Regulation of these reflexes takes place in the vomiting  center, on the flour of the 4 th  ventricle. Taking it off, no vomiting will ever occur.  Impulses occur from anywhere in the body (distension, irritation of the GIT, UG,  pain, biochemical disequlibrium, psychogenic factors, unequal stimulation of  labyrinth, ie motion sickness for instance). The output, however, is fairly  stereotyped.  Widespread autonomic discharge + nausea, also retching o Dilated pupils, cutaneous BV constriction (pale skin), sweating, salivation,  o These precede and accompany the expulsion of contents.  o EMESIS : Results in the relaxation of the GI tract + spasm of the pyloric  antrum and duodenum, AND contraction of abdominal muscles and  diaphragm. The emetic response can be triggered by chemicals and/or bacteria. They don’t  act directly on the emetic response, however, because of the blood/brain barrier.  The CTZ, however, lies outside the bb barrier and can be stimulated by agents  such as drugs, chemicals and toxins. It can sense these agents and does not  induce vomiting directly, except by sending impulses to the fourth ventricle, then 
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This note was uploaded on 04/26/2011 for the course PHGY 210 taught by Professor Trippenbach during the Spring '08 term at McGill.

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Phgy 210 – Gastric System 5 -...

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