HTHSCI 2H03 Lecture Notes - Lecture 22: Peritoneum, Alkalosis, Chemoreceptor Trigger Zone
2 May 2016
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Document Summary
Nausea: an unpleasant and difficult to describe psychic experience often associated with: decreased gastric motility. Increased small intestinal tone; and: reverse proximal small intestine peristalsis. Vomiting: forceful expulsion/propulsion of stomach contents and the content of the proximal small intestine up to and out of the mouth. Vomiting can sometimes be maladaptive: e. g. when the body perceives medications as toxins and thinks that throwing up will help to expel them (even when they are sometimes administered iv) Vomiting can be advantageous for pathogens (microorganisms): vomiting aerosolizes pathogens and increases transmission. There are two anatomically and functionally distinct units that control vomiting. Visceral afferents from the gi tract: vagus or sympathic nerves; gi distension (very potent); mucosal irritation. Visceral afferents from outside the gi tract: bile ducts; peritoneum; heart and a variety of other organs. Detects chemical abnormalities (e. g. emetic drugs, hypoxia, diabetic ketoacidosis) Sends excitatory signals to vomiting center: many antiemetic drugs act at the level of the ctz.
