PHGY 210 Lecture Notes - Lecture 20: Peristalsis, Chemoreceptor Trigger Zone, Retching
25 Feb 2013
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Document Summary
Vomiting: no anti-peristaltic waves in the upper tracks. Decrease resistance to upward flow and increase pressure in the stomach. The distal stomach (including sphincter) goes into spasm, this forces food up. The proximal stomach and esophagus are completely passive, no movement. The increase in the pressure is due to the descent of the diaphragm and the contraction of the stomach. Vomiting is then a result of the diaphragm and the abdominal muscles to increase inner pressure while the git is mostly passive. Regulation of vomiting: pharyngeal stimulation, distension/irritation, cardiac ischemia, pain, motion sickness, psychogenic factors and even biochemistry of ingested items could trigger vomiting. The afferent impulses go to the medulla vomiting centre. No vomiting without afferent going and efferent leaving the medulla. Tachycardia, then bradycardia, clammy hands due to vasoconstriction, this all leads to nausea, which then leads to small amount of retching. This is because the constrictions are not synchronized.
