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What is the mechanism of antiperistalsis that occurs during vomiting? Why the peristaltic waves normally don't propagate in anal to oral direction? Please give logical explanation with authentic sources. :)

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What is the mechanism of antiperistalsis that occurs during vomiting?

  1. Emetic agents in the bloodstream stimulate chemoreceptors in area postrema and nucleus tractus solitarius [1].
  2. Nucleus tractus solitarius is connected to motor neurons in ventral medulla and hypothalamus [1].
  3. Esophageal and gastric peristalsis is inhibited. Small bowel peristalsis is reversed. Esophagus and stomach don't have antiperistaltic movements [2].

Why the peristaltic waves normally don't propagate in anal to oral direction?

Because of the mechanism of descending inhibition. Distension of the esophagus and intestine causes a reflex action that leads to circular muscular contraction just above the bolus/chymus. Longitudinal muscle also contracts (shortens) [3].

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Reference:

  1. Hornby PJ. Central neurocircuitry associated with emesis. Am. J. Med. 2001 Dec 3;111 Suppl 8A:106S-112S. PubMed PMID: 11749934.

  2. Brizzee KR. Mechanics of vomiting: a minireview. Can. J. Physiol. Pharmacol. 1990 Feb;68(2):221-9. PubMed PMID: 2178746.

  3. AUMSA. Digestive Physiology. May 2012. CC-BY-SA-3.0

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