Cephalic Phase - Digestive System Cephalic Phase Vagal...

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Digestive System Cephalic Phase * Vagal reflexes initiated during the cephalic phase also (5) stimulate acid secretion by parietal cells in the stomach. * These "long" reflexes, acting through cholinergic neurons of the enteric nerve plexus stimulate, * secretion of HCl by parietal cells * secretion of histamine by the enteroendocrine (enterochromaffin-like, ECL) cells. Cephalic Phase * Histamine in turn stimulates parietal cell secretion of acid . * In addition, vagal reflexes to the antrum stimulate secretion of the hormone gastrin from G cells. * Elevated levels of circulating gastrin increase acid secretion by * direct stimulation of parietal cells and * by stimulating histamine secretion from ECL cells. * Vagal reflexes also induce a relatively small (6) stimulation of enzyme secretion by the exocrine pancreas. Gastric Phase * Begins when food enters the stomach. * Distention ( ) of the stomach activates stretch receptors initiating a number of reflexes (1-7) which alter gastric, intestinal, colonic and pancreatic activities. * Gastric acid secretion is stimulated by
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Cephalic Phase - Digestive System Cephalic Phase Vagal...

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