Week Two Summer 2010 Short Course: Food and Science: Anatomy and Physiology: "FOOD AND SCIENCE SCHEDULE AND ASSIGNMENTS Barbara E. Goodman, Ph.D. (barb.goodman@usd.edu or 605-677-5158) July 12-16, 2010 Tuesday Ju 13 H..."
1. The four true hormones in the GI tract are gastrin, cholecystokinin, secretin, and gastric inhibitory peptide (GIP).
Gastrin is produced by endocrine cells in the stomach and upper part of the small intestine. It stimulates acid secretion by parietal cells in the stomach, stimulates pepsinogen secretion by chief cells in stomach, stimulates pancreas, bile, gallbladder, intestine. Gastrin is released by protein, distension, via the vagus nerve and is inhibited by acid in the stomach.
Cholecystokinin is produced by endocrine cells in small intestine. Cholecystokinin stimulates pancreatic enzymes and bicarbonate secretion, stimulates gallbladder contraction and release of bile into small intestine, inhibits gastric emptying due to byproducts of fats or proteins in small intestine and also inhibits gastric acid secretion.
Secretin is produced by endocrine cells in the small intestine. It stimulates pancreatic secretion of bicarbonate and water, is released by acid in small intestine, inhibits gastric emptying and secretion of acid and increases biliary secretion of bicarbonate and water.
Gastric inhibitory peptide is produced by endocrine cells in the small intestine. It stimulates insulin release fron the b cells of pancreas, is released by mostly fat and partly carbohydrates in small intestine, and inhibit's the release of HCl from parietal cells of stomach.
2. Neuromuscular reflexes in the GI tract are stimulated by the vagus nerve. They are controlled by the movement of neurotransmitters like acetylcholine that stimulate GI contractions an d peristalsis. The reflexes can also be triggered by hormones mentioned above which can take longer but have longer lasting effects.
see also response to Jeff.
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