06 Gut Hormones

06 Gut Hormones - Gut Hormones HNFE 3025 Fall 2009 Gastrin...

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Gut Hormones HNFE 3025 Fall 2009
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Gastrin Gastrin is a mixture of several peptides, of which the most active contains 14 amino acids. 2 isoforms – Gastrin I, Gastrin II 17 amino acids (minimum of 4 needed for activity) It is secreted by cells in the stomach and duodenum It stimulates the exocrine cells of the stomach to secrete gastric juice , a mixture of hydrochloric acid and the proteolytic pro- enzyme pepsinogen. 2
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Somatostatin This mixture of peptides is secreted by cells in the gastric glands of the stomach and acts on the stomach (thus a paracrine effect) where it inhibits the release of gastrin and hydrochloric acid; and in the duodenum where it inhibits the release of secretin and cholecystokinin to be discussed; and the pancreas where it inhibits the release of glucagon . Taken together, all of these actions lead to a reduction in the rate at which nutrients are absorbed from the contents of the intestine. Somatostatin is also secreted by the hypothalamus and the pancreas . 3
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Secretin It is a polypeptide of 27 amino acids. It is secreted by cells in the duodenum when they are exposed to the acidic contents of the emptying stomach. It stimulates the exocrine portion of the pancreas to secrete bicarbonate into the pancreatic fluid (thus neutralizing the acidity of the intestinal contents). 4
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A mixture of peptides, of which an octapeptide (8 amino acids) is the most active. 33 amino acids (minimum of 7 needed for activity) It is secreted by cells in the duodenum and jejunum when they are exposed to food. It acts on the gall bladder stimulating it to contract and force its contents of bile into the intestine and; on the pancreas stimulating the release of pancreatic digestive enzymes into the pancreatic fluid. CCK also acts on vagal neurons leading back to the medulla oblongata which give a satiety signal (i.e., "that's enough food for now"). 5
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This note was uploaded on 03/23/2010 for the course HNFE 3025 taught by Professor Mwhulver during the Spring '10 term at Virginia Tech.

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06 Gut Hormones - Gut Hormones HNFE 3025 Fall 2009 Gastrin...

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