Which hormone is released by the presence of fat and protein in the small intestine and has a major effect in decreasing gastric emptying?
Both CCK and GIP inhibits gastric emptying, but CCK has a major effect. Hormone Site of secretion Control of secretion Major action Gastrin G-cells of gastric antrum Stimulated by 1. Distention of the stomach 2. Products of proteins digestion (paicularly phenylalanine and tryptophan) 3. Gastrin-releasing peptide (GRP, identical to amphibian's bombesin)Inhibited by:1. Acid in the antrum2. Somatostatin 1. Main action is gastric acid secretion 2. Stimulates gastric motility 3. Growth of gastric and intestinal mucosa (trophic action) Cholecystokinin I cells in the mucosa of duodenum and jejunum Stimulated by products of digestion especially fatty acids (most potent), peptides, and amino acids 1. Stimulates secretion of pancreatic juice rich in enzymes and bicarbonate 2. Contraction of gall bladder 3. Inhibits gastric emptying Secretin S cells of duodenum, jejunum and ileum Acid is the most potent stimulus for releaseAlso, products of protein digestion (Ganong) and Fat (Guyton) stimulates release 1. Stimulates secretion of HCO3- rich pancreatic juice and bile 2. Decreases gastric acid secretion and delays gastric emptying GIP K cells in duodenum and jejunum Stimulated by three major foodstuffs: fatty acids and amino acids and to a lesser extent carbohydrate 1. Gastric Inhibitory Peptide: in large doses it inhibits gastric secretion and motility 2. Glucose-dependent insulinotropic peptide: increases insulin release in response to oral glucose intake (incretin effect) 3. Delays gastric emptying VIP (vasoactive intestinal peptide) GIT nerves 1. Stimulates intestinal secretion of electrolytes and hence of water. Excess VIP may cause watery diarrhoea. 2. Relaxation of intestinal smooth muscle, including sphincters 3. Dilation of peripheral blood vessels. Excess secretion may cause decreased BP Motilin M cells in duodenum and jejunum 1. Produces contraction of smooth muscle in the stomach and intestines in the period between meals by initiating migrating motor complex
CCK
GIP
Gastrin
Motilin
GIT