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GIT HORMONES Lecture Physiology Dr. Mujeeb Ahmed Shaikh Dr.Mohammed Sharique Ahmed Quadri 1 2. OVERVIEW OF GASTRO-INTESTINAL HORMONES • - We will discuss the following hormones: Gastrin Secretin CCK Motilin Somatostatin GIP VIP 2 GASTRIN • Produced by G-cells in the stomach. • Stimulates the release of HCL and Pepsinogen in the stomach. • Increases gastric motility. • Increases ileal motility . • Relaxes Ileocecal Sphincter. • Induces mass movements in colon [because to help the contents moving through GIT on arrival of new meal in the stomach]. 3 SECRETIN • Secretin is released from small intestine when stomach acid contents come to duodenum. Functions • It inhibits gastric emptying to delay the acid contents of stomach to enter in the duodenum. • It inhibits gastric secretion. • It acts on pancreatic duct to produce large volume of watery, NaHCO3 secretion. • It stimulates the secretion of NaHCO3 rich bile in the liver by acting on the bile ducts. 4 CCK [Cholecystokinin] • CCK is released from the duodenum in response mainly to fat, to a lesser extent to protein products. • Actions of CCK I. Inhibition of gastric motility and secretion II. Stimulates pancreatic Acinar cells to secrete pancreatic enzymes [amylase, lipase, Trypsinogen, Chymotrypsinogen]. III. It causes contraction of gall-bladder and relaxation of sphincter of Oddi. IV. Regulator of food intake (key role in satiety) 5 MOTILIN • It is polypeptide and secreted by entrochromaffin cells and Mo cells in the stomach, small intestine and colon. • It causes contraction of smooth muscles in the stomach and intestine. • It level increases during inter-digestive state and controls GIT motility between the meals. 6 SOMATOSTATIN • It is secreted by D-Cells in pancreatic islets and by similar D-cells in GIT mucosa. • Somatostatin inhibits secretion of Gastrin, VIP, GIP, Secretin and Motilin. • Somatostatin secretion is stimulated by acid in the lumen of intestine. • It acts probably in a paracrine fashion. 7 GIP [Glucose Dependent Insulinotorphic Peptide] • GIP is released from the duodenum. • GIP stimulates release of insulin. – Stimulated by presence of meal specially glucose GIP stimulates insulin release . • Inhibits gastric motility – before it was called Gastric Inhibitory Peptide [this role is minimum]. 8 VIP [Vasoactive Intestinal Peptide] • VIP is found in nerves in the GIT. • It stimulates intestinal secretion of electrolytes and water. • Other action – relaxation of intestinal smooth muscle including sphincters. • Inhibition of gastric acid secretion. • It potentiates the action of acetylcholine in salivary glands. • VIP is also found in brain, blood, autonomic nerves. 9 10 REMINDER REGARDING GIT ENZYMES 11 Thank you 12 References • Human physiology by Lauralee Sherwood, seventh edition • Text book physiology by Guyton &Hall,11th edition • Text book of physiology by Linda .s contanzo,third edition 13