Endocrine System Lecture 3 Pancreatic gland and its hormones Asso. Professor Dr Than Kyaw 24 September 2012

The pancreas Pancreas – both exocrine and endocrine functions Exocrine function - associated with digestion - include digestive enzyme and bicarbonate secretions

- long, thin delicate organ - pinkish gray, glandular Secretions of pancreas - Exocrine - enzymes and carbonates - Endocrine - hormones Pancreas and its secretions

Pancreatic hormones - They are secreted by the specific cells located in the islets scattered throughout thte pancreas - polypeptides Hormones of the pancreas - Insulin - Glucagon - Somatostatin - Pancreatic peptides

Endocrine - islets of Langerhans 4 types of cells - insulin ( beta cells) - glucagon (alpha cells) - somatostatin (delta cells) - pancreatic peptides (F cells) Pancreas and its hormones

Insulin sensitivity - Liver, muscle, adipose tissue and leukocytes - rapid response - Brain, kidney, intestine and erythrocytes - little or no response - Principle effect on sensitive tissues which allow the transport of glucose across the cell membrane - Insulin enhances facilitated diffusion -Liver – insulin enhances glucose uptake - by stimulating enzymes that assist production of glycogen and lipogenesis - by inhibiting enzymes that catalyze glycogenolysis Pancreas and its hormones

-Generally insulin promotes -Fat deposition -Protein synthesis - The result of insulin activity - lowering blood glucose level

Blood Glucose uptake of glucose Muscle, Liver (Stored as glycogen) Insulin Amino acids uptake of amino/a Used for protein synthesis by all cells Insulin - All essential amino/a (balanced ration) are needed for protein synthesis Insulin Main functions Fat Break down inhibited

Glucagon The result of glucagon activity - elevation of blood glucose concentration This is achieved by activation of adenylcyclase in liver cells. It in turn stimulate s phosphorylase -- result in glycogenolysis. Glucagon also - increases gluconeogenesis - increases metabolic rate - stimulate lipolysis

Glycogen Glycogenolysis glucose glucagon Glucagon Opposite effect of insulin Fat (Lipolysis) glucose glucagon

Control of insulin and glucagon secretion – Glucose homeostasis

Normal blood glucose value of animals (mg/dl) HorsecowsheepPigdogchicken Blood glucose level lower than other animals

Somatostatin Inhibitory agent - slow the output of nutrients into the circulation To moderate the metabolic effects of insulin, glucagon and growth hormone i.e., somatostatin inhibit s secretion of insulin and glucagon Also as a moderator it inhibits the secretion of cholecystokinin, pancreatic exocrine secretion and gastric acid Somatostatin also moderates gastroinstestinal motility and absorption of glucose

Pancreatic polypeptide The secretion of pancreatic polypeptide - stimulated - by ingestion of protein - by fasting - No definite function has been established

Control of insulin and glucagon secretion The secretion of insulin and glucagon - controlled directly by the blood glucose concentration Because of dual control of these two hormones - blood glucose level show little variation Important stimulatory effects of insulin on the secretion of - gastrointestinal hormone, gastrin, secretin, cholecystokinin, and other hormones, Gastrointestinal hormones are secreted in response to food ingestion – cause insulin to be secreted before glucose absorption

Control of insulin and glucagon secretion Glucagon secretion - stimulated by hypoglycemia, stress - inhibited by glucose, secretin, insulin, and somatostatin Somatostatin secretion - enhanced by almost every factors that increases insulin secretion

End of Lecture