endocrine system

Endocrine System

Lecture 3Pancreatic gland and its hormones

Asso. Professor Dr Than Kyaw24 September 2012

The pancreas

Pancreas – both exocrine and endocrine functionsExocrine 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

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 cellsInsulin- 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

GlycogenGlycogenolysis 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)

Horse cow sheep Pig dog chicken60-110 40-80 40-80 80-120 70-120 130-270

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