Endocrine System Lecture 3 - PowerPoint Presentation

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Endocrine System

Lecture 3Pancreatic gland and its hormones

Asso

. Professor Dr Than

Kyaw

24 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 promotesFat depositionProtein synthesis- The result of insulin activity - lowering blood glucose level

Blood

Glucoseuptake 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 concentrationThis 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

Glycogenolysisglucose

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)

Horsecow

sheep

Pig

dog

chicken

60-110

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 hormonei.e., somatostatin inhibit s secretion of insulin and glucagonAlso 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 concentrationBecause 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