Download L 3 Pancreatic hormones 25th september 2012

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
Pancreas and its secretions
- long, thin delicate organ
- pinkish gray, glandular
Secretions of pancreas
- Exocrine
- enzymes and carbonates
- Endocrine
- hormones
Pancreatic hormones
Hormones of the pancreas
- Insulin
- Glucagon
- Somatostatin
- Pancreatic peptides
- They are secreted by the specific cells located in the islets
scattered throughout thte pancreas
- polypeptides
Pancreas and its hormones
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
Insulin
Main functions
Fat Break down inhibited
Blood
Glucose
Amino
acids
uptake of
glucose
Insulin
uptake of
amino/a
Insulin
Muscle, Liver
(Stored as glycogen)
Used for protein
synthesis by all cells
- All essential amino/a (balanced ration) are needed
for protein synthesis
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
Glucagon
Opposite effect of insulin
Glycogen
Glycogenolysis
Fat
(Lipolysis)
glucagon
glucagon
glucose
glucose
Control of insulin and glucagon secretion – Glucose homeostasis
Normal blood glucose value of animals (mg/dl)
Horse
60-110
cow
40-80
sheep
40-80
Blood glucose level lower
than other animals
Pig
80-120
dog
70-120
chicken
130-270
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