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Endocrine System
Lecture 3Pancreatic gland and its hormones
Asso. Professor Dr Than Kyaw24 September 2012
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The pancreas
Pancreas – both exocrine and endocrine functionsExocrine function
- associated with digestion- include digestive enzyme and bicarbonate secretions
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- long, thin delicate organ - pinkish gray, glandular
Secretions of pancreas- Exocrine
- enzymes and carbonates
- Endocrine- hormones
Pancreas and its secretions
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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
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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
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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
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Pancreas and its hormones
- Generally insulin promotes- Fat deposition- Protein synthesis
- The result of insulin activity - lowering blood glucose level
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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
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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
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GlycogenGlycogenolysis glucose
glucagon
Glucagon
Opposite effect of insulin
Fat (Lipolysis) glucose
glucagon
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Control of insulin and glucagon secretion – Glucose homeostasis
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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
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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
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Pancreatic polypeptide
• The secretion of pancreatic polypeptide - stimulated - by ingestion of protein- by fasting
- No definite function has been established
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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
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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
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End of Lecture