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The Endocrine Pancreas

The Endocrine Pancreas. Lecture Objectives:. what are the different cell types and what do they secrete? what is the balance between insulin and glucagon? what does insulin do? what is Diabetes Mellitus?. The Pancreas. 98% of pancreas is dedicated to exocrine secretion

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The Endocrine Pancreas

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  1. The Endocrine Pancreas Lecture Objectives: • what are the different cell types and what do they secrete? • what is the balance between insulin and glucagon? • what does insulin do? • what is Diabetes Mellitus?

  2. The Pancreas • 98% of pancreas is dedicated to exocrine secretion • 2% of pancreas is dedicated to endocrine secretion • islets of Langerhans • receive both sympathetic and parasympathetic innervation

  3. Islets of Langerhans • islets are spread throughout the pancreas • 4 cell types • alpha cells secrete glucagon (20%) • beta cells secrete insulin (75%) • delta cells secrete somatostatin (<5%) • F or PP cells secrete pancreatic polypeptide (rare)

  4. Balance Between Insulin and Glucagon

  5. Insulin • synthesized as proinsulin and converted to a polypeptide • sequence conserved between species - development of antibodies

  6. Physiological Actions of Insulin • increases uptake and storage of glucose • stimulates glycogenesis • inhibits lypolysis, promotes fat uptake and storage • increases protein synthesis

  7. Regulation of Insulin Secretion • primary determinant = plasma glucose level • increased plasma amino acids • release of gastrointestinal hormones (GIP) • parasympathetic stimulation - triphasic response

  8. Glucagon • small protein released from alpha cells • prevents hypoglycemia following high protein meal • helps mobilize glucose during exercise

  9. Physiological Actions of Glucagon • glycogenolysis • glyconeogenesis • lipolytic • ketogenic gluconeogenesis

  10. Regulation of Glucagon Secretion • increased by decreased plasma glucose • increased by elevated plasma amino acids • increased by exercise • pancreatic sympathetic stimulation

  11. Diabetes Mellitus • most common endocrine disorder • characterized by polyuria, polydipsia, weight loss despite polyphagia, hyperglycemia, glucosuria, ketosis, acidosis • primary cause = reduced entry of glucose into peripheral tissues

  12. Insulin Dependent Diabetes Mellitus (IDDM) • also called type I or juvenile onset • associated with ketosis and acidosis • pathological changes in beta cells • plasma insulin low or undetectable • treatment = insulin injection

  13. Insulin Shock • insulin excess causes hypoglycemia • lack of fuel (glucose) for brain results in coma • hypoglycemia normally triggers secretion of: • glucagon • epinephrine • cortisol • growth hormone

  14. Non-Insulin Dependent Diabetes Mellitus (NIDDM) • also called type II or adult onset • patients are generally obese • insulin levels can be normal • insulin receptors downregulated • treatment = diet, sulfonylureas

  15. Glucose Tolerance Test • administer a glucose challenge and monitor blood glucose levels • blood glucose rises higher and returns to baseline more slowly in diabetics

  16. Ketone Bodies and Acidosis acetyl-CoA acetoacetate acetone B-hydroxybutyrate • decreased pH • respiration changes • acidic urine • can lead to coma

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