Regulation of insulin levels

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  • Insulin regulation
    • Control of insulin secretion:
      • 1. The cell membrane has potassium and calcium ion channels.
      • 2. Potassium ion channels are normally open so potassium ions flow out.
      • 3. When blood glucose concentration is high, the glucose moves into the cell.
      • 4. Glucose is metabolised to produce ATP.
      • 5. The ATP closes the potassium ion channels.
      • 6. Accumulation of K+ ions alters potential difference across cell membrane - inside becomes less negative.
      • 7. Change in potential difference opens the calcium ion channels.
      • 8. Calcium ions cause vesicles of insulin to fuse with the cell membrane, releasing insulin by exocytosis.
    • Diabetes mellitus:
      • Disease where the body is no longer able to control its blood glucose concentration.
      • Inability of cells to take up glucose from the blood. Can cause glucose to be excreted in the urine.
      • May arise when the pancreatic beta cells fail to produce insulin or when insulin receptors become abnormal.
    • Type 1 diabetes:
      • (Juvenile-onset diabetes) caused by an autoimmune response where the body's own immune system attacks Beta cells and destroys them.  Could also be caused by a viral infection.
    • Type 2 diabetes:
      • Non-insulin dependent. Insulin levels may be normal or reduced but the target cells fail to respond to the hormone due to receptor abnormalities.
      • Factors that bring about earlier onset. These include: Obesity, a diet high in sugar, being of Asian or Afro-Caribbean origin, family history.
    • Treatment for diabetes:
      • Type 1: Insulin injections. Blood glucose concentration must be monitored and correct dose of insulin must be given to ensure glucose conc remains stable.
      • Type 2: Careful monitoring and control of the diet. Matched with carbohydrate intake and use.
        • May be eventually supplemented with insulin injections or drugs which slow down absorption of glucose from the digestive system.
    • Glucose tolerance test:
      • Involves fasting for 8 hours. Blood test to determine fasting glucose conc.
        • Ingestion of glucose. Blood tests to monitor glucose conc at intervals over 2 and a half hours. Results are graphed.


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