the pancreas and glucose regulation

• Islets of langerhans -

  • endocrine
  • alpha and beta cells
  • different stains needed to identify them

  Pancreatic acini -

  • Exocrine
  • produce digestive enzymes

  
• Alpha cells:

  •Produce and secrete glucagon

  Beta cells:

  •Produce and secrete insulin
• what might lead to an increase in glucose levels?

  • Consuming carbohydrates
  • Glycogenolysis – Glycogen stored in liver/muscles is broken down into glucose
  • Gluconeogenesis – Glucose produced from non- carbohydrate sources e.g. lipids or amino acids
• what might lead to a decrease in glucose levels?

  • Respiration (exercise)
  • Glycogenesis – Glucose is made into glycogen
• If glucose rises insulin is released from the B cells in the Islets of Langerhans

  All cells (except RBC) have receptors for insulin
• To decrease glucose

  • Glucose channels in cell membrane open
  • Increase uptake of glucose into cells
  • Increase respiration
  • Increase glycogenesis
  • Increase glucose to fat conversion
  • Inhibit glucagon release
• Insulin is broken down by enzymes in the liver and so need to be constantly released to have an effect
• Glucagon is released from the a cells in the Islets of Langerhans when Glucose is gone (Or drops). Only liver cells have receptors for glucagon
•  To increase glucose

  • Increase glycogenolysis
  • Reduce glucose absorbed into liver
  • Increase Gluconeogenesis
• When sugar levels return to normal this stops a cells releasing glucagon
• During normal glucose levels

  • Potassium changes are open
  • Calcium channels are closed
  • Meaning the beta cells have a 70mV charge compared with outside
• 1. Glucose levels rise
  2. Glucose enters glucose transporter
  3. Glucose is used to produce ATP
  4. ATP binds to potassium channels
  5. This causes them to close (They are ATP sensitive)
  6. Potassium can no longer move out so difference reduces to -30mV (Depolarisation occurs)
  7. Depolarisation causes voltage- gated calcium channels to open
  8. Calcium ions enter the cell and cause secretory vesicles to release insulin