blood glucose level - negative feedback

• what is the role of beta cells?


  secrete insulin into the blood
• what is the role of alpha cells?


  secrete glucagon into the blood
• where are both cells secreted in the pancreas?


  cluster of cells called islets of langerhans
• what is the role of insulin in controlling blood glucose concentration?

  it lowers the blood glucose concentration
• what does insulin do in lowering the blood glucose level?


  binds to specific receptors - on liver + muscle cells

  increases the membrane permeability to glucose, so cells take up more glucose.

  activates glycogenesis

  cells respire more glucose
• what is the role of glucagon in control blood glucose level?


  it raises the blood glucose level
• what does glucagon do in raising the blood glucose level?


  binds to specific receptors - on liver cells

  activates glycogenolysis

  activates gluconeogenesis

  cells respire less glucose
• how do beta cells secrete insulin when they detect high blood glucose concentration?


  more glucose enters Beta cells by facilitated diffusion

  increases in rate of respiration - more ATP

  this triggers sodium potassium channels to close

  means potassium ions cant exit - build up inside

  inside becomes less negative - depolarised

  triggers calcium channels to open - calcium diffuse in

  vesicles fuse with membrane - insulin released (exocytosis)