Insulin

• Nervous system


  Method of communication
• Hormones


  Chemicals in blood, usually slow-acting
• Insulin


  A hormone that lowers blood glucose concentrations
• Insulin action


  1. Pancreas monitors blood glucose concentrations and produces insulin in response to increasing blood glucose concentrations

  2. Causes the liver and muscle cells to absorb more glucose from the blood, where it is used for respiration

  3. Some of the absorbed glucose is converted to glycogen in the liver for storage
• It is important that the amount of glucose (sugar) in the blood is kept at the optimum concentration
• Meal containing carbohydrate


  Blood glucose level rises
• Blood glucose level rises


  Blood glucose level returns to normal
• Insulin is a chemical messenger, produced by the pancreas (a gland) that travels in the blood to bring about a response in the liver and/or muscles (target organs)
• Exam tips

  • In an exam you need to state that insulin lowers/reduces blood glucose concentrations - it is not enough to say that it controls blood glucose concentrations
• Example 1


  • Explain why the body needs glucose in the blood
• Example 2


  • Suggest why the concentration of insulin in the blood is usually at its lowest in the middle of the night
• The glucose is transported to body cells to provide energy in respiration
• Glucose concentrations will also be low during the night. By this time the glucose from the last meal of the day has been used up in respiration or converted to glycogen for storage
• Negative feedback


  A mechanism to ensure that the concentration of something, such as blood glucose concentration, does not deviate too far from the normal value
• As blood sugar concentration increases


  The rate of insulin production also increases to reduce blood glucose concentration
• As blood glucose level falls as a result of insulin action


  The amount of insulin produced is reduced