Homeostasis & Insulin (Cambridge (CIE) IGCSE Biology): Revision Note

Role of insulin in homeostasis

• Homeostasis is defined as the maintenance of a constant internal environment

• Homeostasis ensures that internal conditions within the body (such as temperature, blood pressure, water concentration, glucose concentration etc) are kept within set limits in order to ensure that reactions in body cells can function

The role of insulin

• Insulin is secreted into the blood at times when blood glucose levels are high; this is (most often) directly after a meal

• Insulin decreases blood glucose concentration by signalling to liver and muscle cells to take up excess glucose from the blood and convert it into glycogen for storage

• The kidneys can only cope with a certain level of glucose in the blood; if the level gets too high, glucose gets excreted and is lost in the urine

  • This is like running a car with a hole in the petrol tank; valuable fuel is being wasted

• Several hours later, when blood glucose levels have dipped due to respiration in body tissues, glycogen stores are converted back into glucose (triggered by the hormone glucagon) to help restore normal blood glucose levels