SB7e- Control of blood glucose

• What is homeostasis?

  The regulation of conditions inside the body to maintain a stable internal environment, in response to both internal and external conditions
• What is the negative feedback mechanism?

  Used to respond to a change in conditions to help bring the condition back to normal
• When does the body use automatic control systems?

  When there is a change from optimal conditions, and a signal occurs to reverse the change back to normal status
• What does an automatic control system contain?

  1. Receptors (detect a change)
  2. Coordination centres (interpret the change and decides what to do about it, eg the brain/spine)
  3. Effectors (carries out change, eg muscles or glands. Muscles contract and glands release hormones)
• Why is a constant internal environment important?

  Enzymes will only function under a small range of conditions
• Blood glucose concentration if it rises too far from normal

  1. Blood glucose conc rises eg. after eating
  2. The pancreas detects this rise
  3. The pancreas secretes insulin and decreases the secretion of glucagon
  4. Insulin causes muscle and liver cells to remove glucose from blood and store it as glycogen
  5. Blood glucose conc returns back to normal
• Blood glucose concentration if it falls too low from normal

  1. Blood glucose conc falls eg. after exercise
  2. The pancreas detects the fall
  3. The pancreas decreases secretion of insulin and increases secretion of glucagon
  4. Glucagon causes the liver to convert glycogen into glucose and release it back into the blood
  5. Blood glucose conc returns back to normal
• A person who cannot control their blood glucose concentration has a condition called diabetes.
• Type 1 diabetes

  Cause- The immune system has damaged the person's insulin secreting pancreas cells, so the person only produces little or none insulin.

  Control- They have to work out the right amount of insulin and inject it into the fat below the skin, to keep the BGC in safe limits.