The pancreas monitors the concentration of glucose in the blood using the hormones insulin and glucagon.
Insulin is a hormone produced in the pancreas that causes cells to take up glucose and stimulates liver and muscle cells to convert glucose to glycogen (a polymer of glucose) for storage.
Glucagon is a hormone produced in the pancreas that stimulates liver and muscle cells to break down glycogen into glucose and release it back into the bloodstream.
The diagram below shows this negative feedback cycle and the relationship between insulin and glucagon.
Blood glucose concentration must be kept within an ideal range, so this is an example of homeostasis.
When blood glucose levels are too low:
1. The pancreas releases glucagon into the bloodstream
2. Glucagon stimulates glycogen breakdown in the liver, converting it into glucose
3. This increases the concentration of glucose in the blood back to normal levels
When the blood glucose levels are too high:
1. The pancreas releases insulin into the bloodstream
2. Insulin stimulates the liver to convert glucose into glycogen and it causes cells to take up glucose
3. This decreases the concentration of glucose back to normal levels