Regulating Blood Glucose Concentration (Edexcel GCSE Biology)

• Blood glucose concentration must be kept within a narrow range, so it’s another example of homeostasis (like temperature control)
• Blood glucose concentration is monitored and controlled by the pancreas
• The pancreas is an endocrine gland (making and secreting hormones into the bloodstream) and it also plays a vital (but separate) role in digestion (making and secreting enzymes into the digestive system)
• Eating foods containing carbohydrate results in an increase of glucose into the bloodstream
• If the blood glucose concentration is too high, the pancreas produces the hormone insulin to bring it back down
  • Too high a level of glucose in the blood can lead to cells of the body losing water by osmosis, which can be dangerous

• Insulin stimulates cells to take in glucose from the bloodstream (particularly liver and muscle cells)
• In liver and muscle cells excess glucose is converted into glycogen (a polymer of glucose) for storage

• If the blood glucose concentration is too low, the pancreas produces the hormone glucagon that causes glycogen to be converted into glucose and released into the blood.
• Glucagon and insulin interact as part of a negative feedback cycle to control blood glucose (sugar) levels in the body:
  • Insulin is produced when blood glucose rises and stimulates liver and muscle cells to convert excess glucose into glycogen to be stored – this reduces the blood glucose level
  • Glucagon is produced when blood glucose falls too low and stimulates liver and muscle cells to convert stored glycogen into glucose to be released into the bloodstream – this increases the blood glucose level

Negative feedback regulation of blood glucose levels