Final answer:
Beta cells in the pancreas do not release insulin when blood glucose levels are low; instead, alpha cells release glucagon to raise glucose levels. Insulin is secreted in response to high blood glucose levels to facilitate its uptake by cells.
Step-by-step explanation:
When glucose levels are low, beta cells in the pancreas do not release insulin. Instead, alpha cells are stimulated to secrete the hormone glucagon into the bloodstream. Glucagon then promotes the breakdown of glycogen into glucose by the liver and stimulates the production of glucose from amino acids and glycerol. This process increases the blood glucose concentration back to the normal range, maintaining homeostatic balance. It's important to note that insulin is released in response to high glucose levels, not low.
Homeostatic imbalance and disease can result when these regulatory mechanisms do not function properly, such as in diabetes mellitus, where there is target cell resistance to insulin, leading to consistently high blood glucose levels.