Final answer:
Glucagon, released from the pancreas when blood glucose levels are low, stimulates the liver to release glucose through processes like glycogenolysis and gluconeogenesis, thus increasing blood glucose levels.
Step-by-step explanation:
Glucagon promotes the release of glucose from the liver. When blood glucose levels decrease, such as during fasting or intense exercise, the hormone glucagon is released by the alpha cells of the islets of Langerhans in the pancreas. Glucagon has multiple effects that contribute to the increase of blood glucose levels: it stimulates glycogenolysis, the breakdown of glycogen into glucose within liver cells; promotes gluconeogenesis, the synthesis of glucose from non-carbohydrate sources like amino acids and glycerol; and encourages the mobilization of fatty acids from fat tissue.
The actions of glucagon are crucial for maintaining energy homeostasis in the body, especially during periods when glucose levels are low. These mechanisms work in tandem to ensure that blood glucose concentrations remain within a normal, healthy range.