Final answer:
Glucagon is a hormone that raises blood glucose levels by stimulating liver glycogen breakdown (glycogenolysis) and glucose synthesis (gluconeogenesis). Epinephrine, released during stress, also stimulates glycogenolysis. Corticotropin (ACTH) triggers the release of cortisol, which affects glucose metabolism and can have a glucose-sparing effect.
Step-by-step explanation:
Action of Hormones: Glucagon, Epinephrine, and Corticotropin
When blood glucose levels drop, the hormone glucagon is secreted by the alpha cells of the islets of Langerhans in the pancreas. Glucagon stimulates the liver to convert stored glycogen into glucose, which is then released into the bloodstream. This process is known as glycogenolysis. In addition, glucagon also supports the generation of glucose from non-carbohydrate sources in a process called gluconeogenesis, which occurs in the liver using amino acids and other substrates.
During stressful situations, epinephrine is released from the adrenal medulla and also stimulates glycogenolysis, particularly in muscle tissue. Rising blood glucose levels that result from the action of these hormones cause a negative feedback loop that inhibits further glucagon production.
Corticotropin (or ACTH) stimulates the release of cortisol from the adrenal cortex. Cortisol is a glucocorticoid that plays a vital role in glucose metabolism and can have a glucose-sparing effect in which the body utilizes fatty acids instead of glucose as an energy source, helping to maintain blood glucose levels during prolonged periods of stress or fasting.