What role does glucagon play in the body?

Glucagon is a hormone produced by the alpha cells of the pancreas and plays a crucial role in regulating blood glucose levels, especially during fasting or between meals. Its primary function is to increase blood glucose levels when they fall too low. It does this by promoting glycogenolysis, which is the breakdown of glycogen into glucose, primarily in the liver. Additionally, glucagon stimulates gluconeogenesis, a metabolic pathway that results in the generation of glucose from non-carbohydrate substrates.

When glucagon is released into the bloodstream, it initiates these processes, thereby raising blood glucose levels to ensure that energy is available for cellular functions, particularly for the brain and muscles, which rely heavily on glucose. This makes glucagon an essential counter-regulatory hormone to insulin, which lowers blood glucose levels.

In the context of this question, the choice indicating that glucagon increases blood glucose levels correctly represents the hormone's vital physiological role in maintaining glucose homeostasis in the body.