What is the effect of glucagon on blood glucose levels?

Glucagon plays a critical role in regulating blood glucose levels, particularly during fasting or periods of low carbohydrate intake. Its primary function is to increase blood glucose levels when they drop too low. This is achieved through two main processes: glycogenolysis and gluconeogenesis.

Glycogenolysis refers to the breakdown of glycogen, which is stored primarily in the liver, into glucose. When glucagon is released from the alpha cells of the pancreas, it binds to its receptors on liver cells, triggering the mobilization of glucose from glycogen reserves.

Gluconeogenesis, on the other hand, is the process by which the liver generates glucose from non-carbohydrate precursors, such as amino acids and glycerol, particularly when glycogen stores are depleted.

The combined effect of these two processes—glycogenolysis and gluconeogenesis—results in an increase in glucose levels in the bloodstream, making glucagon a vital hormone for maintaining glucose homeostasis, especially during times of metabolic need. This is why the correct answer notes that glucagon increases blood glucose levels.