Glucagon

Definition

Glucagon is a hormone produced by the alpha cells of the pancreas that plays a crucial role in glucose metabolism by raising blood glucose levels. It works oppositely to insulin, stimulating the liver to convert stored glycogen into glucose and release it into the bloodstream, thus maintaining energy homeostasis. Glucagon's function is especially vital during fasting or low-carbohydrate intake when the body needs to increase available glucose for energy.

5 Must Know Facts For Your Next Test

1. Glucagon is secreted in response to low blood sugar levels, such as during fasting or intense exercise.
2. It promotes glycogenolysis and gluconeogenesis in the liver, ensuring a steady supply of glucose during times of need.
3. Glucagon also influences fat metabolism by promoting lipolysis, which helps release fatty acids for energy production.
4. Patients with diabetes may require glucagon injections in emergencies to treat severe hypoglycemia when they cannot consume carbohydrates orally.
5. The balance between glucagon and insulin is critical for maintaining normal glucose levels, as their actions are inversely related.

Review Questions

• How does glucagon interact with insulin in the regulation of blood glucose levels?
  • Glucagon and insulin work together to maintain blood glucose levels within a narrow range. While insulin lowers blood glucose by facilitating its uptake into cells and promoting storage as glycogen, glucagon raises blood glucose by stimulating the liver to convert glycogen back into glucose and release it into the bloodstream. This counter-regulatory action ensures that the body has a balanced supply of glucose depending on its metabolic needs.
• What are the physiological effects of glucagon during fasting, and why are these effects important for energy homeostasis?
  • During fasting, glucagon levels rise to prevent hypoglycemia by promoting glycogenolysis and gluconeogenesis in the liver. These processes increase the availability of glucose, ensuring that vital organs like the brain have a continuous supply of energy despite limited food intake. This mechanism is essential for maintaining energy homeostasis, allowing the body to function optimally even when external sources of glucose are not available.
• Evaluate how dysregulation of glucagon secretion can contribute to metabolic disorders such as diabetes mellitus.
  • Dysregulation of glucagon secretion can lead to significant issues in metabolic disorders like diabetes mellitus. In type 1 diabetes, insufficient insulin production can cause unchecked glucagon release, leading to hyperglycemia due to excessive gluconeogenesis and glycogenolysis. In type 2 diabetes, insulin resistance can impair the normal feedback inhibition on glucagon secretion, resulting in elevated glucagon levels that exacerbate high blood sugar. This imbalance between insulin and glucagon creates challenges in managing blood glucose levels effectively.

Related terms

Insulin:

A hormone produced by the beta cells of the pancreas that lowers blood glucose levels by facilitating cellular uptake of glucose and promoting glycogen storage.

Glycogenolysis: The biochemical process of breaking down glycogen into glucose, which glucagon stimulates primarily in the liver.

Hypoglycemia:

A condition characterized by abnormally low blood glucose levels, which glucagon helps to counteract by increasing glucose availability.