Glucagon

Definition

Glucagon is a peptide hormone produced by the alpha cells of the pancreas that plays a crucial role in regulating blood glucose levels, particularly during fasting or low glucose situations. It works to increase glucose availability in the bloodstream by promoting gluconeogenesis and glycogenolysis in the liver, which are essential processes in energy metabolism.

5 Must Know Facts For Your Next Test

1. Glucagon secretion is stimulated by low blood sugar levels and is inhibited by high blood sugar levels, illustrating its role in maintaining glucose homeostasis.
2. One key effect of glucagon is to stimulate the liver to convert stored glycogen into glucose, which increases blood sugar levels quickly during fasting or stress.
3. In addition to its role in increasing blood glucose levels, glucagon also promotes the breakdown of fatty acids in adipose tissue, providing energy during periods of low carbohydrate availability.
4. Glucagon works in opposition to insulin, making them key hormones in the regulation of metabolism and energy balance within the body.
5. The overall effects of glucagon are critical for survival during fasting or intense exercise, ensuring that the body has sufficient glucose and energy substrates when needed.

Review Questions

• How does glucagon regulate blood sugar levels during fasting?
  • During fasting, glucagon is secreted in response to low blood sugar levels. It acts primarily on the liver to stimulate glycogenolysis and gluconeogenesis, leading to an increase in glucose production and release into the bloodstream. This action helps maintain adequate blood sugar levels, ensuring that vital organs and tissues have a continuous supply of energy during periods without food intake.
• Discuss how glucagon interacts with insulin in maintaining metabolic homeostasis.
  • Glucagon and insulin are antagonistic hormones that work together to maintain metabolic homeostasis. While glucagon increases blood glucose levels by promoting gluconeogenesis and glycogenolysis, insulin lowers blood glucose by facilitating cellular uptake and storage as glycogen. The balance between these two hormones is crucial; when blood sugar rises after a meal, insulin is secreted to lower it, while during fasting or low energy states, glucagon is released to raise blood sugar levels back to normal.
• Evaluate the role of glucagon in energy metabolism under physiological stress conditions.
  • Under physiological stress conditions such as intense exercise or illness, glucagon plays a critical role in energy metabolism by ensuring that sufficient glucose is available for tissues that rely on it for fuel. Stress activates the sympathetic nervous system, leading to increased glucagon secretion which promotes gluconeogenesis and glycogenolysis. This process not only raises blood sugar levels but also enhances lipolysis, releasing fatty acids into circulation for additional energy. The ability of glucagon to mobilize energy reserves rapidly is essential for supporting metabolic demands during stressful situations.

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 its storage as glycogen.

Glycogenolysis: The biochemical process of breaking down glycogen into glucose-1-phosphate, which can then be converted to glucose and released into the bloodstream.

Gluconeogenesis: The metabolic pathway that generates glucose from non-carbohydrate substrates, such as amino acids and glycerol, primarily occurring in the liver.