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. When blood sugar levels drop, glucagon stimulates the liver to convert stored glycogen into glucose, releasing it into the bloodstream to restore balance. This hormone is essential for maintaining homeostasis and ensuring that the body has enough energy between meals.

5 Must Know Facts For Your Next Test

1. Glucagon is secreted in response to low blood sugar levels, particularly during fasting or between meals.
2. The primary target organ for glucagon is the liver, where it promotes glycogenolysis and gluconeogenesis to increase blood glucose levels.
3. Glucagon works in opposition to insulin; when insulin decreases after eating, glucagon increases to balance glucose levels.
4. In addition to increasing blood glucose, glucagon also stimulates the breakdown of fats in adipose tissue for energy.
5. Excessive glucagon can lead to hyperglycemia, which is a condition characterized by elevated blood sugar levels.

Review Questions

• How does glucagon contribute to maintaining homeostasis in the body?
  • Glucagon plays a key role in maintaining homeostasis by regulating blood glucose levels. When blood sugar decreases, such as during fasting or prolonged exercise, glucagon is released from the pancreas. It signals the liver to convert stored glycogen into glucose and release it into the bloodstream, effectively raising blood sugar levels back to a normal range. This process ensures that the body has a consistent supply of energy for its vital functions.
• Describe the relationship between glucagon and insulin in glucose regulation.
  • Glucagon and insulin have a complementary relationship in regulating blood glucose levels. Insulin lowers blood sugar by facilitating glucose uptake into cells after meals, while glucagon increases blood sugar when levels are low. The balance between these two hormones ensures stable glucose levels; when insulin levels drop post-meal, glucagon rises to prevent hypoglycemia. This interplay is crucial for metabolic control and energy homeostasis.
• Evaluate the impact of glucagon on metabolic processes in response to fasting conditions.
  • During fasting conditions, glucagon significantly influences metabolic processes by promoting glycogenolysis and gluconeogenesis in the liver. When food intake stops, glucagon is secreted to maintain adequate blood glucose levels for energy. It stimulates the breakdown of glycogen into glucose and encourages the synthesis of new glucose from non-carbohydrate sources. This hormonal action prevents hypoglycemia, providing essential energy for organs like the brain that rely heavily on glucose.

Related terms

Insulin:

A hormone produced by the beta cells of the pancreas that lowers blood glucose levels by facilitating the uptake of glucose into tissues.

Glycogenolysis: The process by which glycogen is broken down into glucose in the liver and muscles, stimulated by glucagon during fasting or low-energy states.

Homeostasis:

The maintenance of stable internal conditions in the body, including blood glucose levels, temperature, and pH, despite external changes.