6.4.4 Glucagon

How Glucagon Works

1. Detection of Low Glucose:

• A drop in blood glucose concentration is detected by alpha cells in the pancreas.

2. Secretion of Glucagon:

• Alpha cells secrete glucagon, which inhibits the action of beta cells (which release insulin).

3. Target Cells:

• Glucagon primarily acts on hepatocytes (liver cells).

Effects of Glucagon:

1. Glycogenolysis:

• Glucagon stimulates the breakdown of glycogen into glucose in liver cells.

2. Gluconeogenesis:

• Glucagon stimulates the conversion of non-carbohydrate molecules (e.g. fatty acids, amino acids) into glucose.

3. Glucose Release:

• The newly produced glucose diffuses out of hepatocytes into the bloodstream, increasing blood glucose levels.

4. Switch to Fatty Acid Use:

• In the absence of sufficient glucose, other cells begin using fatty acids or amino acids for respiration instead.

Summary of Glucagon's Role in Increasing Blood Glucose Levels:

• Promotes glycogenolysis (breakdown of glycogen).
• Stimulates gluconeogenesis (formation of glucose).
• Encourages glucose release from hepatocytes into the blood.
• Reduces glucose use by promoting the use of fatty acids and amino acids in respiration.