Glucagon acts on which tissues to promote glucose release?

Glucagon acts on which tissues to promote glucose release?

• A. Brain and spinal cord
• B. Muscle tissue only
• C. Liver and adipose tissue
• D. Bone marrow

Answer: (C)

Glucagon raises blood glucose mainly by signaling the liver. When it binds to receptors on liver cells, it raises cAMP levels, activating enzymes that break down glycogen and promote gluconeogenesis, so glucose is released into the bloodstream. Adipose tissue also responds to glucagon by activating lipolysis, releasing glycerol and fatty acids; glycerol can travel to the liver and serve as a substrate for gluconeogenesis, helping generate more glucose. The brain and spinal cord don’t release glucose in response to glucagon; they rely on glucose coming from the blood. Muscle tissue can use its own glycogen, but it cannot export glucose to raise blood sugar, since it lacks the enzyme to release glucose into the bloodstream. Bone marrow isn’t a target for glucagon in glucose regulation.

Glucagon raises blood glucose mainly by signaling the liver. When it binds to receptors on liver cells, it raises cAMP levels, activating enzymes that break down glycogen and promote gluconeogenesis, so glucose is released into the bloodstream. Adipose tissue also responds to glucagon by activating lipolysis, releasing glycerol and fatty acids; glycerol can travel to the liver and serve as a substrate for gluconeogenesis, helping generate more glucose. The brain and spinal cord don’t release glucose in response to glucagon; they rely on glucose coming from the blood. Muscle tissue can use its own glycogen, but it cannot export glucose to raise blood sugar, since it lacks the enzyme to release glucose into the bloodstream. Bone marrow isn’t a target for glucagon in glucose regulation.