Exam 2 (Lecture 12) - Endocrine Pancreas, Insulin, and Glucagon

Question 1

Which gland secretes insulin and glucagon, what is the chemical nature of these hormones and what are the main aspects of their action?

Answer 1

1) The pancreatic islets (Islets of Langerhans)

2) Peptide hormones

3) Functions:
- rapid and powerful regulators of metabolism
- coordinate deposition of nutrients inputs from meals, flow of endogenous substrate during fasting, both effects achieved via actions on liver, adipose tissue, and muscle mass

** Often secreted reciprocally

Question 2

Name four hormones that oppose the anabolic function of insulin (insulin is anabolic - it increases storage of glucose, fatty acids, and amino acids).

Answer 2

1) Growth hormone

2) Epinephrine and norepinephrine (catecholamines)

3) Cortisol

4) Glucagon

Question 3

Which anatomical arrangement predisposes the liver to be the primary target of insulin and glucagon?

Answer 3

The portal vein system which is a conglomeration of the mesenteric vein and the pancreatic vein bringing the nutrients, insulin, and glucagon together to do their jobs.

Question 4

What are the effects of insulin on fuel storage and breakdown in the insulin sensitive tissues (liver, muscles, and adipose)?

Answer 4

Insulin inhibits fuel breakdown and stimulates fuel storage.

Question 5

How does insulin facilitate glucose uptake in muscle and adipose tissue? How does it facilitate glucose uptake in the liver?

Answer 5

1) GLUT4 (regulated by insulin) facilitates glucose diffusion into cells of adipose tissue and muscle
- insulin stimulates cells in the adipose tissue and muscle to incorporate more GLUTs into their membranes

2) GLUT2 mediates glucose diffusion to and from hepatocytes
- insulin stimulates phosphorylation of intracellular glucose to maintain a high concentration gradient

Question 6

Which stimuli are the main triggers of glucagon secretion?

Answer 6

Lowering of plasma glucose and increase of plasma amino acids.

Question 7

What are the main effects of glucagon on flow of fuels and how do these effects differ from effects of insulin?

Answer 7

1) Causes lypolysis in adipose tissue, hepatic gluconeogenesis, and glycogenolysis.

2) They are opposite effects of insulin.