BSI 2 Lecture 51: Pancreas

Question 1

What 2 major tissue types make up the pancreas?

Answer 1

exocrine acini and islets of langerhans

Question 2

What 3 cell types make up the islets?

Answer 2

Alpha, beta, and gamma cells

Question 3

Which islets cell is the most numerous?

Answer 3

beta cells (60%)

Question 4

What happens in muscle cells when there is a high plasma insulin level?

Answer 4

Muscles uptake glucose and amino acids. They make glycogen and proteins

Question 5

What happens in adipocytes when there is a high plasma insulin level?

Answer 5

increased glucose uptake and utilization and triglyceride synthesis

Question 6

What happens in the liver when there is a high plasma insulin level?

Answer 6

increased glucose uptake, glycogen synthesis, and triglyceride synthesis

Question 7

What happens in muscle cells when there is a low plasma insulin level?

Answer 7

Decreased glucose uptake, glycogen catabolism, protein catabolism, amino acid release, and fatty acid uptake and utilization

Question 8

What happens in adipocytes when there is a low plasma insulin level?

Answer 8

Decreased glucose uptake, triglyceride catabolism, and release of glycerol and fatty acid

Question 9

What happens in liver cells when there is a low plasma insulin level?

Answer 9

Increased glucose release and increased ketone synthesis and release

Question 10

Does glucagon act in the opposite way of insulin?

Answer 10

It’s really just the difference in increased and decreased insulin because glucagon doesn’t have a lot of effect on muscle and adipose tissue

Question 11

Is most insulin in the blood bound or unbound, and what does that do to the half-life?

Answer 11

Most of it is unbound which gives it a shorter half-life of about 6 minutes

Question 12

Are the endocrine cells of the pancreas controlled by the hypothalamus?

Answer 12

No, they are controlled by changes in blood composition (short feedback loop)

Question 13

What mechanism does insulin use to target proteins?

Answer 13

RTK’s

Question 14

What cells does insulin bind to in order to stimulate glucose uptake?

Answer 14

Muscle cells and adipose cells

Question 15

Does insulin affect neurons?

Answer 15

No, the brain is insulin dependent

Question 16

How does increased plasma glucose cause beta cells to release insulin?

Answer 16

glucose enters the cell the GLUT-2 receptors where is it converted to ATP. This increases intracellular ATP and closes the ATP/K+ channel. Intracellular K+ levels decrease which depolarizes the cell. This causes an influx of calcium which stimulates vesicle exocytosis and secretion of insulin

Question 17

What factors stimulate the release of insulin?

Answer 17

1) glucose (primary)
2) amino acids
3) fatty acids
4) GIT hormones
5) Parasympathetic nerves
6) Amylin
7) Glucagon (A cells)
8) Sulfonylureas

Question 18

What factors inhibit the release of insulin?

Answer 18

1) Sympathetic nerves
2) B cells (negative loop)
3) D cells (Somatostatin)

Question 19

Describe the two “wave” release of insulin.

Answer 19

When the levels up blood glucose are sustained at 3x the normal rate, there is a quick surge of insulin release followed by a decreased released and then another surge of extended release. This happens because there are vesicles of insulin ready to be released, but once these are depleted, more insulin has to be made. This causes the second surge of insulin.

Question 20

What are the main counter-regulatory hormones to insulin?

Answer 20

1) glucagon
2) adrenaline
3) glucocorticoids
4) growth hormone

Question 21

Why do resting muscle cells utilize FAs for energy?

Answer 21

Because their membranes aren’t very permeable to glucose without insulin

Question 22

How does insulin promote uptake and storage of glucose?

Answer 22

It inhibits the liver phosphorylase that breaks down glycogen, increases the activity of enzymes that are involved in glycogen synthesis, and it alters glucose to a membrane-impermeable phosphate that becomes trapped

Question 23

What percentage of glucose from a meal is stored as glycogen?

Answer 23

60%