Pancreas

Question 1

What are the major cells in the Islets of Langerhans?

Answer 1

Alpha
Beta
Delta
PP
Epsilon

Question 2

What is the function of alpha cells?

Answer 2

Make glucagon

Question 3

What is the function of beta cells?

Answer 3

Make insulin

Question 4

What is the function of delta cells?

Answer 4

Make somatostatin (SS14)

Question 5

What is the function of PP cells?

Answer 5

Secrete pancreatic polypeptide

Question 6

What is the function of epsilon cells?

Answer 6

Make ghrelin

Question 7

What is the major function of insulin?

Answer 7

Energy storage (anabolic hormone)

Question 8

What is the major function of glucagon?

Answer 8

Energy mobilization (catabolic hormone)

Question 9

Describe the arrangement of alpha and beta cells.

Answer 9

Beta cells clustered in “core”; other cells in “mantle.”

Alpha cells surround beta cells in a sandwich formation and the line the outer capillaries.

Question 10

How does blood flow in the Islets of Langerhans?

Answer 10

Blood feeds the center of the Islet and then

flows outward

Question 11

Describe the processing of insulin.

Answer 11

Insulin is released with C-peptide and the C chain is cleaved off which is necessary for insulin to bind to its receptor

Question 12

What is the function of C-peptide?

Answer 12

C peptide has a long half life in the blood and is used to measure pancreatic function

Question 13

How does glucose outside of the beta cell stimulate the initiation of insulin release?

Answer 13

Transported into cell by GLUT-2, which has LOW affinity for glucose. Only when glucose is high will it transport.

Question 14

What happens to glucose once it is transported into the beta cell?

Answer 14

Glucose will be turned into G6P only when the glucose levels are high as glucokinase has a low affinity for glucose.

G6P will be metabolized and it will generate ATP.

Question 15

What happens with increased ATP levels in the beta cell?

Answer 15

Increased ATP will cause the cell’s K+ channels to close and as a result, K+ will accumulate within the cell.

Question 16

What is the function of sulfonylurea drugs?

Answer 16

They will also close the K+ channels in the beta cell, bypassing the glucose steps

Question 17

What happens with increased K+ within the beta cell?

Answer 17

It will cause the cell to depolarize and Ca2+ channels to open.

Question 18

What happens to the beta cell with the opening of the Ca2+ channels?

Answer 18

The Ca2+ influx will will cause the exocytosis of insulin vesicles

Question 19

How do FFAs and AAs affect insulin release?

Answer 19

They will increase it as both can generate ATP within the beta cell as well

Question 20

What is the biphasic insulin response following a meal?

Answer 20

1 - there is an initial insulin spike signaling the release of insulin that has already been docked at the membrane

2 - the rising slope after the drop signals newly synthesized insulin being released

Question 21

What is the insulin receptor and how does it work?

Answer 21

It is a tyrosine kinase receptor and insulin binds receptor at alpha subunit and the beta subunit is autophosphorylated

Question 22

What is the action of insulin in the muscle cell?

Answer 22

It allows for muscles to uptake glucose via GLUT4, otherwise, muscles cannot intake glucose.

Question 23

What is the pathway for insulin action of the muscle cell?

Answer 23

• Autophosphorylation of receptor recruits IRSs (insulin receptor substrates).
• IRSs activate intracellular signaling cascades

RESULT: GLUT-4 inserted in membrane – glucose can enter cell

Question 24

Which of the glucose transporters is glucose independent?

Answer 24

GLUT-1, 2, 3 are all insulin independent

Question 25

What glucose transporter is glucose dependent?

Answer 25

GLUT-4 in muscle

Question 26

What is the effect of insulin on the liver?

Answer 26

Promotes glycogen and TAG production Reduces glucose production/output

Question 27

What is the effect of insulin on muscle?

Answer 27

Promotes glycogen and TG production and protein synthesis

Question 28

What is the effect of insulin on fat?

Answer 28

Promotes TAG production, release of FFAs from chylomicrons, glycolysis

Question 29

How is glucagon processed in the pancreatic alpha cell?

Answer 29

GRPP is cleaved from GLUC and is inactive GLP-1 and 2 (Incretins) are not cleaved an inactive GLUC is cleaved free and is active

Question 30

How is glucagon processed in the intestinal L cell?

Answer 30

GRPP-GLUC is not cleaved and remains inactive as glicentin The incretins GLP-1 and 2 are cleaved in the intestine and active.

Question 31

What is the function of incretins?

Answer 31

They increase the amount of insulin released from the pancreas

Question 32

When is glucagon released?

Answer 32

Major counterregulatory hormone to insulin – most things that stimulate insulin will inhibit glucagon. Released in response to low blood glucose levels.

Question 33

What effect do AAs have on glucagon release?

Answer 33

AAs stimulate release (protein meals)

Question 34

What effect do catecholamines have on glucagon release?

Answer 34

Catecholamines stimulate release (exercise)

Question 35

What is the effect of insulin on ketogenesis?

Answer 35

Insulin will inhibit ketogenesis

Question 36

What is the function of somatostatin (SS14)?

Answer 36

Suppresses insulin release - used in clinic for management of insulin-producing tumors

Question 37

What is the regulation of SS14?

Answer 37

Produced by delta cells in pancreatic islets Stimulated by high fat, high carb meals. Inhibited by insulin

Question 38

What is the function of amylin?

Answer 38

Released with insulin from vesicles in beta cells | Synergistic with insulin in regulation of blood glucose

Question 39

What is the function of ghrelin?

Answer 39

Stimulates food intake at level of hypothalamus Stimulates GH release Inverse correlation between circulating ghrelin and obesity

Question 40

What are the main counter regulatory hormones to insulin?

Answer 40

Glucagon Growth Hormone Cortisol Catecholamines