Physio: Endocrine - Endocrine Pancreas

Front 1

What hormone is secreted by the alpha cells of the islets of Langerhans?

Back 1

glucagon

Front 2

In what part of the islet are the alpha cells located?

Back 2

outer rim

Front 3

What hormone is secreted by the beta cells of the islets of Langerhans?

Back 3

insulin

Front 4

In what part of the islet are the beta cells located?

Back 4

center

Front 5

What hormone is secreted by the delta cells of the islets of Langerhans?

Back 5

somatostatin (and gastin)

Front 6

In what part of the islet are the delta cells located?

Back 6

intermixed

Front 7

What are 3 ways in which the cells communicate with each other?

Back 7

1) gap jns (a-a, b-b, and a-b)
2) portal blood supply (venous blood from one cell type bathes other cell types)
3) via nervous innervation

Front 8

What is the structure of proinsulin?

Back 8

A chain and B chain connected by C peptide

Front 9

What is the significance of the C peptide?

Back 9

it's conc is used to monitor beta cell fn in diabetic pts receiving exogenous insulin (b/c it's secreted along w/insulin)

Front 10

Describe the cellular mechanism of insulin secretion.

Back 10

1. Gluc binds GLUT 2 on beta cell, moves into cell
2. Gluc is oxidized to ATP
3. ATP binds and closes K channel, cell depolarizes
4. Ca channels open, Ca rushes in
5. Stimulates insulin release

Front 11

Which is a more powerful stimulant for insulin secretion: oral glucose or intravenous glucose? Why?

Back 11

oral; it stimulates s/c of gastric inhibitory peptide (GIP), which has independent stimulatory effect on insulin

Front 12

What class of drugs mimics the action of ATP in beta cells (closing K channels to depolarize the cell)?

Back 12

sulfonylurea drugs (e.g. tolbutamide, glyburide)

Front 13

For what condition are sulfonylurea drugs most commonly administered?

Back 13

type II (non-insulin dependent) diabetes mellitus

Front 14

What is the structure of the insulin receptor?

Back 14

2 extracellular alpha subunits which connect 2 membrane spanning beta subunits with tyrosine kinase activity (autophosphorylation)

Front 15

Under what conditions does insulin up-regulate and down-regulate its own receptor? How?

Back 15

up-regulates during starvation, down-regulates during obesity (type II diabetes); it internalizes receptor after binding, and can inc or dec degradation/recycling

Front 16

What are the mechanisms by which insulin decreases blood glucose concentration?

Back 16

1. directs insertion of glucose transporters in cell membranes
2. promotes formation of glycogen in musc & liver, and inhibits glycogenolysis
3. inhibits gluconeogenesis

Front 17

By what biochemical mechanism does insulin inhibit gluconeogenesis?

Back 17

stimulates fructose 2,6-biphosphatase, which increases phosphofructokinase activity

Front 18

What are the mechanisms by which insulin decreases blood fatty acid and ketoacid concentration?

Back 18

stimulates fat deposition and inhibits lipolysis, which decreases amount of available acetyl CoA, which inhibits ketoacid formation

Front 19

What are the mechanisms by which insulin decreases blood amino acid concentration?

Back 19

stimulates AA uptake, increases protein synthesis, inhibits protein degradation

Front 20

What are the menchanisms by which insulin decreases blood K concentration?

Back 20

increases K uptake into cells by increasing activity of Na-K ATPase

Front 21

What is the overall effect on insulin on blood levels of glucose, amino acids, fatty acids, ketoacids, and potassium?

Back 21

decreased gluc, aa, fatty acids, ketoacids, and K

Front 22

What are some factors that stimulate insulin secretion?

Back 22

inc blood glucose, aa's, and fatty acid, glucagon, GIP, ACh, growth hormone, and cortisol (neg feedback?)

Front 23

What are some factors that inhibit insulin secretion?

Back 23

dec blood glucose, somatostatin, epinephrine, NE

Front 24

What symptoms would a patient with type I (insulin-dependent) diabetes mellitus present with?

Back 24

hyperglycemia, hyperkalemia, hypotension (gluc acts as osmotic diuretic), ketone breath, metabolic acidosis (from ketoacids), hyperventilation (respiratory compensation)

Front 25

What factors stimulate glucagon secretion?

Back 25

dec blood glucose, INCREASED AAs (esp arginine), CCK, NE, epin, ACh

Front 26

What factors decrease glucagon secretion?

Back 26

inc blood glucose, insulin, somatostatin, fatty acids, ketoacidds

Front 27

What are the major actions of glucagon?

Back 27

stimulates glycogenolysis and gluconeogenesis, inhibits glycogen formation, increases lipolysis and ketoacid formation

Front 28

What is the 2nd messanger mechanism of action for glucagon?

Back 28

cAMP

Front 29

What is the effect of somatostatin?

Back 29

inhibit secretion of both insulin and glucagon (modulatory effect)

Front 30

What stimulates secretion of somatostatin?

Back 30

ALL forms of nutrients, various GI hormones, glucagon, beta-adrenergic agonists (is inhibited by insulin)