Exam 3- The Endocrine Pancreas

Question 1

what nerves innervate the pancreas?

Answer 1

sympathetic and parasympathetic nerves
synapse directly on pancreatic cells

Question 2

what does the sympathetic nervous system stimulate in the pancreas?

Answer 2

glucagon release
inhibits insulin release

Question 3

what are the functional units of the endocrine pancreas?

Answer 3

islets of langerhans

Question 4

what mass of the pancreas does the endocrine pancreas make up and how much of the overall pancreatic blood flow does it receive?

Answer 4

2%
10%

Question 5

what are the cell types in the islets of langerhans?

Answer 5

alpha cells
beta cells
delta cells
F cells

Question 6

what do alpha cells secrete?

Answer 6

glucagon

Question 7

what do delta cells secrete?

Answer 7

somatostatin

Question 8

how do cells communicate in the islets of langerhans?

Answer 8

gap junctions
blood supply
innervation

Question 9

what is unique about the blood supply of the islets of langerhans?

Answer 9

arteriole enters center, spreads out it network fenestrated capillaries, then converges into venules
carries insulin from beta cells to alpha and delta cells

Question 10

what cells perform regulatory functions from inside the islets of langerhans?

Answer 10

delta cells send dendrite-like processes onto beta cells

Question 11

what is the overall structure of insulin?

Answer 11

peptide hormone: A and B chains with connecting peptide
2 disulfide bonds between A and B chains, one more within A chain

Question 12

what electrolyte is important for releasing insulin from the secretory granules?

Answer 12

calcium

Question 13

what is released with insulin from the granules?

Answer 13

C-peptide in equal proportion

Question 14

true/false: insulin activity is highly species specific

Answer 14

false

Question 15

what is the first step of insulin synthesis?

Answer 15

translation of mRNA

Question 16

what transporter is on beta cells that allows glucose into the cells?

Answer 16

GLUT2: facilitated diffusion

Question 17

what happens to glucose inside of the pancreatic beta cell?

Answer 17

phosporylated to glucose-6-phosphate by glucokinase

Question 18

what happens to glucose-6-phosphate inside the beta cell?

Answer 18

oxidized, producing ATP

Question 19

why is the production of ATP important for secreting insulin?

Answer 19

it closes ATP-sensitive K+ channels, decreasing conductance and leading to beta cell becoming depolarized

Question 20

what does depolarization of the beta cell lead to?

Answer 20

opening of voltage-gated Ca++ channels and increasing Ca++ concentration inside the cell

Question 21

what does increased Ca++ concentration inside the beta cell lead to?

Answer 21

Ca++ mediated exocytosis of insulin-containing granules

Question 22

is oral or intravenous glucose a stronger stimulator of insulin secretion?

Answer 22

oral glucose

Question 23

what hormones does oral glucose stimulate?

Answer 23

glucose dependent insulinotropic peptide (GIP) and glucagon-like peptide 1 (GLP-1)

Question 24

what is the structure of the insulin receptor?

Answer 24

tetramer with 2 alpha and 2 beta subunits

Question 25

what is the mechanism of action of the insulin receptor?

Answer 25

insulin binds to alpha subunits conformational change in beta subunits: activated tyrosine kinase activity phosphorylates other proteins and enzymes insulin-receptor complex internalized and degraded or recycled

Question 26

does insulin bind to other places than the insulin receptor?

Answer 26

yes- in nucleus, golgi, and endoplasmic reticulum to influence gene transcription

Question 27

how does insulin decrease blood glucose?

Answer 27

increases GLUT4 transporters in cell membranes promotes formation glycogen from glucose in muscle and liver inhibits glycogenolysis inhibits gluconeogenesis

Question 28

what does insulin do to blood fatty acid concentration?

Answer 28

lowers it: stimulates storage and inhibits lipolysis

Question 29

how does insulin affect blood amino acid concentration?

Answer 29

increased amino acid and protein uptake by tissues

Question 30

does insulin affect the hypothalamic satiety center?

Answer 30

yes- direct effect

Question 31

what is glucagon's primary target?

Answer 31

liver

Question 32

what cells release glucagon?

Answer 32

alpha cells

Question 33

what is the direction of blood flow in the pancreas?

Answer 33

center to periphery dense network fenestrated capillaries

Question 34

what percentage of the islet of langerhans do beta cells make up?

Answer 34

65%

Question 35

what do F cells secrete in the endocrine pancreas?

Answer 35

pancreatic polypeptide

Question 36

what nerves carry the sympathetic and parasympathetic innervation to the endocrine pancreas?

Answer 36

splanchnic nerves carry sympathetic (celiac ganglion) vagus nerve carries parasympathetic

Question 37

between what cells are gap junctions in the endocrine pancreas?

Answer 37

beta cells and beta cells alpha cells and beta cells

Question 38

what is the sequence of events for insulin synthesis?

Answer 38

translation of mRNA: preproinsulin signal peptide cleaved: proinsulin shuttled to endoplasmic reticulum secretory granules in golgi proteases cleave connected peptide

Question 39

what does exercise do to insulin secretion?

Answer 39

inhibits it: stimulates alpha-1 adrenergic receptors on beta cells: prevents hypoglycemia