Endocrine Pancreas

Question 1

What are the four types of cells in the Islets of Langerhans and what do they secrete

Answer 1

alpha cells: glucagon
beta cells: insulin
delta cells: somatostatin
F cells: pancreatic polypeptide

Question 2

What are the effects of ANS innervation of the pancreas

Answer 2

sympathetic: stimulates glucagon release and inhibits insulin release
parasympathetic: stimulates release of both insulin and glucagon n

Question 3

What are the three methods by which the cells of the islets communicate

Answer 3

gap junctions
unique nature of blood supply
innervation

Question 4

How are the islets vascularized

Answer 4

arteriole enters at the center of the islet
spread out a network of fenestrated capillaries
then converge into venules at the edge

Question 5

How is there internal innervation in the islets

Answer 5

delta cells send dendritic like processes onto beta cells to aid in coordination and communication

Question 6

How many disulfide bridges are there in insulin? how many are within the alpha chain and how many link the alpha and beta chain together

Answer 6

there are 3 disulfide bridges and one is within the alpha chain, the other two link the alpha and beta chain

Question 7

describe the synthesis of insulin

Answer 7

1.translation of mRNA yields preproinsulin
2.signal peptide is cleaved yielding proinsulin
3.proinsulin is shuttled to ER and folded with the bridges
4.proinsulin is packaged into secretory granules in Golgi
5. inside the granules, proteases cleave the c peptide yielding insulin

Question 8

If a patient is receiving exogenous insulin how could you measure their endogenous levels

Answer 8

by measuring the c-peptide in their plasma

Question 9

Briefly describe glucose mediated insulin secretion

Answer 9

1.glucose enters B cell via GLUT2 transporter
2.Glucose is phosphorylated to G6P
3.G6P is oxidized to ATP
4. ATP closes ATP sensitive K channels
5. increasing K levels depolarize beta cells
6.depolarization opens voltage gated Ca2+ channels
7.Ca2+ concentration inside cell increases
8. increased Ca2+ concentration causes exocytosis of insulin containing granules

Question 10

True/False: oral glucose is a more powerful stimulant for insulin secretion than intraveous

Answer 10

true

Question 11

What two hormones are released from enteroendocrine cells in response to oral glucose

Answer 11

GIP and GLP-1

Question 12

What are the effect of GIP and GLP-1 on insulin levels

Answer 12

stimulatory

Question 13

True/False: GI AAs, fatty acids, ketoacids directly stimulate release of insulin

Answer 13

false, they indirectly stimulate via incretins

Question 14

How does exercise inhibit insulin secretion

Answer 14

by stimulating alpha 1 andrenergic receptors on beta cells

Question 15

True/False: insulin also binds to elements in the nucleus, golgi, and ER to influence gene transcription

Answer 15

true

Question 16

Describe how insulin decreases blood glucose levels

Answer 16

-increases number of GLUT4 transporters in cell membranes
-promotes formation of glycogen in liver and muscle while inhibiting glycogenolysis
-inhibits gluconeogenesis

Question 17

Describe how insulin decreases blood fatty acid concentration

Answer 17

-stimulates storage of fatty acids in adipose
-inhibits lipolysis

Question 18

Describe how insulin decreases blood amino acid concentration

Answer 18

increases amino acid and protein uptake by tissues by activating transport systems in cell membranes

Question 19

What is insulins effect on blood K+ concentrations

Answer 19

-it promotes K+ uptake into the cells by increasing Na/K ATPase activity
-has a direct effect on the hypothalamic satiety center

Question 20

True/False: insulin has direct effect on the hypothalamic satiety center dependent on change in blood glucose levels

Answer 20

False, this action is independent of changes in blood glucose

Question 21

What organ is the primary target of glucagon

Answer 21

the liver because it stimulates hepatic glycogenolysis and gluconeogenesis