The Endocrine Pancreas

Question 1

What is the pancreas?

Answer 1

a triangular gland with both exocrine and endocrine cells located behind the stomach

Question 2

What do the acinar cells do?

Answer 2

produce enzyme rich juice for digestion

Question 3

What do the pancreatic islets do?

Answer 3

produce hormones involved in regulating fuel storage and use

Question 4

What are the cells contained within the islets and what do they produce?

Answer 4

b - cells - insulin
a- cells - glucagon
d - cells - somatostatin
F cells - pancreatic polypeptide

Question 5

What is insulin?

Answer 5

protein hormone with 2 aa chains linked by disulphide bonds

Question 6

How is insulin sythesised?

Answer 6

as proinsulin to produce 51AA insulin and Cpeptide 29aa

Question 7

On what chromosome is the DNA for insulin?

Answer 7

11

Question 8

What is the insulin synthesis pathway?

Answer 8

DNA -> mRNA -> preproinsulin (with signal peptide and c peptide) -> proinsulin -> insulin

Question 9

Why is the signal sequence required?

Answer 9

to allow the hormone into the ER

Question 10

What is insulin synthesis stimulated by?

Answer 10

glucose or feeding

Question 11

What is the threshol of glucose-stimulated insulin secretion?

Answer 11

100mg/dl

Question 12

How does glucose increase insulin secretion?

Answer 12

rapidly increases translation of mRNA and slowly increases transcription of DNA

Question 13

What is the pathway for stimulating insulin release?

Answer 13

GLUT2 brings more glucose into the cell
glucose is made into ATP
ATP closes ATP sensitive K channel
Cell depolarises and opens VGCC
Ca stimulates vesicles to exocytose by using SNARE proteins

Question 14

What are the stimulators of insulin secretion?

Answer 14

increase serum glucose, amino acids, FFA,ketone bodies

Question 15

What are the inhibitors of insulin secretion?

Answer 15

decrease glucose, amino acids, FFAs, somatostatin and epinephrine

Question 16

What are the inhibitors of insulin secretion?

Answer 16

decrease glucose, amino acids, FFAs, somatostatin and epinephrine

Question 17

What is the low threshold for insulin production?

Answer 17

50mg/dl

Question 18

When is insulin secretion half-maximal?

Answer 18

150mg/dl

Question 19

When is insulin secretion at maximal response?

Answer 19

300mg/dl

Question 20

Why is insulin secretion bi-phasic?

Answer 20

initial secretion of all insulin stores creates peak

then gradual increment as insulin is produced as long as blood glucose is high

Question 21

What is glucagon?

Answer 21

29aa polypeptide that is a hyperglycaemic agent

Question 22

What is the major target of glucagon?

Answer 22

glycogenolysis
gluconeogenesis
release of glucose to blood from liver cells

Question 23

How is glucagon synthesised?

Answer 23

DNA -> mRNA -> preproglucagon-> proglucagon -> glucagon

Question 24

What are stimulators of glucagon secretion?

Answer 24

decreased blood glucose, increased serum amino acids
stress
exercise
sympathetic nervous system

Question 25

What are inhibitors of glucagon secretion?

Answer 25

somatostatin
insulin
increased blood glucose

Question 26

What is somatostatin released in response to?

Answer 26

same things as insulin, increased blood glucose, amino acids, and fatty acids

Question 27

what does somatostatin do?

Answer 27

decreases gut motility and secretion and inhibits gastrin , CCK and GIP

Question 28

What is pancreatic polypeptide?

Answer 28

released in response to - ingestion of protein rich meal, low blood sugar, and strenuous exercise

Question 29

What does the pancreatic poly peptide do?

Answer 29

inhibits gall bladder contraction and pancreatic exocrine secretion