Endocrine Pancreas

Question 1

Define the pancreas?

Answer 1

Triangular gland

Which has both exocrine and endocrine cells

Located behind the stomach.

Question 2

Exocrine?

Answer 2

Secretes into a duct

Question 3

Endocrine?

Answer 3

Secretes directly into the blood stream

Question 4

What are the cells in the pancrease that produce exocrine product?

Answer 4

Acinar cells.

Produce an enzyme-rich juice used for digestion

Question 5

What is the name for the cells that produce endocrine products?

Answer 5

Pancreatic islets.

Islets of langerhans.

Produce hormones involved in regulating fuel storage and use.

Question 6

What are the key parts of the pancreas?

Answer 6

Pancreatic duct (goes into the lumen of the gut)

Islets

Pancreatic acinar cells

Question 7

the different cells in the Islets of Langerhans?

Answer 7

Beta cells: produce insulin

alpha cells: produce glucagon

Delta cells: produce somatostatin.

F cells: produce pancreatic polypeptide.

Question 8

The location in the pancreas of the cell types?

Answer 8

Question 9

Insulin?

Answer 9

Protein hormone

Consisting of two amino acid changes linked by disulfide bonds.

Produced as pro-hormones first until they reach the site of action.

Question 10

Why are enzymes synthesised as pro-enzyme instead of active enzyme?

Answer 10

So the do not digest the cells they are manufactored in.

eg. if insulin were to be active it would digest the pancreatic cells.

Question 11

Insulin synthesis?

Answer 11

DNA (in beta cells) ->

mRNA ->

Preproinsulin (contains an addition polypeptide sequence at the N-terminal) —>

Proinsulin —>

Insulin

Question 12

Insulin synthesis and release?

Answer 12

mRNA binds to preprohormone.

Enzymes in the ER remove the signal sequence producing prohormone.

Prohormone passes from ER to Golgi apparatus.

Secretory vesicles contain enzymes and prohormones making hormone.

Hormone is released into the extracellular space

Question 13

What effects the synthesis of insulin?

Answer 13

Glucose or feeding

Decreased by fasting

Question 14

What is the threshold of glucose-stimulated insulin secretion?

Answer 14

100mg/dl

Question 15

How does glucose stimulate insulin secretion?

Answer 15

GLUT2 uptakes glucose into the beta cells.

Glycolysis- increase in ATP.

ATP-sensitive potassium channel- inward movement of potassium.

Depolarisation of the cell.

Inward calcium movement: by voltage-gated calcium channel.

This calcium stimulates the release of the insulin vesicles.

Question 16

Regulators of insulin secretion?

Answer 16

Stimulators:

Increase in serum glucose.

Hormones.

Inhibitors:

Decrease glucose

Hormone: SS.

Question 17

What level of plasma glucose when no insulin is produced?

Answer 17

below 50mg/dl

Question 18

What level of plasma glucose when half-maximal insulin response occurs?

Answer 18

At 150mg/dl

Question 19

What level of plasma glucose conc when a maximum insulin response occurs?

Answer 19

At 300mg/dl

Question 20

Insulin is biphasic?

Meaning

Answer 20

It has two phrases of production

upon glucose stimultion: initial burst.

second phase: gradual increment. Lasts as long as blood glucose levels are high

Question 21

Graph representing the insulin secretion?

Answer 21

Peak straight after increase in glucose levels.

Question 22

Glucagon?

Answer 22

Polypeptide hormone

Potent hyperglycemic agent.

Produced by alpha cells in the pancreas

Question 23

What does glycagon target and what does it promote?

Answer 23

Major target is the liver.

Promotes glycogenolysis: breakdown of glycogen to glucose.

Gluconeogenesis: synthesis of glucose from lactic acid.

Release of glucose to the blood from liver cells.

Question 24

Glucagon synthesis?

Answer 24

DNA in alpha cells

mRNA

Preproglycagon

Proglycagon

Glycagon

Question 25

Factors affecting glucagon secretion?

Answer 25

Stimulation:

decrease in blood glucose, Increase in serum amino acid, stress and exercise.

Inhibitiors:

SS, Insulin, increase in blood glucose

Question 26

What kind of feedback happens on glucagon when the plasma glucose increase?

Answer 26

Negative feedback onto the alpha cells

Decreases the glycagon levels

Question 27

Insulin and Glucagon together?

Answer 27

Regulate metabolism

A balancing act.

Levels of glucose in blood low: glucagon needed.

Level of glucose are high: insulin needed.

Question 28

Somatostatin?

Answer 28

Secreted by delta cells.

Inhibitory effects.

Released to same stimuli as insulin.

Question 29

Pancreatic polypeptide hormone?

Answer 29

Secreted by the F cells

Release in response to the high protein meal, low blood sugar and stenous exercise.

Inhibits gall bladder and pancreatic exocrine secretion.