Session 10-Endocrine Pancreas

Question 1

What are the two functions of the pancreas?

Answer 1

• produces digestive enzymes secreted directly into duodenum (exocrine)
• hormone production (endocrine)

Question 2

True or false: exocrine functions form the bulk of the pancreas gland

Answer 2

TRUE

Question 3

Where is the endocrine function of the pancreas carried out?

Answer 3

Islets of Langerhans

Question 4

Which polypeptide hormones are secreted by the pancreas? (7)

Answer 4

Insulin
Glucagon
Somatostatin
Pancreatic polypeptide (PP)
Ghrelin
Gastrin 
Vasoactive intestinal peptide

Question 5

Which cells in the islets produce each of the important polypeptide hormones?

Answer 5

Insulin-beta cells
Glucagon-alpha cells
Somatostatin-delta cells
Pancreatic polypeptide-PP
Ghrelin-e cells
Gastrin-G cells

Question 6

How does insulin affect blood glucose levels?

Answer 6

Lowers

Question 7

How does glucagon affect blood glucose levels?

Answer 7

Raises

Question 8

Which tissues does insulin target?

Answer 8

Liver
Adipose
Skeletal muscle

Question 9

Which tissues can glucagon target?

Answer 9

Liver

Adipose

Question 10

True or false: insulin has catabolic activity

Answer 10

FALSE - anabolic

Question 11

What is the normal range of plasma glucose?

Answer 11

3.3-6 mmol/L

Question 12

When does glycosuria occur?

Answer 12

If plasma glucose > 10 mmol/L

Question 13

What are the properties of insulin and glucagon?

Answer 13

Water soluble hormones:

• carried dissolved in plasma
• short half life
• interact with cell surface receptors on target cells
• receptor with hormone bound can be internalised

Question 14

Describe the structure of insulin

Answer 14

Big peptide with alpha helix structure, consists of two unbranched peptide chains which are connected by 2 disulphide bridges - ensures stability

Question 15

What is the precursor for insulin?

Answer 15

Preproinsulin

Question 16

What does C peptide do?

Answer 16

Helps prevent vascular damage in diabetic patients

Question 17

What do K-ATP channels do?

Answer 17

• ATP sensitive potassium channel on cell membrane

- Allows K+ efflux out of cell-drags membrane potential down and hyperpolarises cell membrane

Question 18

What inhibits K ATP channels?

Answer 18

ATP

Question 19

Describe how K ATP channels are regulated by metabolism?

Answer 19

Glucose closes K ATP channels in pancreatic beta-cells - no K+ leaving so membrane depolarises because glucose is on the outside of the beta cell and glucose will enter and ATP production will inhibit ATP sensitive K+ channels

Question 20

How are K ATP channels and insulin secretion related?

Answer 20

Membrane depolarises -> voltage gated Ca2+ channels open and intracellular Ca2+ increases and vesicles with insulin fuse to side of beta cell and insulin released

Question 21

What are the metabolic effects of insulin?

Answer 21

-increases glucose uptake into target cells and glycogen synthesis by insertion of GLUT4 channel

Question 22

What effect does insulin have in the liver?

Answer 22

Increases glycogen synthesis by stimulating glycogen formation and inhibiting breakdown

Question 23

What effect does insulin have in muscles?

Answer 23

Increases uptake of AA promoting protein synthesis

Question 24

What effect does insulin have in adipose tissue?

Answer 24

Increases storage of triglycerides

Question 25

Which cells secrete glucagon?

Answer 25

Pancreatic alpha cells

Question 26

Why does glucagon not have disulphide bridges?

Answer 26

Allows for flexibility

Question 27

What are the effects of glucagon?

Answer 27

- stimulates glycogenolysis in liver - stimulates gluconeogenesis - net effect is rise in blood glucose levels - stimulates lipolysis to increase plasma fatty acid

Question 28

Why does an increase in amino acids lead to an increase in glucagon?

Answer 28

Starvation mode - body starts to digest own musculature where high AA tries to stimulate glucagon to release glucose

Question 29

Describe the speed of the following processes: 1) glucose uptake in muscle and adipose tissue 2) gluconeogenesis 3) glycogenesis 4) lipogenesis 5) lipolysis 6) amino acid uptake 7) protein synthesis

Answer 29

1) rapid (seconds) 2) intermediate (minutes) 3) intermediate (minutes) 4) delay (hours) 5) rapid (seconds) 6) rapid (seconds) 7) intermediate (minutes)

Question 30

What does a high level of insulin lead to?

Answer 30

Hypoglycaemia

Question 31

What does a low level of insulin lead to?

Answer 31

Hyperglycaemia - diabetes mellitus

Question 32

What does a high level of glucagon lead to?

Answer 32

Makes diabetes worse

Question 33

What does a low level of glucagon lead to?

Answer 33

May contribute to hypoglycaemia

Question 34

What causes type 1 diabetes?

Answer 34

Absolute insulin deficiency - autoimmune destruction of pancreatic beta cells

Question 35

What is absolute type 1 diabetes?

Answer 35

Pancreatic beta cells destroyed

Question 36

What is relative type 1 diabetes?

Answer 36

Secretory response of beta cell is abnormally slow or small

Question 37

What causes type 2 diabetes?

Answer 37

- Defective insulin receptor mechanism - change in receptor number and/or affinity - Defective post-receptor events - excessive or inappropriate glucagon secretion

Question 38

Describe the process of insulin resistance in the young

Answer 38

1) Initially, beta cells compensate by increasing insulin production-maintains normal blood glucose 2) eventually, beta cells unable to maintain increased insulin production-impaired glucose tolerance 3) finally, beta cell dysfunction leads to relative insulin deficiency-overt type 2 diabetes