10. Pancreas

Question 1

What is the embryological origin of the pancreas?

Answer 1

Outgrowth of the foregut

Question 2

What proportion of the pancreas is responsible for exocrine secretions?

Answer 2

99%

Question 3

What is the exocrine function of the pancreas?

Answer 3

Secretion of digestive enzymes and alkaline secretions into the duodenum.

Question 4

What 2 hormones are released by the endocrine pancreas?

Answer 4

Insulin

Glucagon

Question 5

Which cells are responsible for insulin secretion?

Answer 5

Beta cells (75%)

Question 6

Which cells are responsible for glucagon secretion?

Answer 6

Alpha cells (25%)

Question 7

What name is given to the regions of the pancreas that contain endocrine cells?

Answer 7

Islets of langerhans

Question 8

What signals insulin release?

Answer 8

Feeding - glucose

Question 9

What signals glucagon release?

Answer 9

Fasting

Question 10

What are the target tissues for insulin?

Answer 10

Liver, adipose, skeletal muscle

Question 11

How do the target tissues of glucagon differ to those of insulin?

Answer 11

Glucagon doesn’t have an effect on skeletal muscle

Question 12

Which pancreatic hormone is considered anabolic?

Answer 12

Insulin

Question 13

What is the normal plasma glucose range?

Answer 13

3.3-6 mmol/L

After a meal 7-8 mmol/L

Question 14

What is the renal threshold for glucose?

Answer 14

10mmol

Question 15

What happens if glucose levels rise above the renal threshold?

Answer 15

Glucosuria

Question 16

How does the renal threshold alter in pregnant patients and elderly patients?

Answer 16

Pregnancy - decreases

Elderly - increases

Question 17

Why is it so important to tightly regulate plasma glucose levels?

Answer 17

Energy supply - brain uses glucose at a fast rate and is sensitive to depletion
Osmolarity of plasma

Question 18

What type of hormones are insulin and glucagon, how does this determine their transport in the blood?

Answer 18

Peptide hormones

Water soluble - no transport needed

Question 19

Which pancreatic hormone is anabolic?

Answer 19

Insulin

Question 20

Outline the structure of insulin.

Answer 20

2 peptide chains connected by 3 disulphide bonds

Question 21

What structural feature of insulin confers stability?

Answer 21

Disulphide bonds

Question 22

What occurs in insulin storage vesicles prior to release, how is this clinically useful?

Answer 22

Proteolysis to produce insulin + C-peptide in equal amounts. Plasma C-peptide can be used to measure levels of endogenous insulin secretion.

Question 23

How much of it’s insulin stores does the pancreas secrete each day?

Answer 23

Only 15% - rest is stored

Question 24

Which ion channel is present on the beta-cell membrane which controls insulin secretion?

Answer 24

ATP sensitive - K+ channel

Question 25

How does the ATP K+ channel regulate insulin secretion?

Answer 25

When glucose levels are high, it enters the beta cell and enters glycolysis to produce ATP. ATP binds to the K+ channel, inactivating it. Hyper polarisation of the cell opens volatage-gated calcium channels. Calcium influx triggers exocytosis of vesicles.

Question 26

What type of receptor is the insulin receptor?

Answer 26

Tyrosine kinase - alpha and beta chain

Question 27

How does insulin alter glucose uptake in target cells?

Answer 27

Inserts GLUT4 transporter to cell membranes to increase glucose uptake. Increases glycogen synthesis

Question 28

What effect does insulin have on muscle tissue?

Answer 28

Increased uptake of amino acids, increased protein synthesis.

Question 29

What effect does insulin have on adipose tissue?

Answer 29

Increases lipogenesis and TAG storage.

Question 30

How does the structure of glucagon compare to that of insulin?

Answer 30

Peptide hormone but a single chain with no disulphide bonds.

Question 31

What are the main actions of glucagon?

Answer 31

Increase glycogenolysis, gluconeogenesis, ketogenesis and lipolysis.

Question 32

What receptor type does glucagon bind to?

Answer 32

GPCR - alpha s

Question 33

The half-life of insulin in plasma is approximately?

Answer 33

5 minutes - relatively short half life to respond rapidly to changes in glucose concentration.

Question 34

How many disulphide bonds are there in insulin?

Answer 34

3 in total: 2 link the A and B chains | 1 bond within A chain

Question 35

What properties of C-peptide make it such a useful clinical marker?

Answer 35

it has a longer half life and so is more stable than insulin in plasma

Question 36

Which glucose transporter is the primary transporter of glucose in pancreatic β cells?

Answer 36

GLUT2

Question 37

Where else is GLUT2 important?

Answer 37

Liver - bi-directional so allows glucose release from gluconeogenesis as well as absorption

Question 38

What is the medical term used to describe excessive thirst?

Answer 38

Polydipsia