Physiology 3.3

Question 1

What is the main role of glucagon?

Answer 1

To raise blood glucose levels.

Question 2

Which organ does glucagon work mainly on?

Answer 2

The liver

Question 3

What are glucose-mobilizing hormones?

Answer 3

Hormones which aim to increase blood glucose levels.

Question 4

What are the 4 glucose mobilising hormones?

Answer 4

Glucagon.
Growth hormone.
Epinephrine.
Cortisol.

Question 5

Which reactions does glucagon promote?

Answer 5

Glycogenolysis (breakdown of glycogen into glucose)
Gluconeogenesis (formation of glucose from glycerol and amino acids)
Ketogenesis (production of ketones from fatty acids).

Question 6

Which pancreatic islet cell secretes glucagon?

Answer 6

Alpha cell.

Question 7

How long is the half life of glucagon?

Answer 7

5-10 mins.

Question 8

What type of hormone is glucagon?

Answer 8

A peptide hormone.

Created firstly: preprohormone - pro hormone - hormone.

Question 9

Which type of receptors does glucagon have?

Answer 9

G protein coupled receptors.

These are connected to cAMP which phosphorylates enzymes in the liver - causing them to carry out reactions.

Question 10

How is TAG broken down and what is it broken into?

Answer 10

Lipolysis = glycerol + fatty acids. these products are used in the liver to create glucose and ketones.

Question 11

Which stage of digestion is glucagon most active in?

Answer 11

The post absorptive state - when we haven’t eaten in a while it begins to work, to prevent blood glucose levels from falling too low.

Question 12

What can new glucose be created using?

Answer 12

Proteins (amino acids) would be used FIRST, followed by fat (glycerol).

Question 13

What fuel does the brain use?

Answer 13

The brain can only use glucose.

It can use ketone bodies after prolonged hypoglycaemia (in poorly controlled diabetes or starvation).

Question 14

What fuel do muscles use?

Answer 14

They primarily use fat (or protein). They can use glucose but it’s not used as often.

Question 15

How does Glycogenolysis work?

Answer 15

In the liver:

Glycogen is broken down into glucose.

Question 16

What are other glucagon stimulus?

Answer 16

Low BGL
Amino acids 
Sympathetic innervation (B2 antagonists)
stress 
cortisol - stress hormone

Question 17

How does amino acids stimulate glucagon release?

Answer 17

Because they also stimulate insulin release, therefore they need to also stimulate glucagon to ensure insulin doesn’t take up all of the glucose and cause hypoglycaemia.

Question 18

How does the sympathetic system stimulate glucagon release?

Answer 18

Because in fight or flight the body needs to increase BGL to ensure the brain (especially) and other tissues have access to enough glucose.

Question 19

What stimuli inhibit glucagon release?

Answer 19

High BGL
Free fatty acids and ketones
Insulin
Somatostatin

Question 20

Which reactions does glucagon decrease?

Answer 20

Lipogenesis

Question 21

How does free fatty acids inhibit glucagon release?

Answer 21

Because glucagon decreases lipogenesis. Therefore taking glucagon away will increase lipogenesis, increasing the fatty acid production into TAGs and removing the fatty acids from the blood.

Question 22

What does parasympathetic activity do to insulin and glucagon?

Answer 22

Increases insulin
Increases glucagon (a little bit) 

We sense food and the vagus nerve prepares the body for a rise in glucose by recreating insulin. However we also need to secrete glucagon to prevent hypoglycaemia.

Question 23

What does sympathetic activity do to insulin and glucagon?

Answer 23

Decreases insulin
increases glucagon (a lot)
Increases epinephrine

The body needs HBG to supply the brain especially with glucose. Even though the muscles and adipose tissue are insulin dependant, they don’t need to absorb as much glucose because they mainly use fat (or protein).

Question 24

Why are there 4 glucose mobilising hormones?

Answer 24

To prove how important it is for blood glucose levels not to fall too low (or you will die).

Question 25

What effect does growth hormone and cortisol have on insulin?

Answer 25

It is antagonistic (inhibits glucose uptake).

Question 26

what hormone breaks down proteins?

Answer 26

Cortisol

Question 27

What does Cushings syndrome do?

Answer 27

Increases cortisol levels - antagonistic against insulin. This raises blood glucose levels giving diabetic symptoms. (same with too much growth hormone).

Question 28

What is the other name for somatostatin?

Answer 28

GHIH.

Growth hormone inhibiting hormone.

Question 29

Which pancreatic cells release somatostatin?

Answer 29

Delta cells.

Question 30

What other endocrine organ secretes somatostatin?

Answer 30

The hypothalamus.

Question 31

What is the pancreatic action of somatostatin?

Answer 31

To decrease GI function (often given in severe diarrhoea).

Prevents mass flux in absorption and plasma concentration peaks.

Question 32

What effects does somatostatin have on insulin and glucagon?

Answer 32

Inhibits alpha and beta cells so inhibits their release.

Does this paracrine - a local reaction to the other islet cells.

Question 33

what symptoms do you get in a somatostatin producing tumour?

Answer 33

Diabetic symptoms that go away once the tumour is removed.