lecture 2 - insulin & glucagon

Question 1

How does glucose trigger insulin secretion?

Answer 1

1. Glucose enters pancreatic Beta cells via GLUT2 transporters
2. GLucose is converted to Glucose-6-phosphate by glucokinase.
3. G-6-P is oxidised to ATP, which triggers K+ channels to open and depolarise the cells.
4. This triggers voltage gated calcium channels to open, promoting exocytosis of insulin

Question 2

What is the key characteristic of GLUT2 receptors?

Answer 2

They are insulin independent - they respond to glucose levels rather than insulin levels

Question 3

What is the key characteristic of GLUT-4 receptors?

Answer 3

They are insulin dependent glucose transporters. They rely on insulin for transport to the cell surface so that glucose can be taken up by the cell.

Question 4

Where does reabsorption of glucose occur in the nephron?

Answer 4

Proximal tubule

Question 5

Which hormones potentiate insulin secretion from Beta cells?

Answer 5

cholecystokinin, incretins

Question 6

Which hormones inhibit insulin secretion from Beta cells?

Answer 6

Adrenaline, glucagon

Question 7

What are incretins?

Answer 7

Gut hormones that help to control blood glucose levels by stimulating insulin release, altering gut absorbance, and affecting appetite.

Question 8

What are some key examples of incretins?

Answer 8

GLP-1, GIP

Question 9

What are the promotor affects of insulin?

Answer 9

promotes glucose uptake in muscle/adipose, promotes glycogen synthesis in liver/muscle, promotes lipogenesis in adipose/liver, promotes glucose utilisation (glycolysis), promotes protein synthesis, promotes lipoprotein lipase activity to promote fatty acid uptake in adipose

Question 10

What are the inhibitory effects of insulin?

Answer 10

Inhibits gluconeogenesis and glycogenolysis in the liver, inhibits hormone sensitive lipase

Question 11

What are the effects of insulin on the liver?

Answer 11

Increased glycogen synthesis and lipogenesis, reduced gluconeogenesis

Question 12

What are the effects of insulin on muscle?

Answer 12

Increased glucose uptake and glycogen synthesis

Question 13

What are the effects of insulin on the pancreas?

Answer 13

Decreased alpha cell secretion

Question 14

What are the effects of insulin on adipose tissue?

Answer 14

Increased glucose uptake, lipoprotein lipase activy and TAG storage.
Decreased lipolysis

Question 15

What is adiponectin?

Answer 15

A peptide hormone produced in adipose tissue that assists insulin in glucose regulation

Question 16

Where are glucagon receptors found?

Answer 16

liver cells, adipocytes

Question 17

What are the 3 key stimuli for a glucagon secretion?

Answer 17

low blood glucose, anoxia, adrenaline

Question 18

What are the effects of glucagon on the liver?

Answer 18

Promotes glycogenolysis and gluconeogenesis and the release of glucose

Question 19

What are the effects of glucagon on adipose?

Answer 19

Promotes lipolysis and the release of fatty acids

Question 20

Where are adrenaline receptors located in the body?

Answer 20

Liver, muscle, adipocytes

Question 21

What are the metabolic effects of adrenaline?

Answer 21

Acts like glucagon to release glucose and fatty acids - promotes glycogenolysis, gluconeogenesis, lipolysis, glucagon release.

Question 22

Why is trauma often associated with hyperglycaemia?

Answer 22

Often causes a release of adrenaline, which triggers the mobilisation of stored fuels

Question 23

What are glycogen storage diseases?

Answer 23

Diseases caused by enzyme dysfunction/deficiency in the liver or muscle that prevents adequate storage of glucose as glycogen