Physiology 3.2

Question 1

What is the primary role of insulin?

Answer 1

to increase glucose uptake by tissues - to lower blood glucose levels

Question 2

What are other roles of insulin?

Answer 2

Fat synthesis
Protein synthesis 
Glycogen synthesis 
Glucose oxidation
Fat, protein and glycogen breakdowns are inhibited.
Moves potassium into cells

Question 3

Which pancreatic cell secretes insulin?

Answer 3

Beta cell from islets of Langerhans.

Question 4

What is made alongside insulin, used in tests?

Answer 4

C-peptide.

Question 5

How much more does C-peptide resist degradation in comparison to insulin?

Answer 5

5x less likely to be degraded.

Question 6

What is the main stimulus causing insulin secretion?

Answer 6

Blood glucose concentration.

Question 7

What are other stimuli causing insulin secretion?

Answer 7

Amino acid concentration
Glucagon
Incretin hormones
Vagal nerve activity

Question 8

What are incretin hormones?

Answer 8

These control GI function.

Secretin, gastrin, cholecystokinin etc.

Question 9

What stimuli inhibit insulin release?

Answer 9

Low blood glucose levels.
Somatostatin (Growth hormone inhibiting hormone).
Sympathetic alpha 2 effects.
Stress ^ causing sympathetic reaction.

Question 10

How is excess glucose stored in the liver, muscles and adipose tissue?

Answer 10

Glycogen via Glycogenesis. - In muscles.

TAGs. - in adipose tissue.

Question 11

How is excess amino acids stored in adipose tissue and the liver?

Answer 11

Triacylglycerol

Question 12

How can glucose be stored?

Answer 12

As either TAGs or glycogen.

Question 13

Which tissues are insulin dependant?

Answer 13

Only adipose and skeletal muscle tissue. But this makes up 65% of the body.

Question 14

Which glucose transporter is not insulin dependant?

Answer 14

GLUT 1 (brain, kidney, red blood cells), GLUT 2(pancreas and liver), GLUT 3 (widespread)

Question 15

Which glucose transporter is insulin dependant?

Answer 15

GLUT 4 (these reside in cytoplasm not the cell surface) (adipose tissue and muscle)

Question 16

What is an insulin receptor?

Answer 16

Tyrosine kinase.

Kinase = phosphorylation = increase or decrease protein activity.

Question 17

when can muscle tissue take up glucose without insulin?

Answer 17

During exercise in an independent process.

Question 18

How does the liver take up glucose?

Answer 18

Via GLUT 2 transporters, these are not insulin dependant.

BUT insulin does enhance uptake.

Question 19

How does insulin aid in liver uptake of glucose?

Answer 19

Insulin acts on tyrosine kinase, which acts on hexokinase. Hexokinase breaks glucose into G6P - maintaining a low glucose concentration to allow more glucose to move down the concentration gradient into the liver cell through GLUT2.

Question 20

What does insulin have a permissive effect on?

Answer 20

On growth hormone

Question 21

What ion pump does insulin stimulate?

Answer 21

Sodium-potassium ATPase. It promotes K ion entry into the cell.

Question 22

How long is the half life of insulin?

Answer 22

5 minutes.

Question 23

Do you get more insulin by consuming glucose orally or IV?

Answer 23

Orally - you also get vagal stimulation and release of incretin hormones. If done IV in the blood you only get an increase in BGL.

Question 24

How does an increase in glucagon stimulate the release of insulin?

Answer 24

Because the insulin will be required to take up the new glucose created by glucagon so that BGL don’t rise too much.