Lecture 4 The Endocrine Pancreas 1&2

Question 1

Define Glucostatic Theory

Answer 1

Food intake is determined by blood glucose. As BG increases the drive the eat decreases

Question 2

Define Lipostatic Theory

Answer 2

Food intake is determined by fat stores, as fat stores increase the drive to eat decreases. Leptin is a peptide hormone released by fat stores to depress feeding activity

Question 3

Which energy output can the human body egulate

Answer 3

Mechanical work as it is voluntary

Question 4

What is the absorptive state

Answer 4

Where ingested nutrients supply the energy needs of the body and the excess is stored (anabolic phase)

Question 5

What is the Post-absorptive phase

Answer 5

Fasted State where we rely on body stores to provide energy (catabolic phase)

Question 6

Why is the brain referred to as an obligatory glucose utiliser

Answer 6

Brain can only use glucose except in extra cases of starvation in which it uses ketones

Question 7

What is the normal BG range

Answer 7

4.2-6.3mM (80-120mg/dl)

5mM

Question 8

When is someone BG hypoglycaemic

Answer 8

<3mM

Question 9

What are the 4 types of islet cells in the Islets of Langerhans

Answer 9

alpha cells produce GLUCAGON
beta cells produce INSULIN
delta cells produce SOMATOSTATIN
F cells produce pancreatic polypeptide

Question 10

Describe how insulin goes from its active form to inactive

Answer 10

Preproinsulin
Proinsulin in ER
Proinsulin in cleaved in Golgi
Insulin and C-peptide

Question 11

Excess glucose is stored as

Answer 11

Glycogen in liver

Triacylgycerides in liver and adipose tissue

Question 12

Excess amino acids is stored as

Answer 12

Fat and form an energy source

Question 13

Fatty acids are stored as

Answer 13

Triglycerides

Question 14

Describe the mechanism of insulin secretion when glucose is abundant

Answer 14

Glucose enters cells through GLUT and metabolism increases
This increases [ATP] within the cell causing the KATP channel to close
Intracellular [K+ ] rises, depolarising the cell. Voltage-dependent Ca2+ channels open and trigger insulin vesicle exocytosis into the circulation.

Question 15

Describe the mechanism of insulin secretion when glucose is low

Answer 15

ATP is low low so KATP channels are open so K+ ions flow out removing +ve charge from the cell and hyperpolarizing it, so that voltage-gated Ca2+ channels remain closed and insulin is not secreted.

Question 16

Describe the primary action of Insulin

Answer 16

1. Binds to tyrosine kinase receptors on the cell membrane of insulin-sensitive tissues to increase glucose uptake by these tissues
2. Phosphorylates IRS
3. Second messeger alter protein synthesis
4. membrane transport modified
5. Cell metabolism is changed

Question 17

Where is GLUT 2 located

Answer 17

plasma membrane of the liver, pancreatic, intestinal, kidney cells

Question 18

Where is GLUT 4 located

Answer 18

cytoplasm of muscle and adipose tissue cells. When stimulated by insulin GLUT4 migrates to the membrane and is then able to transport glucose into the cell. When insulin stimulation stops, the GLUT-4 transporters return to the cytoplasmic pool

Question 19

What tissues are insulin dependent

Answer 19

Muscle and Adipose tissue

Question 20

What tissue isn’t insulin dependent

Answer 20

Liver

Question 21

Describe glucose uptake during the fed state in the liver

Answer 21

liver takes up glucose because insulin activates hexokinase which lowers [glucose]ic creating a gradient favouring glucose movement into the cells.

Question 22

Describe glucose movement during the fasted state

Answer 22

liver synthesises glucose via glycogenolysis and gluconeogenesis, increasing [glucose]ic creating a gradient favouring glucose movement out of the cells into the blood.

Question 23

What is the half-life of insulin

Answer 23

5 minutes

Question 24

What happens to the insulin bound receptors once insulin action is complete

Answer 24

insulin-bound receptors are internalised by endocytosis

Question 25

Name stimuli which increase insulin

Answer 25

``` High Blood glucose Amino acid Glucagon Incretin hormones Vagal nerve activity ```

Question 26

Name stimuli which inhibit insulin

Answer 26

Low blood glucose Somatostatin (GHIH) Sympathetic Stress e.g. hypoxia

Question 27

Between IV and oral glucose which would have the largest insulin response

Answer 27

• Oral loading of same amount of glucose   insulin by both direct effect on  cells and vagal stimulation of  cells, plus incretin effects

Question 28

What type of hormone is glucagon

Answer 28

Peptide hormone and produced by 1-cells of the pancreatic islets cells

Question 29

Glucagon mainly acts on what organ

Answer 29

Liver

Question 30

What is the plasma half-life of glucagon

Answer 30

5-10 minutes and degraded by liver

Question 31

Name the main actions of Glucagon

Answer 31

Opposes action of glucagon Increased glycogenolysis Increases gluconeogenesis Formation of ketones from fatty acids

Question 32

Following a meal rich in proteins why is there an increase in insulin and glucagon

Answer 32

The rise in amino acids stimulates insulin secretion which promotes an increase in amino acid uptake and promotes decrease in plasma glucose  inappropriate and can lead to hypoglycaemia • Rise in plasma amino acids also stimulates the secretion of glucagon which tends to promote an increase in plasma glucose

Question 33

Stimuli that promote glucagon release

Answer 33

* Low blood glucose * High amino acids to prevent hypoglycaemia * Sympathetic innervation and adrenaline B2 effects * Cortisol * Stress e.g. exercise, infection

Question 34

Stimuli that inhibit glucagon release

Answer 34

* Glucose * FFA * Insulin * Somatostatin

Question 35

Describe the parasympathetic stimulation of Islet cells

Answer 35

Insulin increase as well as glucagon in anticipation of digestion

Question 36

Describe the sympathetic stimulation of islet cells

Answer 36

Increase in glucagon, epinephrine and inhibition of insulin

Question 37

Name hormones that regulate muscle glycogenlysis

Answer 37

Epinephrine

Question 38

Name hormones that regulate liver glycogenolysis

Answer 38

Glucagon | Epinphrine

Question 39

Name hormones that regulate Gluconeogenesis

Answer 39

Glucagon

Question 40

Name hormones that regulate inhibition of glucose uptake

Answer 40

Cortisol and GH

Question 41

Name hormones that regulate lipolysis

Answer 41

Epinphrine

Question 42

Name hormones that regulate protein catabolism

Answer 42

Cortisol

Question 43

Somatostatin in secreted by what cell

Answer 43

D-cells of the pancreas and hypothalamus (GHIH)

Question 44

What is the main actions of Somatostatin

Answer 44

Inhibit activity in the GI tracts Slow down absorption of nutrients to prevent exaggerated peaks in plasma concentration Supress release of insulin and glucagon in paracrine fashion GHIH it inhibits secretion of GH from the anterior pituitary

Question 45

What is the effect of exercise on blood glucose

Answer 45

Entry of glucose into skeletal muscle is increased. Even in the absence of insulin Muscle sensitivity to insulin increases which causes an increase in insulin independent GLUT 4 transporters

Question 46

What is the molecular weight of glucose

Answer 46

180

Question 47

How do you work out the blood glucose in mM

Answer 47

Divide blood glucose after fasting by (180/18)

Question 48

Name complications of diabetes

Answer 48

* Hyperglycaemia * Retinopathy * Neuropathy * Nephropathy * Cardiovascular Disease