The Endocrine Pancreas

Question 1

What two centres of the brain govern food intake?

Answer 1

Feeding centre and satiety centre (both in the hypothalamus)

Question 2

What two theories govern food intake?

Answer 2

1. Glucostatic theory

2. Lipostatic theory

Question 3

What does glucostatic theory state?

Answer 3

Food intake is determined by blood glucose concentrations - as [BG] increases the drive to eat decreases

Question 4

What does the lipophilic theory state?

Answer 4

Food intake is determined by fat stores - as fat stores increase, the drive to eat decreases

Question 5

What peptide hormone plays a role in depressing feeding activity?

Answer 5

Leptin

Question 6

How can obesity arise from the threories of food intake?

Answer 6

Disruption of the pathways

Question 7

What three categories of energy output are there?

Answer 7

1. Cellular work
2. Mechanical work
3. Heat loss

Question 8

What is the only type of energy output we can regulate?

Answer 8

Mechanical

Question 9

What is the definition of metabolism?

Answer 9

Integration of all biochemical reactions in the body

Question 10

What three elements comprise metabolism?

Answer 10

1. Extracting energy from nutrients in food
2. Storing that energy
3. Utilising that energy for work

Question 11

What two metabolic pathways are there?

Answer 11

Anabolic and catabolic

Question 12

What phase of metabolism do we enter after eating?

Answer 12

Absorptive phase - anabolic

Question 13

What phase of metabolism do we enter between meals and overnight?

Answer 13

Post-absorptive phase (fasting) - catabolic

Question 14

What is an obligatory glucose user? Give an example?

Answer 14

An organ that can only utilise glucose as a respiratory substrate

Question 15

State the normal range of blood glucose

Answer 15

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

Question 16

What do alpha cells secrete in the pancreas?

Answer 16

Glucagon (peptide hormone)

Question 17

What is the primary action of glucagon?

Answer 17

Raise blood glucose by stimulating the liver to undergo glycogenolysis

Question 18

What is the half life of glucagon?

Answer 18

5-10 mins

Question 19

What hormone is secreted by the beta cells?

Answer 19

Insulin

Question 20

What is the primary action of insulin?

Answer 20

To decrease blood glucose

Question 21

What hormone do delta cells secrete?

Answer 21

Somatostatin

Question 22

What hormone do F cells secrete?

Answer 22

Pancreatic polypeptide (functionally irrelevant)

Question 23

Outline the sequence of events that insulin instigates to decreased blood glucose

Answer 23

1. Actives tyrosine kinase receptors
2. Stimulates mobilisation of specific GLUT-4 receptors which reside in the cytoplasm of unstimulated muscle and adipose cells

Question 24

What are the additional secondary effects of insulin?

Answer 24

1. Glycogen synthesis
2. Increase uptake of amino acids
3. Inhibits proteolysis
4. Increases TAG synthesis
5. Inhibits gluconeogenesis
6. Permissive effect on growth hormone

Question 25

What tissues are insulin sensitive?

Answer 25

Muscle and fat

Question 26

Other tissues use other glucose transporters to uptake glucose; give a few examples

Answer 26

GLUT-1 - brain, kidneys and RBCs GLUT-2 - Pancreas and liver GLUT-3 - similar to GLUT-1

Question 27

List stimuli that increase insulin release

Answer 27

1. Increase in [BG] 2. Increase [Amino acid]plamsa 3. Glucagon 4. Other (incretin) hormones increasing GI motility/secretion 5. Vagal nerve activity

Question 28

List stimuli that inhibit glucose release

Answer 28

1. Low [BG] 2. Somatostatin 3. Sympathetic alpha2 effects 4. Stress e.g. hypoxia

Question 29

What receptors does glucagon work on?

Answer 29

GPCR linked to adenyl cyclase which activate cAMP to phosphorylate liver enzymes

Question 30

What stimuli cause secretion of glucagon?

Answer 30

1. Low [BJG] 2. High [AAs] 3. Sympathetic innervation 4. Cortisol 5. Stress e.g. exercise and infection

Question 31

What inhibits the release of glucagon?

Answer 31

1. Glucose 2. FFAs and ketones 3. Insulin 4. Somatostatin

Question 32

What is the main action of somatostatin?

Answer 32

Inhibits activity in the GI tract

Question 33

How can synthetic somatostatin be used clinically?

Answer 33

In the treatment of life-threatening diarrhoea associated with pancreatic tumours