MEH Revision

Question 1

What are the uses of the pentose phosphate pathway?

Answer 1

Produces C5 ribose used for DNA synthesis

Produces NADPH - important for re-oxidising glutathione- an important protective mechanism

Question 2

What are Heinz Bodies and why are they formed?

Answer 2

They are Hb + other protein aggregates that form because they become cross-linked by disulphide bonds from oxidative damage.

It causes premature destruction of RBCs and hemolysis –> hemolytic anaemia

Question 3

What are the excitatory neurones in the hypothalamus that stimulate appetite?

Answer 3

NPY (neuropeptide Y)

agouti-related peptide AgRP

Question 4

What can POMC be cleaved into?

Answer 4

B-endorphin
Alpha-MSH
ACTH
*why people with addisons skin goes darker, producing more POMC to try and get more ACTH)

Question 5

What does gherlin do?

Answer 5

It is released from the wall of an empty stomach
Activates stimulatory neurones in the arcuate nucleus - increase appetite
Stretch of the stomach wall inhibits gherlin release

Question 6

What does leptin do?

Answer 6

Leptin is released from adipocytes and causes inhibition of excitatory neurones - stimulates inhibitory neurones

Question 7

What is the link between leptin and obesity?

Answer 7

It is thought that obese people don’t feed back and stimulate inhibition

Question 8

What are the WHO criteria for metabolic syndrome?

Answer 8

Central obesity
BMI >30kg/m2
Blood pressure >140/90 mmHg
Triglyerides > 1.7 mmol/L
HDL cholesterol <0.9 mmol/L 
Glucose fasting / 2 hour after glucose load > 7.8 mmol/L

Question 9

What are the major factors contributing to insulin resistance?

Answer 9

Sedentary lifestyle

Obesity

Question 10

Where in the hypothalamus is the control of appetite?

Answer 10

Arcuate nucleus

Question 11

Where is thyrotrophin releasing hormone (TSH) released from in the hypothalamus?

Answer 11

The dorsomedial nucleus - this is influenced by levels of T3 and T4 (negative feedback)

Question 12

What is the name of the hormone that is released in the hypothalamus and acts on the anterior pituitary to release thyroid hormone?

Answer 12

TRH - thyrotrophin releasing hormone

Question 13

What does TRH (thyrotrophin releasing hormone do)

Answer 13

Causes an increase in thyroid stimulating hormone

Question 14

Where does TSH travel to to have an effect

Answer 14

The follicular cells

Question 15

What does trophic effect mean?

Answer 15

Trophic hormone is a hormone that has a growth effect, hyperplasia or hypertrophy on the tissue it is stimulating.

Question 16

What are the trophic effects of TSH on the thyroid?

Answer 16

Increased vascularity
Increase in size/number of follicle cells
Therefore an lead to enlarged goitre - may be overactive or under active

Question 17

What are the effects of T3/T4 on the body?

Answer 17

Increase metabolic rate:
Increased glucose uptake and metabolism
Stimulise mobilisation and oxidation of fatty acids
Stimulate protein metabolism

Question 18

Are the effects of T3/T4 catabolic or anabolic?

Answer 18

Catabolic - increased BMR, increased heat production (UCPs), increased O2 consumption

Question 19

Where do T3 and T4 act?

Answer 19

Within the cell

Interacting with high affinity receptors in the nucleus (and possibly mitochondria)

Question 20

What is hashimotos disease?

Answer 20

Auto-immune disease

Affecting 1% of population

Question 21

What do you treat hyperthyroidism with?

Answer 21

Carbimazole - stops the iodine attaching onto thyrglobulin

Question 22

What are the major components of hydroxyapatite crystals?

Answer 22

Calcium

Phosphate

Question 23

Where would you find hydroxyapatite crystals?

Answer 23

In the mineral in bone

Question 24

What regulates calcium turnover?

Answer 24

parathyroid hormone, calcitriol and to a lesser extent calcitonin

Question 25

Where do the hormones regulating calcium (PTH, calcitriol and calcitonin) act?

Answer 25

GI tract, kidneys and bone

Question 26

What is the active form of vitamin D called?

Answer 26

Calcitriol

Question 27

What is the hormonal regulation of calcium?

Answer 27

Calcium binds to the G protein coupled receptor on the PTH This causes phospholipase C which causes inhibition of adenylyl cyclase which leads to reduced cAMP and therefore reduced PTH release

Question 28

What does the anterior pituitary produce?

Answer 28

``` TSH (thyroid stimulating hormone) ACTH Growth hormone LH and FSH Prolactin ```

Question 29

When is cortisol released?

Answer 29

In response to physical (temperature/pain), chemical (hypoglycaemia) and emotional stressors

Question 30

What are the catecholamines synthesised from?

Answer 30

A series of enzyme catalysed steps that convert Tyrosine to Dopa and then Dopamine. Dopamine is then converted to noradrenaline and noradrenaline to adrenaline by methylation. Tyrosine --> dopa --> dopamine --> Noradrenaline --> adrenaline

Question 31

What is produced in the adrenal cortex? (Think salt sugar sex)

Answer 31

Aldosterone Cortisol Androgens

Question 32

What is produced in the adrenal medulla?

Answer 32

Catecholamines e.g. Adrenaline and noradrenaline

Question 33

What would cause over-secretion of catecholamines?

Answer 33

An adrenal tumour e.g. Phaeochromocytoma