Calcium Homeostasis

Question 1

what are the five roles of calcium in the body?

Answer 1

1. signalling
2. blood clotting
3. apoptosis
4. skeletal strength
5. membrane excitability

Question 2

what can happen in extreme cases of hypocalcaemia?

Answer 2

tetany - if spreads to larynx and respiratory muscles, asphyxiation

Question 3

what can happen in extreme cases of hypercalcaemia?

Answer 3

trigger cardiac arrhythmias

Question 4

where is 99% of the calcium in the body?

Answer 4

in tha bonez

Question 5

what percentage of calcium in the body is free in solution and physiologically active?

Answer 5

0.05%

Question 6

in what form is the calcium stored in the calcified extracellular matrix of the bone?

Answer 6

hydroxyapatite

Ca10(PO4)6(OH)2

Question 7

which other ion also needs to be kept in homeostasis to maintain calcium balance?

Answer 7

phosphate

Question 8

what is the tight range in which calcium concentrations in the plasma are kept?

Answer 8

2.2-2.6mM

Question 9

what happens to the binding capacity of plasma proteins in acidic conditions?

Answer 9

it decreases

Question 10

which activity can raise plasma pH?

Answer 10

hyperventilation

Question 11

what does alkalosis do to the amount of protein bound calcium?

Answer 11

increases amount of protein bound calcium

Question 12

why does acidosis result in increased free plasma calcium?

Answer 12

the increased H+ ions displace the calcium ions bound to the protein

Question 13

what are the two key hormones working to increase plasma calcium?

Answer 13

parathyroid hormone (PTH) and calcitriol (active form of vit D)

Question 14

what is the normal number of parathyroid glands?

Answer 14

4

Question 15

can the parathyroid glands be removed?

Answer 15

no they’re essential for life (can take some out but have to leave at least one)

Question 16

what stimulates PTH release?

Answer 16

reduction in free plasma calcium

Question 17

what are the five ways in which PTH increases free plasma calcium?

Answer 17

1. stimulates osteoclasts to increase resorption (release) of calcium and phosphate in bone
2. inhibits osteoblasts, reducing calcium deposition in bone
3. increases reabsorption of calcium from the kidney tubules
4. increases renal excretion of phosphate
5. stimulates kidneys to synthesise calcitriol

Question 18

is parathyroid hormone a peptide, amine or steroid hormone?

Answer 18

peptide

Question 19

is calcitriol a peptide, amine or steroid hormone?

Answer 19

steroid

Question 20

what vitamin is a precursor for calcitriol production?

Answer 20

vitamin D

Question 21

in which two places does calcitriol production take place?

Answer 21

liver and kidneys

Question 22

what are some dietary sources of vitamin D?

Answer 22

fatty fish (e.g. mackerel and tune), fish liver oils, egg yolks

Question 23

what are the three actions of calcitriol?

Answer 23

1. increase absorption of calcium from the gut
2. facilitates renal absorption of calcium
3. mobilises calcium in bone by stimulating osteoclast activity

Question 24

which of these hormones’ production does prolactin stimulate?

Answer 24

calcitriol