Calcium Homeostasis

Question 1

What has 99% of our calcium?

Answer 1

bones

Question 2

where is 0.1% of our calcium?

Answer 2

extracellular

Question 3

where is 0.9% of our calcium?

Answer 3

mitochondria and sarcoplasmic reticulum

Question 4

nearly half of calcium found in the ECF is bound to ….

Answer 4

protein

Question 5

Where is the other half of calcium in the ECF (the half that is not bound to protein)

Answer 5

free in solution

physiologically active

Question 6

how much (value) calcium is found in plasma?

Answer 6

2.2-2.6mM

Question 7

What does calcium have a high affinity for?

Answer 7

proteins

small positive charge to large negative charge

Question 8

Physiologically active Calcium in the plasma accounts for about 50% of plasma calcium. Therefore its value is approx

Answer 8

1.2mM

Question 9

binding capacity of plasma proteins changes with what?

Answer 9

pH

Question 10

binding capacity of plasma proteins increases under what conditions?

Answer 10

alkalotic

Question 11

what happens to pH if you hyperventilate?

Answer 11

rises

alkalosis

Question 12

What happens (with regards to calcium) when pH rises?

Answer 12

More proteins bind the calcium precipitating hypocalcaemia

Question 13

In acidosis, plasma protein binding capacity is reduced therefore

Answer 13

free calcium in the plasma rises

Question 14

bone will release calcium to maintain what plasma level of calcium?

Answer 14

1.2mmol

Question 15

what are the two key hormones that act to increase calcium in the plasma?

Answer 15

parathyroid hormone

calcitriol

Question 16

what is calcitriol?

Answer 16

active from of vitamin D3

Question 17

Why cant you have your parathyroid glands removed?

Answer 17

you lose your ability to control calcium homeostasis

Question 18

Parathyroid hormone is released in response to what?

Answer 18

low calcium in plasma

Question 19

what effect does vitamin D3 have on plasma calcium?

Answer 19

increases it

Question 20

what does vitamin D3 complement the actions of?

Answer 20

parathyroid hormone

Question 21

when calcium plasma is low - and increase in PTH leads to an increase in ………. - which leads to increased ……. ……….. .. …….

Answer 21

calitriol

intestinal absorption of calcium

Question 22

increase in levels of calcium inhibits

Answer 22

PTH

Question 23

What three major processes do calcitriol binding to nuclear receptors regulate?

Answer 23

increases absorption of Ca from gut

facilitates renal absorption of Ca

Mobilises calcium stores in bone by stimulating osteoclast activity

Question 24

Vitamin D3 acts to increase ………..

Answer 24

plasma calcium

Question 25

Vitamin D deficiency - PTH maintains plasma Ca by taking Ca from

Answer 25

bones

rickets/ oestomalacia

Question 26

vitamin D3 deficiency will result in reduced …… as well as …….

Answer 26

calcium

phosphate