Endocrine control of calcium and phosphate

Question 1

List 7 major physiological roles of calcium.

Answer 1

1. Bone mineralisation
2. Teeth enamel and present in saliva
3. Skeletal, cardiac, and smooth muscle contraction
4. Membrane potential and depolarisation
5. All processes that involve exocytosis, including neurotransmitter and hormone release
6. Enzyme co-factor, e.g. coagulation factors
7. Intracelular second messenger

Question 2

What is the weight range of total body calcium?

Answer 2

1 - 2kg

Question 3

What percentage of total body calcium is found in the skeleton?

Answer 3

99%

Question 4

What is the normal range of plasma total calcium?

Answer 4

2.2 - 2.6 mmol/l

Question 5

List the 3 forms of calcium found in the plasma, with percentages.

Answer 5

Free ionised calcium (Ca2+)(50%)

Bound to anions, e.g. phosphate (10%)

Bound to plasma proteins, e.g. albumin (40%)

Question 6

Which 3 factors affect blood calcium concentration?

Answer 6

Concentration of plasma proteins
Concentration of anions
pH

Question 7

If the concentration of anions increases, in what way will this affect Ca2+ levels and why?

Answer 7

Ca2+ levels will decrease because more will bind to the anions

Question 8

In what way does acidaemia affect Ca2+ levels and why?

Answer 8

Increase Ca2+ levels because hydrogen ions compete with Ca2+ to bind to albumin

Question 9

In what way does alkalaemia affect Ca2+ levels and why?

Answer 9

Decrease Ca2+ levels because more Ca2+ can freely bind to albumin without needing to compete with hydrogen ions

Question 10

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