Calcium homeostasis Flashcards
What is main store of calcium?
Skeleton- 1200g
What is lvl of total serum calcium?
2.4 mmol/L
State 6 functions of calcium?
1) Muscle contraction
2) Neurotransmitter release- Ca2+ into synaptic terminal
3) Conduction system of the heart – Ca2+ instead of Na+ to depolarise
4) Myocardial contraction- plateau phase
5) Clotting cascade- cofactor in most activation steps
6)Bone integrity
How is calcium distributed in blood? (3)
Ionised– important for cell function
Protein-bound– bound to albumin
Complexed– e.g. with citrate and phosphate
Daily recommended intake calcium?
1000mg
During alkalosis how is calcium distribution altered?
Alkalosis- hyperventilation
High pH- albumin binds Ca2+
Lower ionised calcium
Increased protein bound
During acidosis how is calcium distribution altered?
Ionised Ca2+ increased
Lower protein bound
Where is calcium absorbed?
What does it require?
Absorbed duodenum and jejunum
Requires vit D
Where can calcium be released from?
Bone
What occurs if increase Ca2+ lvls detected?
1) Sensed by chief cells in parathyroid gland
2a) Decrease osteoclast activity- decrease bone reabsorption
2b) Decrease vit D activation- decrease calcium uptake from duo
3) Decrease Ca2+
What occurs if decrease Ca2+ lvls detected?
1) Sensed by chief cells in parathyroid gland
2) Increased PTH secretion
3a) Increase osteoclast activity- increase bone resorption
3b) Increased vit D activation- increase calc uptake from duo
What senses low calcium levels?
Chief cells in parathyroid gland
