clinical calcium homeostasis - physiology Flashcards
What are the functions of calcium
Bone formation
Cell division and growth
Muscle contraction
Neurotransmitter release from vesicles
What state does calcium have to be to be filtered by the glomerulus
Free calcium
why is a lot of calcium excreted
Because it forms compounds of insoluble salts
What proportion of calcium is bound in plasma
40% bound
What proportion of calcium is complexed (non-ionised)
15%
what proportion of calcium is ionised (free)
45%
What is the normal range of calcium
2.2-2.6 mmol/Litre
what is the effect of acidosis on calcium in the plasma
Increases free (ionised) calcium in the plasma due to less hydrogen ions being free as more are bound to complexes allowing for calcium to unbind
What is the effect of albumin on free calcium
Increased albumin decreases free calcium
How is free calcium calculated
Adjust calcium by 0.1 mmol/Litre for each 5g per litre reduction in albumin from 40g/l
Mr Bloggs has a Calcium of 2.55mmol/L, his albumin is 30g/L. What is his corrected calcium?
2x5g reduction in plasma from 40g/L therefore corrected calcium is 2.55 +0.2 mmol/l = 2.75 mmol/litre
How many parathyroid glands and what kind of cells are they
4 parathyroid glands - 2 types of cells:
Chief cells and oxyphils cells
What do chef cells of the parathyroid glands secrete
PTH - parathyroid hormone
What is the effect of decreased calcium in the plasma and describe how it occurs
Chief cells respond directly as the low levels in the plasma of calcium are transmitted through the calcium sensing receptor CaSR - this causes a increased secretion of PTH by the chief cells
What is the effect of PTH on reabsorption of calcium
It promotes reabsorption from the renal tubules and bone
