Calcium Homeostasis Flashcards
what are the five roles of calcium in the body?
- signalling
- blood clotting
- apoptosis
- skeletal strength
- membrane excitability
what can happen in extreme cases of hypocalcaemia?
tetany - if spreads to larynx and respiratory muscles, asphyxiation
what can happen in extreme cases of hypercalcaemia?
trigger cardiac arrhythmias
where is 99% of the calcium in the body?
in tha bonez
what percentage of calcium in the body is free in solution and physiologically active?
0.05%
in what form is the calcium stored in the calcified extracellular matrix of the bone?
hydroxyapatite
Ca10(PO4)6(OH)2
which other ion also needs to be kept in homeostasis to maintain calcium balance?
phosphate
what is the tight range in which calcium concentrations in the plasma are kept?
2.2-2.6mM
what happens to the binding capacity of plasma proteins in acidic conditions?
it decreases
which activity can raise plasma pH?
hyperventilation
what does alkalosis do to the amount of protein bound calcium?
increases amount of protein bound calcium
why does acidosis result in increased free plasma calcium?
the increased H+ ions displace the calcium ions bound to the protein
what are the two key hormones working to increase plasma calcium?
parathyroid hormone (PTH) and calcitriol (active form of vit D)
what is the normal number of parathyroid glands?
4
can the parathyroid glands be removed?
no they’re essential for life (can take some out but have to leave at least one)
what stimulates PTH release?
reduction in free plasma calcium
what are the five ways in which PTH increases free plasma calcium?
- stimulates osteoclasts to increase resorption (release) of calcium and phosphate in bone
- inhibits osteoblasts, reducing calcium deposition in bone
- increases reabsorption of calcium from the kidney tubules
- increases renal excretion of phosphate
- stimulates kidneys to synthesise calcitriol
is parathyroid hormone a peptide, amine or steroid hormone?
peptide
is calcitriol a peptide, amine or steroid hormone?
steroid
what vitamin is a precursor for calcitriol production?
vitamin D
in which two places does calcitriol production take place?
liver and kidneys
what are some dietary sources of vitamin D?
fatty fish (e.g. mackerel and tune), fish liver oils, egg yolks
what are the three actions of calcitriol?
- increase absorption of calcium from the gut
- facilitates renal absorption of calcium
- mobilises calcium in bone by stimulating osteoclast activity
which of these hormones’ production does prolactin stimulate?
calcitriol
