calcium homeostasis Flashcards
physiological functions of ionic Ca
action potentials
muscle contraction
cell division
secondary haemostasis
cell communication
physiological functions of bound Ca
biomaterial for bones and teeth
T/F 99% of calcium is stored in the body as calcium phosphate in bones and teeth
T
what are the two factors that can regulate blood calcium levels
PTH
vit D
what is the active form of vitamin D
calcitriol - synthesised in the liver
what is the third regulator of calcium blood levels
calcitonin - formed in the thyroid gland
not a very good regulator
what does Vit D do
facilitates the absorption of calcium and phosphate from food in the GI tract > this activates osteoblasts > triggering mineralisation and bone remodelling
> elevates the amount of calcium and phosphate in the blood
what does PTH do
stabilises blood calcium levels > primarily by activating osteoclasts and therefore bone demineralisation
> elevates calcium levels but decreases phosphate levels
where can the calcium sensitive receptors be found
primarily in renal tubular cells and in the parathyroid gland
ie in hypercalcaemia , this inhibits the release of PTH but in turn releases calcitonin > calcitonin ensures that less calcium is absorbed from food
» it also inhibits osteoclast activity and therefore the release of calcium and phosphate from the bones and facilitates their excretion via the kidneys
function of calcitonin
lowers calcium and phosphate blood levels
function of PTH
raises blood calcium by :
increasing osteoclast activity in bones (reabsorbing from bones)
increasing calcium absorption from the gut
increasing calcium absorption from the kidneys
increasing vitamin D activity
function of vitamin D
it acts to increase calcium absorption from the intestine
> PTH acts on vit D to convert it into active forms (calcitriol)
