Calcium Flashcards
A decrease in extracellular calcium….increases or decreases permability to sodium?
increases (sodium gets in) causing hyperexcitability leading to tetany and seizure
An increase in extracellular calcium can cause a patient to become what?
sluggish, constipated, fatigued
what percentages of calcium are
free ionized…
bound to plasma proteins…
diffusable through capillaries but not ionized…
50%
41%
8%
how much calcium is inorganelles (inside the cell)
1%
bone stores calcium, what else is stored there?
phosphate (85% of the body)
you need 1000mg/day of calcium and phosphate. what increases the reabsorption of calcium?
vitamin D
what fine tune regulates the net loss of calcium in the kidneys?
PTH hormone
phosphate excretion is regulated by…
an overflow mechanism
for the best efficacy but less total absoprption, for osteoporosis we give calcium with what other cation?
Mg2+
we want calcium to precipitate only in bone and not tissues, and are used by what cells?
osteoblasts
what are osteocytes?
osteoblasts encased in bone
do you need osteoclasts to function for obsteoblasts to do their normal job?
yep
what is a potent inhibitor of calcium precipitation?
pyrophosphate
what do osteoblasts ONLY respond to….
PTH, Vitamin D, or osteoblasts?
osteoblasts
if the production of 1,25 Dihydro D3 in the kidneys is not well regulated, what are the effects of it being…
too high…
too low…
too high…promotes bone resorption
too low…promotes bone resorption mineralization
what are the 3 function of 1,25 dihydro D3 which is made in the kidneys from 25OH in the liver?
- promotes serum ca2+ reabsorption
- promotes GI calcium absoprtion
- promotes renal reabsoprtion
vitamin D’s effect on its own is weak, and needs Phosphate…where is most calcium reabsoprtion (99% occuring)
in the gut
what are the 3 types of cells in the parathyroid?
chief cells
oxyphil cells: absent in kids
RBC’s
a man gets no sunlight and doesnt eat any foods with vitamin D in it. you would expect his calcium levels to be_________, and his PTH to respond by ________
decreasing, increasing
(because PTH regulates other body functions to bring Ca2+ back up)
NOT REGULATED BY PITUITARY
ok so when serum Ca2+ is low, PTH is stimulated using what molecule it told the kidneys to synthesize what as its helper to reabsorb Ca2+ from the gut?
vitamin D (the absorption of phosphate does not need vitamind D, only calcium needs it)
how does PTH specifically work on bone to release Ca2+
well, calcium is stored in bone fluid, and PTH
in the slow phase….use osteoclasts
in the fast phase…Ca2+ pump that keeps Ca+ in stops working, and releases it.
when PTH stimulates an increase in calcium and phosphate absorption in the GI, why in the kidneys does it only reabsorb Calcium, and actually DUMPS phosphate?
to keep more free ionized calcium available. calcium binds and becomes inactive when bound to phosphate.
In the young, calcitonin is more powerful than in adults at lowering serum Ca2+ concentrations how?
by lowering osteolytic activity
