23.3 Calcium Balance Flashcards
(45 cards)
What happens if Ca levels rise too high above normal?
- nervous system becomes progressively damaged.
- constipation, and sluggish reflexes
- above 12mg/dl
What happens if Ca levels fall too low below normal?
- nervous sytem become overexcited
Where is the majority of Ca stored in teh body?
bones. 1% in the cells/organells. 0.1% in ECF
Where is the majority of phosphate stored in the body?
bones. 15% in cells. 1% in ECF
Which system is much more tolerant to varying levels of concentration?
phosphate, allows multiple changes without having large effect. Ca has large effect with minor changes
What are the effects of hypocalcemia?
- increased excitability of nervous system
2. seizures, seen in the hand with carpopedal spasm
When can tetany become lethal?
at 4mg/dl, onset at
how much of Ca intake from diet is absorbed?
only 10%. the rest is excreted. Poor absorption rate in the GI, is improved with Vitamin D
What hormone can increase the excretion of phosphate through renal system?
parathyroid hormone. required for survival
How much calcium is reabsorbed from the filtrate?
99%, minimal amount is secreted in urine
What is present that inhibits the precipitation of hydroxyapatite crytsals, and prevents formation of bone?
pyrophosphate
WHat is the benefit of keeping hydroxyapatite in an amorphous (noncrystalline form)?
this allows for faster reabsorption into ECF for migration to different tissues when needed
When will calcium salts precipitate to other tissues?
normal conditions, but calcium salt deposition inhibitor factors disappear
How rapidly can [Ca] return to normal after large amounts are removed from body fluids?
return to normal in 30 minutes
How rapidly can [Ca] return to normla after large amounts are injected IV?
return to normal in 30-60 minutes
What is responsible for providing the body the ability to rapidly alter [Ca] levels in circulating fluids?
exchangeable calcium present in all cell types
What is the active form of Vitamin D?
1,25-dihydroxycholecalciferol
What does the active form of Vitamin D do?
- increase Ca and phosphate absorption into ECF from the intestine, kidneys, and bones
Vit D binds its receptor as what type?
binds as hormone that activates a DNA region
What complex does Vit D form in order to activate trasncription?
binds with retinoid X-factor to initiate transcription. is possible to inhibit trasnscirption
The absence of Vit D can severely (negatively) affect what other hormone?
PTH, becasue there is reduced calcium transport through cellular membranes.
What is the difference of super high Ca presence versus small amount of Ca presence?
- high amount= absorption into bone
2. low amounts= bone calcification
Excess activity of the parathyroid hormone causes what condition?
- secretion of calcium salts from bones, leading to hypercalcemia
Under activity of the parathyroid hormone causes what condition?
- reduced secretion of calcium salt from bone, leading to hypocalcemia
