Calcium

Question 1

A decrease in extracellular calcium….increases or decreases permability to sodium?

Answer 1

increases (sodium gets in) causing hyperexcitability leading to tetany and seizure

Question 2

An increase in extracellular calcium can cause a patient to become what?

Answer 2

sluggish, constipated, fatigued

Question 3

what percentages of calcium are
free ionized…
bound to plasma proteins…
diffusable through capillaries but not ionized…

Answer 3

50%
41%
8%

Question 4

how much calcium is inorganelles (inside the cell)

Answer 4

1%

Question 5

bone stores calcium, what else is stored there?

Answer 5

phosphate (85% of the body)

Question 6

you need 1000mg/day of calcium and phosphate. what increases the reabsorption of calcium?

Answer 6

vitamin D

Question 7

what fine tune regulates the net loss of calcium in the kidneys?

Answer 7

PTH hormone

Question 8

phosphate excretion is regulated by…

Answer 8

an overflow mechanism

Question 9

for the best efficacy but less total absoprption, for osteoporosis we give calcium with what other cation?

Answer 9

Mg2+

Question 10

we want calcium to precipitate only in bone and not tissues, and are used by what cells?

Answer 10

osteoblasts

Question 11

what are osteocytes?

Answer 11

osteoblasts encased in bone

Question 12

do you need osteoclasts to function for obsteoblasts to do their normal job?

Answer 12

yep

Question 13

what is a potent inhibitor of calcium precipitation?

Answer 13

pyrophosphate

Question 14

what do osteoblasts ONLY respond to….

PTH, Vitamin D, or osteoblasts?

Answer 14

osteoblasts

Question 15

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…

Answer 15

too high…promotes bone resorption

too low…promotes bone resorption mineralization

Question 16

what are the 3 function of 1,25 dihydro D3 which is made in the kidneys from 25OH in the liver?

Answer 16

1. promotes serum ca2+ reabsorption
2. promotes GI calcium absoprtion
3. promotes renal reabsoprtion

Question 17

vitamin D’s effect on its own is weak, and needs Phosphate…where is most calcium reabsoprtion (99% occuring)

Answer 17

in the gut

Question 18

what are the 3 types of cells in the parathyroid?

Answer 18

chief cells
oxyphil cells: absent in kids
RBC’s

Question 19

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 ________

Answer 19

decreasing, increasing
(because PTH regulates other body functions to bring Ca2+ back up)
NOT REGULATED BY PITUITARY

Question 20

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?

Answer 20

vitamin D
(the absorption of phosphate does not need vitamind D, only calcium needs it)

Question 21

how does PTH specifically work on bone to release Ca2+

Answer 21

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.

Question 22

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?

Answer 22

to keep more free ionized calcium available. calcium binds and becomes inactive when bound to phosphate.

Question 23

In the young, calcitonin is more powerful than in adults at lowering serum Ca2+ concentrations how?

Answer 23

by lowering osteolytic activity