Night before Oral Exam! Flashcards

(18 cards)

1
Q

Calcium in extracellular fluid must be very tightly regulatd: why?

A

close to level at which it will precipitate.

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2
Q

how much serum Ca is free vs. bound?

A

50/50

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3
Q

consequences of hypocalcemia?

A

long-term: bone weakening. shorter term: arrythmias due to lowered threshold, increased muscle excitability.

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4
Q

consequences of hypercalcemia?

A

decreased muscle excitability, increased BP.

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5
Q

minority of reabsorption of Ca in the nephron is done where and how?

A

in prox tubule and loop, paracellular.

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6
Q

majority of Ca reabsorption is done where?

A

distal tubule. active transcellular route. prime site of regulation. via calbindin.

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7
Q

why calbindin?

A

intracellular Ca needs to be kept low, therefore bind it to protein to transport

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8
Q

relationship between Na and Ca reabsorption in the prox tubule and loop?

A

they are transported together. due to + lumen voltage, they go paracellularly.

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9
Q

relationship between Na and Ca reabsorption in the distal tubule?

A

they oppose each other: if too much Na reabsorption in the cell, too positive for Ca entry as well.

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10
Q

Thiazide diuretics block what transporter, and do what to Ca levels?

A

block the Na/Cl cotransporter, and can lead to hyper Ca.

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11
Q

Will binding of Ca to albumin increase or decrease at alkalotic pH?

A

increase. normally albumin binds H and Ca, and if there is less H there is more binding capacity for Ca. this leads to a decrease in free Ca.

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12
Q

chronic metabolic acidosis does what to Ca levels?

A

inhibits Ca reabsorption directly.

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13
Q

the distribution of phosphate between cells and extracellular fluid is dependent upon what?

A

acid/base balance and carbohydrate status. alkalosis results in P shift INTO cells, acidosis results in P shift OUT of cells

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14
Q

where is most of P reabsorped?

A

in Prox tubule in cotransport with Na.

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15
Q

what sill stimulate a releae of PTH?

A

a decrease of plasma Ca.

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16
Q

how does a decrease of plasma Ca lead to a release of PTH?

A

CaSR receptor: inhibits release of PTH until a state of hypocalcemia. Then inibibtion is lifted.

17
Q

4 actions of PTH?

A

increases Ca reabsorption. decreases P reabsorption. induces Ca and Pi release from bone. converts Vit D into active form

18
Q

how does the kidney guard against stones in lumen or interstitium?

A

sites of regulation of reabsprption for 3 minerals (P, Ca, Mg) are different. Pi = prox tubule, Ca = distal tubule, Mg = early part of distal tubule.
Also: well placed CaSRs on lumen side of TALH. increase in local Ca will yield decreased Ca reabsorption.