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Physiology II > Calcium Balance (Lec 18) > Flashcards

Calcium Balance (Lec 18) Flashcards

1
Q

Increases in calcium ions above normal cause progressive depression of what?

A

nervous system

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2
Q

symptoms of hypercalemia tend to appear when the blood calcium level rises above ___ mg/dl

A

12

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3
Q

Decreases in calcium storage cause the nervous system to become more ___

A

excited

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4
Q

___ % of the total body calcium is in the extracellular fluid

A

0.1

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5
Q

___ % of the calcium in the body is in the cells and organelles, the rest is stored in ___

A

1; bones

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6
Q

Breakdown the store of phosphate in bones, cells and ECF

A

bones: 85 %
cells: 14-15%
ECF: less than 1%

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7
Q

What are the two forms of inorganic phosphate in the plasma?

A

HPO4; H2PO-4

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8
Q

True or false?

large changes in the level of phosphate in the extracellular fluid cause major immediate effects on the body

A

false, do not cause

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9
Q

True or false?

slight changes in extracellular calcium can cause extreme immediate physiological effects

A

true

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10
Q

In regards to hypocalcemia causing the nervous system to become more excitable, this is mainly a result of what?

A

increased neuronal membrane permeability to sodium ions

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11
Q

Hypocalcemia may cause seizures. Where is the first sign of this?

A

tetany in the hand causing carpopedal spasm

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12
Q

Tetany ordinarily occurs when the blood concentration of calcium falls form its normal level of ___ mg/dl to about ___ mg/dl

A
  1. 5; 6

note: it is usually lethal at about 4 mg/dl

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13
Q

Usual rates of intake are about ___ mg/day each for calcium and phosphorous

A

1000

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14
Q

Normally, divalent ions are poorly absorbed, but vitamin D promotes calcium absorption by the intestines so that about ___% of ingested calcium is absorbed

A

35

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15
Q

Calcium not absorbed is excreted where?

A

feces

note: about 90% of daily intake is excreted

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16
Q

In regards to renal excretion of calcium and phosphate, __% of the plasma calcium bound to plasma protein is not filtered by glomerular capillaries

A

41

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17
Q

The renal tubules absorb about ___% of the calcium in the filtrate

A

99

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18
Q

PTH can greatly increase __ excretion

A

phosphate

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19
Q

____ crystals fail to precipitate in normal tissues

A

Hydroxyapatite

note: pyrophosphate is an inhibitor

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20
Q

In the initial stage of bone production, osteoblasts secrete ___ monomers which polymerize rapidly to form fibers

A

collagen

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21
Q

The precipitation of calcium along the collagen fibers eventually forms what?

A

hydroxyapatite crystals

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22
Q

If calcium is injected intravaneously it takes ___ to __ minutes for the concentration to return to normal

A

30; 60

note: same for if calcium is removed from body

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23
Q

Exchangeable calcium provides a rapid ___ mechanism

A

buffering

24
Q

what are the 3 hormones that control calcium balance?

A

vitamin D, PTH, calcitonin

25
Q

what is the active form of vitamin D?

A

1,25-dihydroxycholecalciferol

26
Q

What does the active form of vitamin D cause?

A

kidneys and bones to increase absorption of calcium and phosphate into the extracellular fluid

27
Q

The vitamin D receptor forms a complex with another intracellular receptor the _____ receptor, and this complex binds to DNA and activates transription

A

retinoid-X

28
Q

formation of ___ a calcium-binding protein, functions in the brush border of epithelial cells to transport calcium to the cytoplasm

A

calbindin

29
Q

calbindin remains in the cell for how long after the 1,25-dihydroxycholecalciferol has been removed?

A

weeks

30
Q

A calcium stimulated ATPase in the brush border of epithelial cells and an alkaline phosphatase are two ways that 1,25-dihydroxycholecalciferol promotes what?

A

absorption of calcium

31
Q

In the absence of vitamin D, the effect of PTH in causing bone absorption is greatly ____

A

reduced

32
Q

Vitamin D in small quantities ___ bone calcification

A

promotes

note: increases calcium and phosphate absorption from intestines

33
Q

Excess activity of PTH causes what?

A

rapid absorption of calcium salts from bone

note: results in hypercalemia in ECF

34
Q

Synthesis of PTH occurs where?

A

ER and golgi

35
Q

Effects on bone in causing absorption of calcium and phosphate include?

A

a rapid phase that begins in minutes and increases progressively for hours; a much slower phase that results in increased osteoclastic reabsorption of the bone itself

36
Q

true or false?

the cell membranes of both the osteoblasts and the osteoclasts have receptor proteins for binding PTH

A

true

37
Q

The osteoclasts do not have ___ receptor proteins for PTH

A

membrane

38
Q

A major secondary signal used between osteoblasts and osteoclasts is ___ ligand, which activates receptors on preosteoclast cells and transforms them into mature osteoclasts

A

osteoprotegerin

39
Q

What are the two stages of the osteoclastic system?

A

immediate activation of osteoclasts that are already formed, formation of new ones

40
Q

Administration of PTH causes rapid loss of ___ in the urine

A

phosphate

41
Q

PTH increases renal tubular reabsorption of ___ and diminishes reabsorption of ___

A

calcium; phosphate

42
Q

Without the effect of PTH on the kidneys to increase calcium reabsorption, the urine would eventually do what?

A

deplete both ECF and bones of calcium

43
Q

A large share of the effect of PTH on its target organs is mediated by ___

A

cAMP

44
Q

Rickets, pregnancy, and lactation, are all conditions that?

A

decrease calcium ion concentration

45
Q

Calcitonin is secreted by what gland?

A

thyroid

46
Q

Calcitonin tends to decrease plasma ___ concentration

A

calcium

47
Q

Calcitonin is synthesized in and secreted by ___ cells

A

parafollicular (C cells)

48
Q

Any initial reduction of the calcium ion concentration caused by calcitonin leads within hours to a powerful stimulation of ___ secretion

A

PTH

49
Q

In certain bone diseases such as ___ disease, osteoclastic activity is greatly accelerated and calcitonin has a more potent effect on reducing calcium absorption

A

Paget

50
Q

____ occurs when the parathyroid glands do not secrete sufficient PTH

A

hypoparathyroidism

51
Q

What is the usual cause of death from hypoparathyroidism?

A

spasms of laryngeal muscles

52
Q

Primary or secondary hyperthyroidism?

An abnormality of the parathyroid glands causes inappropriate, excess PTH secretions, more prevalent in women.

A

primary

53
Q

Primary or secondary hyperthyroidism?
high levels of PTH occur as a compensation for hypocalcemia, can be caused by vitamin D deficiency which can lead to osteomalacia

A

secondary

54
Q

characteristics of rickets

A

softening and poor mineralization of bones leading to skeletal deformities - severely deficient in vitamin D

55
Q

characteristics of osteoperosis

A

weak bones, loss of bone density - causes fractures

Physiology II (19 decks)

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