Exam 3: Calcium Balance Flashcards

1
Q

Increases in _____ cause progressive depression of the nervous system.

A

Calcium

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2
Q

Decreases in _____ cause the nervous system to become more excited.

A

Calcium

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3
Q

What percentage of calcium is in the extracellular fluid?

A

0.1%

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4
Q

What percentage of calcium is in the cells and organelles?

A

1%

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5
Q

What percentage of calcium is in the bones?

A

~99%

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6
Q

85% of _____ is stored in bones.

A

Phosphate

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7
Q

T/F: Hypocalcemia causes nervous system excitement and tetany & seizures.

A

True

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8
Q

Tetany occurs when calcium falls from normal level of _____ to about _____.

A

9.5 mg/dl

6 mg/dl

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9
Q

_____ promotes calcium absorption by the intestines so that about _____ of ingested calcium is absorbed.

A

Vitamin D

35%

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10
Q

What percentage of daily intake of calcium is excreted?

A

~90%

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11
Q

About how much of the ingested calcium is excreted in the urine daily?

A

100 mg/day

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12
Q

_____ can greatly increase phosphate excretion

A

PTH

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13
Q

What is an inhibitor of hydroxyapatite?

A

Pyrophosphate

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14
Q

T/F: Bone may secrete a pyrophosphate inhibitor to allow hydroxyapatite precipitation.

A

True

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15
Q

The precipitation of calcium along the collagen fibers forms _____ _____.

A

Hydroxyapatite crystals

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16
Q

What form does some calcium salt remain in to be rapidly absorbed when needed in the extracellular fluid?

A

Amorphous form

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17
Q

T/F: Calcium concentrations return to normal within 12 hours of removal or addition of intravenous calcium.

A

False, within 30 minutes

18
Q

What 3 hormones control calcium balance?

A

Vitamin D
PTH
Calcitonin

19
Q

What causes intestines, kidneys, & bones to increase absorption of calcium and phosphate?

A

Vitamin D

20
Q

Where are vitamin D receptors mainly located?

A

Nuclei of target cells

21
Q

Calbindin (in intestinal epithelial cells) functions to…?

A

Transport calcium into the cell cytoplasm

22
Q

T/F: Vitamin D always promotes bone calcification.

A

False, only in smaller quantities

23
Q

Excess _____ causes rapid absorption of calcium salts from the bones.

A

PTH

24
Q

Excess of _____ results in hypercalcemia.

A

PTH

25
Q

Which phase of PTH results from activation of already existing bone cells to promote calcium and phosphate absorption?

A

Rapid phase

26
Q

Which phase of PTH results from proliferation of the osteoclasts & reabsorption of bone itself, not merely absorption of the calcium phosphate salts?

A

Slower phase

27
Q

T/F: Osteoclasts have membrane receptor proteins for PTH.

A

False, do not

28
Q

Administration of _____ causes rapid loss of phosphate in the urine & increases renal tubular reabsorption of calcium.

A

PTH

29
Q

What would cause the urine to eventually deplete the extracellular fluid & bones of calcium?

A

Loss of PTH activity of kidneys

30
Q

Rickets, pregnancy, & lactation are conditions that do what?

A

Decrease calcium ion concentration

31
Q

Excess calcium in diet, increased vitamin D, & bone absorption by disease are conditions that do what?

A

Increase calcium ion concentration

32
Q

Calcitonin is secreted by what?

A

Thyroid gland

33
Q

Calcitonin tends to _____ plasma calcium concentration.

A

Decrease

34
Q

What is synthesized and secreted by parafollicular cells?

A

Calcitonin

35
Q

When parathyroid glands are removed, calcium level in the blood _____ & blood phosphate concentration may _____.

A

Falls

Double

36
Q

What is an abnormality of the parathyroid glands that affects the actual gland?

A

Primary hyperparathyroidism

37
Q

What is a compensation for hypocalcemia caused by vitamin D deficiency leading to osteomalacia?

A

Secondary hyperparathyroidism

38
Q

What is usually in children and results from calcium or phosphate deficiency in the extracellular fluid, caused by a lack of vitamin D?

A

Rickets

39
Q

What is caused by lack of physical stress on the bones, malnutrition, lack of vitamin C, old age, Cushing’s, and lack of estrogn?

A

Osteopororsis

40
Q

T/F: Osteoporosis is due to diminished osteoblastic activity and diminished organic bone martix.

A

True