Exam 3: Calcium Balance

Question 1

Increases in _____ cause progressive depression of the nervous system.

Answer 1

Calcium

Question 2

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

Answer 2

Calcium

Question 3

What percentage of calcium is in the extracellular fluid?

Answer 3

0.1%

Question 4

What percentage of calcium is in the cells and organelles?

Answer 4

1%

Question 5

What percentage of calcium is in the bones?

Answer 5

~99%

Question 6

85% of _____ is stored in bones.

Answer 6

Phosphate

Question 7

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

Answer 7

True

Question 8

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

Answer 8

9.5 mg/dl

6 mg/dl

Question 9

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

Answer 9

Vitamin D

35%

Question 10

What percentage of daily intake of calcium is excreted?

Answer 10

~90%

Question 11

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

Answer 11

100 mg/day

Question 12

_____ can greatly increase phosphate excretion

Answer 12

PTH

Question 13

What is an inhibitor of hydroxyapatite?

Answer 13

Pyrophosphate

Question 14

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

Answer 14

True

Question 15

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

Answer 15

Hydroxyapatite crystals

Question 16

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

Answer 16

Amorphous form

Question 17

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

Answer 17

False, within 30 minutes

Question 18

What 3 hormones control calcium balance?

Answer 18

Vitamin D
PTH
Calcitonin

Question 19

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

Answer 19

Vitamin D

Question 20

Where are vitamin D receptors mainly located?

Answer 20

Nuclei of target cells

Question 21

Calbindin (in intestinal epithelial cells) functions to…?

Answer 21

Transport calcium into the cell cytoplasm

Question 22

T/F: Vitamin D always promotes bone calcification.

Answer 22

False, only in smaller quantities

Question 23

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

Answer 23

PTH

Question 24

Excess of _____ results in hypercalcemia.

Answer 24

PTH

Question 25

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

Answer 25

Rapid phase

Question 26

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

Answer 26

Slower phase

Question 27

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

Answer 27

False, do not

Question 28

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

Answer 28

PTH

Question 29

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

Answer 29

Loss of PTH activity of kidneys

Question 30

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

Answer 30

Decrease calcium ion concentration

Question 31

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

Answer 31

Increase calcium ion concentration

Question 32

Calcitonin is secreted by what?

Answer 32

Thyroid gland

Question 33

Calcitonin tends to _____ plasma calcium concentration.

Answer 33

Decrease

Question 34

What is synthesized and secreted by parafollicular cells?

Answer 34

Calcitonin

Question 35

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

Answer 35

Falls | Double

Question 36

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

Answer 36

Primary hyperparathyroidism

Question 37

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

Answer 37

Secondary hyperparathyroidism

Question 38

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

Answer 38

Rickets

Question 39

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

Answer 39

Osteopororsis

Question 40

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

Answer 40

True