Exam 3: Calcium Balance Flashcards
Increases in _____ cause progressive depression of the nervous system.
Calcium
Decreases in _____ cause the nervous system to become more excited.
Calcium
What percentage of calcium is in the extracellular fluid?
0.1%
What percentage of calcium is in the cells and organelles?
1%
What percentage of calcium is in the bones?
~99%
85% of _____ is stored in bones.
Phosphate
T/F: Hypocalcemia causes nervous system excitement and tetany & seizures.
True
Tetany occurs when calcium falls from normal level of _____ to about _____.
9.5 mg/dl
6 mg/dl
_____ promotes calcium absorption by the intestines so that about _____ of ingested calcium is absorbed.
Vitamin D
35%
What percentage of daily intake of calcium is excreted?
~90%
About how much of the ingested calcium is excreted in the urine daily?
100 mg/day
_____ can greatly increase phosphate excretion
PTH
What is an inhibitor of hydroxyapatite?
Pyrophosphate
T/F: Bone may secrete a pyrophosphate inhibitor to allow hydroxyapatite precipitation.
True
The precipitation of calcium along the collagen fibers forms _____ _____.
Hydroxyapatite crystals
What form does some calcium salt remain in to be rapidly absorbed when needed in the extracellular fluid?
Amorphous form
T/F: Calcium concentrations return to normal within 12 hours of removal or addition of intravenous calcium.
False, within 30 minutes
What 3 hormones control calcium balance?
Vitamin D
PTH
Calcitonin
What causes intestines, kidneys, & bones to increase absorption of calcium and phosphate?
Vitamin D
Where are vitamin D receptors mainly located?
Nuclei of target cells
Calbindin (in intestinal epithelial cells) functions to…?
Transport calcium into the cell cytoplasm
T/F: Vitamin D always promotes bone calcification.
False, only in smaller quantities
Excess _____ causes rapid absorption of calcium salts from the bones.
PTH
Excess of _____ results in hypercalcemia.
PTH
Which phase of PTH results from activation of already existing bone cells to promote calcium and phosphate absorption?
Rapid phase
Which phase of PTH results from proliferation of the osteoclasts & reabsorption of bone itself, not merely absorption of the calcium phosphate salts?
Slower phase
T/F: Osteoclasts have membrane receptor proteins for PTH.
False, do not
Administration of _____ causes rapid loss of phosphate in the urine & increases renal tubular reabsorption of calcium.
PTH
What would cause the urine to eventually deplete the extracellular fluid & bones of calcium?
Loss of PTH activity of kidneys
Rickets, pregnancy, & lactation are conditions that do what?
Decrease calcium ion concentration
Excess calcium in diet, increased vitamin D, & bone absorption by disease are conditions that do what?
Increase calcium ion concentration
Calcitonin is secreted by what?
Thyroid gland
Calcitonin tends to _____ plasma calcium concentration.
Decrease
What is synthesized and secreted by parafollicular cells?
Calcitonin
When parathyroid glands are removed, calcium level in the blood _____ & blood phosphate concentration may _____.
Falls
Double
What is an abnormality of the parathyroid glands that affects the actual gland?
Primary hyperparathyroidism
What is a compensation for hypocalcemia caused by vitamin D deficiency leading to osteomalacia?
Secondary hyperparathyroidism
What is usually in children and results from calcium or phosphate deficiency in the extracellular fluid, caused by a lack of vitamin D?
Rickets
What is caused by lack of physical stress on the bones, malnutrition, lack of vitamin C, old age, Cushing’s, and lack of estrogn?
Osteopororsis
T/F: Osteoporosis is due to diminished osteoblastic activity and diminished organic bone martix.
True
