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COB Physiology II > Lecture 23: Calcium Balance > Flashcards

Lecture 23: Calcium Balance Flashcards

1
Q

What are the effects of hypercalcemia?

A

Depression of nervous system, reflexes sluggish, constipation and lack of appetite

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2
Q

List the distribution of calcium in the ECF, cells, and bones.

A

ECF contains 0.1% of Ca2+ in body; Cells contain 1% of body’s calcium. The rest is stored in bones

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3
Q

List the distribution of phosphate storage in the ECF, cells, and bones.

A

Less than 1% phosphate in ECF; 14% in cells. 85% phosphate stored in bones

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4
Q

Compare the effect of large changes in phosphate levels in the ECF vs. large changes of calcium levels in the ECF.

A

Large changes in phosphate levels do not cause major immediate effects on the body; Even slight changes in extracellular calcium cause extreme changes

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5
Q

What are the effects of hypocalcemia?

A

Excitement of nervous system, tetany, possibly death

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6
Q

Hypocalcemia is lethal when Calcium concentration is at what level in the body?

A. 4 mg/dl
B. 6 mg/dl
C. 9.5 mg/dl
D. 12 mg/dl

A

A. 4 mg/dl

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7
Q

Usual rate of calcium intake is ~1000 mg/day. How much of this calcium is excreted?

A. 1000 mg
B. 100 mg
C. 990 mg
D. 900 mg

A

D. 900 mg

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8
Q

What hormone greatly increases the rate of phosphate excretion?

A

PTH

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9
Q

Why do hydroxyapatite crystals fail to precipitate in normal tissues (except bone)?

A

Inhibitors such as pyrophosphate are present in tissues and plasma to prevent precipitation

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10
Q

What is the purpose of exchangeable calcium in the body?

A

Provides a buffering mechanism to keep calcium levels in equilibrium and maintain calcium concentration in a narrow range

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11
Q

What are the 3 hormones that control calcium balance?

A

Vitamin D, PTH, Calcitonin

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12
Q

What is the active form of vitamin D?

A

1, 25-dihydroxycholecalciferol

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13
Q

Where are most vitamin D receptors found?

A

Present in most cells of the body; located mainly in nuclei of target cells

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14
Q

Which of the following promotes intestinal absorption of calcium over a period of two days?

A. 1,25-dihydroxycholecalciferol
B. calcitonin
C. calbindin
D. vitamin D

A

C. calbindin

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15
Q

What are the effects of administering extreme quantities of vitamin D?

A

Absorption of bone

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16
Q

What are the effects of administering smaller quantities of vitamin D?

A

Bone calcification by increasing absorption of calcium and phosphate from intestines

17
Q

What are the results of excessive activity of the parathyroid glands?

A

Hypercalcemia in ECF due to rapid absorption of calcium salts from bones

18
Q

What are the results of hypofunction of the parathyroid glands?

A

Hypocalcemia, tetany

19
Q

What is the effect of PTH on the kidneys?

A. increase reabsorption of sodium
B. increase reabsorption of phosphate
C. increase reabsorption of calcium
D. increase reabsorption of sodium, phosphate, and calcium

A

C. increase in absorption of calcium

20
Q

How does PTH affect osteoclasts?

A

Binds to osteoprotegerin ligand that activates receptors on preosteoclast cells and transforms them into mature osteoclasts

21
Q

What conditions increase calcium ion concentration above normal?

A

Excess quantities of calcium or vitamin D in the diet, bone absorption caused by disease

22
Q

How is calcitonin secreted and what is its function?

A

Secreted by C (parafollicular cells) of the thyroid gland; decreases plasma calcium concentration

23
Q

What are the results of hypoparathyroidism?

A

Osteoclasts become almost totally inactive, calcium vevels decrease; tetany and death may occur

24
Q

What is the cause of primary hyperparathyroidism?

A

Abnormality (like a tumor) of the parathyroid glands causes excess PTH secretions - more common in women

25
Q

What is the cause of secondary hyperparathyroidism?

A

High levels of PTH occur to compensate for hypocalcemia - may be caused by vitamin D deficiency

26
Q

What are the causes and characteristics of Rickets?

A

Caused by vitamin D deficiency in children; decreased concentration of calcium, weak bones, tetany

27
Q

What are the causes and characteristics of Osteoporosis?

A

Caused by inactivity, malnutrition, lack of vitamin C, lack of estrogen in females, aging, Cushing’s; weak bones

COB Physiology II (18 decks)

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