23.3 Calcium Balance

Question 1

What happens if Ca levels rise too high above normal?

Answer 1

1. nervous system becomes progressively damaged.
2. constipation, and sluggish reflexes
3. above 12mg/dl

Question 2

What happens if Ca levels fall too low below normal?

Answer 2

1. nervous sytem become overexcited

Question 3

Where is the majority of Ca stored in teh body?

Answer 3

bones. 1% in the cells/organells. 0.1% in ECF

Question 4

Where is the majority of phosphate stored in the body?

Answer 4

bones. 15% in cells. 1% in ECF

Question 5

Which system is much more tolerant to varying levels of concentration?

Answer 5

phosphate, allows multiple changes without having large effect. Ca has large effect with minor changes

Question 6

What are the effects of hypocalcemia?

Answer 6

1. increased excitability of nervous system

2. seizures, seen in the hand with carpopedal spasm

Question 7

When can tetany become lethal?

Answer 7

at 4mg/dl, onset at

Question 8

how much of Ca intake from diet is absorbed?

Answer 8

only 10%. the rest is excreted. Poor absorption rate in the GI, is improved with Vitamin D

Question 9

What hormone can increase the excretion of phosphate through renal system?

Answer 9

parathyroid hormone. required for survival

Question 10

How much calcium is reabsorbed from the filtrate?

Answer 10

99%, minimal amount is secreted in urine

Question 11

What is present that inhibits the precipitation of hydroxyapatite crytsals, and prevents formation of bone?

Answer 11

pyrophosphate

Question 12

WHat is the benefit of keeping hydroxyapatite in an amorphous (noncrystalline form)?

Answer 12

this allows for faster reabsorption into ECF for migration to different tissues when needed

Question 13

When will calcium salts precipitate to other tissues?

Answer 13

normal conditions, but calcium salt deposition inhibitor factors disappear

Question 14

How rapidly can [Ca] return to normal after large amounts are removed from body fluids?

Answer 14

return to normal in 30 minutes

Question 15

How rapidly can [Ca] return to normla after large amounts are injected IV?

Answer 15

return to normal in 30-60 minutes

Question 16

What is responsible for providing the body the ability to rapidly alter [Ca] levels in circulating fluids?

Answer 16

exchangeable calcium present in all cell types

Question 17

What is the active form of Vitamin D?

Answer 17

1,25-dihydroxycholecalciferol

Question 18

What does the active form of Vitamin D do?

Answer 18

1. increase Ca and phosphate absorption into ECF from the intestine, kidneys, and bones

Question 19

Vit D binds its receptor as what type?

Answer 19

binds as hormone that activates a DNA region

Question 20

What complex does Vit D form in order to activate trasncription?

Answer 20

binds with retinoid X-factor to initiate transcription. is possible to inhibit trasnscirption

Question 21

The absence of Vit D can severely (negatively) affect what other hormone?

Answer 21

PTH, becasue there is reduced calcium transport through cellular membranes.

Question 22

What is the difference of super high Ca presence versus small amount of Ca presence?

Answer 22

1. high amount= absorption into bone

2. low amounts= bone calcification

Question 23

Excess activity of the parathyroid hormone causes what condition?

Answer 23

1. secretion of calcium salts from bones, leading to hypercalcemia

Question 24

Under activity of the parathyroid hormone causes what condition?

Answer 24

1. reduced secretion of calcium salt from bone, leading to hypocalcemia

Question 25

Where is PTH synthesized?

Answer 25

ER and golgi

Question 26

What occurs during the rapid phase of PTH stimulation?

Answer 26

1. results form activation of osteocytes that promote calcium and phosphate absorption
2. begins in minutes and progressively increases for hours

Question 27

WHat occurs during the slow phase of PTH stimulation?

Answer 27

1. over days and weeks

2. osteroclasts proliferate and reabsorb bone

Question 28

How can PTH induce the absorption of Ca and phosphate from bone?

Answer 28

1. PTH binds directly with osteoblasts and osteocytes to activate Ca pumps, causing removal of calcium phosphate salts

Question 29

What effect does PTH have on osteoclasts?

Answer 29

1. no PM PTH receptor
2. two stage activation
   - immediate activation of formed osteoclasts, and stimulate new osteoclast production.
3. causes break down of bone

Question 30

How does PTH affect absorption in the proximal tublar system?

Answer 30

1. phosphate is secreted, not absorbed

2. calcium is rapidly reabsorbed

Question 31

Which ions are reabsorbed with presence of PTH?

Answer 31

1. Mg and H ions

Question 32

Which ions are rapidly secreted with presence of PTH?

Answer 32

1. Na, K, amino acids ions are highly secreted

Question 33

What would happen if the parathyroid were surgically removed?

Answer 33

1. loss of PTH

2. urine would deplete ECF and calcium of the bones

Question 34

What conditions/diseases will contribute to decreased ca ion concentration?

Answer 34

1. rickets
2. pregnancy
3. lactation

Question 35

What conditions can increase Ca ions above the normal value range?

Answer 35

1. excessive Ca intake
2. increased Vit D
3. Bone absorption secondary to disease

Question 36

How are decreased ca ion levels detected and corrected?

Answer 36

1. low Ca ion detected by parathyroid. which releases PTH
2. PTH acts to increase bone resoprtion;releasing Ca
3. PTH acts on kidneys to secrete phosphate, absorb Ca, and vitamin D to help with absorption of Ca in the intestine

Question 37

What organs can help increase Ca levels int he body?

Answer 37

bone, kidneys, and intestine

Question 38

Where is calcitonin secreted from?

Answer 38

1. thyroid gland

Question 39

What is the common effect of calcitonin?

Answer 39

1. decrease plasma calcium concentration

Question 40

Were is calcitonin formed?

Answer 40

1. parafollicular cells

Question 41

Does calcitonin have a strong or weak effect on Ca ion concentration in the human body?

Answer 41

weak effect, that ‘s followed by powerful effect of PTH

Question 42

In what specific case can calcitonin have a strong effec int reducing calcium reabsorption?

Answer 42

paget’s disease, wher osteoclast activity is severely high

Question 43

What happens in hypoparathyroidism?

Answer 43

1. reduced PTH, inactivates osteoclasts
2. this reduces blood Ca levels
3. this can lead to tetany. start with laryngeal muscles

Question 44

What is primary hyperparathyroidism?

Answer 44

1. abnormality of parathyroid glands secrete excess PTH

2. prevalent in women bc of lactation and pregnancy

Question 45

What is secondary hyperparathyroidism?

Answer 45

1. high PTH levels to compensate for hypocalcemia

2. Vit D deficiency leading to osteomalacia