Calcium Balance (Lec 18)

Question 1

Increases in calcium ions above normal cause progressive depression of what?

Answer 1

nervous system

Question 2

symptoms of hypercalemia tend to appear when the blood calcium level rises above ___ mg/dl

Answer 2

12

Question 3

Decreases in calcium storage cause the nervous system to become more ___

Answer 3

excited

Question 4

___ % of the total body calcium is in the extracellular fluid

Answer 4

0.1

Question 5

___ % of the calcium in the body is in the cells and organelles, the rest is stored in ___

Answer 5

1; bones

Question 6

Breakdown the store of phosphate in bones, cells and ECF

Answer 6

bones: 85 %
cells: 14-15%
ECF: less than 1%

Question 7

What are the two forms of inorganic phosphate in the plasma?

Answer 7

HPO4; H2PO-4

Question 8

True or false?

large changes in the level of phosphate in the extracellular fluid cause major immediate effects on the body

Answer 8

false, do not cause

Question 9

True or false?

slight changes in extracellular calcium can cause extreme immediate physiological effects

Answer 9

true

Question 10

In regards to hypocalcemia causing the nervous system to become more excitable, this is mainly a result of what?

Answer 10

increased neuronal membrane permeability to sodium ions

Question 11

Hypocalcemia may cause seizures. Where is the first sign of this?

Answer 11

tetany in the hand causing carpopedal spasm

Question 12

Tetany ordinarily occurs when the blood concentration of calcium falls form its normal level of ___ mg/dl to about ___ mg/dl

Answer 12

9. 5; 6

note: it is usually lethal at about 4 mg/dl

Question 13

Usual rates of intake are about ___ mg/day each for calcium and phosphorous

Answer 13

1000

Question 14

Normally, divalent ions are poorly absorbed, but vitamin D promotes calcium absorption by the intestines so that about ___% of ingested calcium is absorbed

Answer 14

35

Question 15

Calcium not absorbed is excreted where?

Answer 15

feces

note: about 90% of daily intake is excreted

Question 16

In regards to renal excretion of calcium and phosphate, __% of the plasma calcium bound to plasma protein is not filtered by glomerular capillaries

Answer 16

41

Question 17

The renal tubules absorb about ___% of the calcium in the filtrate

Answer 17

99

Question 18

PTH can greatly increase __ excretion

Answer 18

phosphate

Question 19

____ crystals fail to precipitate in normal tissues

Answer 19

Hydroxyapatite

note: pyrophosphate is an inhibitor

Question 20

In the initial stage of bone production, osteoblasts secrete ___ monomers which polymerize rapidly to form fibers

Answer 20

collagen

Question 21

The precipitation of calcium along the collagen fibers eventually forms what?

Answer 21

hydroxyapatite crystals

Question 22

If calcium is injected intravaneously it takes ___ to __ minutes for the concentration to return to normal

Answer 22

30; 60

note: same for if calcium is removed from body

Question 23

Exchangeable calcium provides a rapid ___ mechanism

Answer 23

buffering

Question 24

what are the 3 hormones that control calcium balance?

Answer 24

vitamin D, PTH, calcitonin

Question 25

what is the active form of vitamin D?

Answer 25

1,25-dihydroxycholecalciferol

Question 26

What does the active form of vitamin D cause?

Answer 26

kidneys and bones to increase absorption of calcium and phosphate into the extracellular fluid

Question 27

The vitamin D receptor forms a complex with another intracellular receptor the _____ receptor, and this complex binds to DNA and activates transription

Answer 27

retinoid-X

Question 28

formation of ___ a calcium-binding protein, functions in the brush border of epithelial cells to transport calcium to the cytoplasm

Answer 28

calbindin

Question 29

calbindin remains in the cell for how long after the 1,25-dihydroxycholecalciferol has been removed?

Answer 29

weeks

Question 30

A calcium stimulated ATPase in the brush border of epithelial cells and an alkaline phosphatase are two ways that 1,25-dihydroxycholecalciferol promotes what?

Answer 30

absorption of calcium

Question 31

In the absence of vitamin D, the effect of PTH in causing bone absorption is greatly ____

Answer 31

reduced

Question 32

Vitamin D in small quantities ___ bone calcification

Answer 32

promotes note: increases calcium and phosphate absorption from intestines

Question 33

Excess activity of PTH causes what?

Answer 33

rapid absorption of calcium salts from bone note: results in hypercalemia in ECF

Question 34

Synthesis of PTH occurs where?

Answer 34

ER and golgi

Question 35

Effects on bone in causing absorption of calcium and phosphate include?

Answer 35

a rapid phase that begins in minutes and increases progressively for hours; a much slower phase that results in increased osteoclastic reabsorption of the bone itself

Question 36

true or false? | the cell membranes of both the osteoblasts and the osteoclasts have receptor proteins for binding PTH

Answer 36

true

Question 37

The osteoclasts do not have ___ receptor proteins for PTH

Answer 37

membrane

Question 38

A major secondary signal used between osteoblasts and osteoclasts is ___ ligand, which activates receptors on preosteoclast cells and transforms them into mature osteoclasts

Answer 38

osteoprotegerin

Question 39

What are the two stages of the osteoclastic system?

Answer 39

immediate activation of osteoclasts that are already formed, formation of new ones

Question 40

Administration of PTH causes rapid loss of ___ in the urine

Answer 40

phosphate

Question 41

PTH increases renal tubular reabsorption of ___ and diminishes reabsorption of ___

Answer 41

calcium; phosphate

Question 42

Without the effect of PTH on the kidneys to increase calcium reabsorption, the urine would eventually do what?

Answer 42

deplete both ECF and bones of calcium

Question 43

A large share of the effect of PTH on its target organs is mediated by ___

Answer 43

cAMP

Question 44

Rickets, pregnancy, and lactation, are all conditions that?

Answer 44

decrease calcium ion concentration

Question 45

Calcitonin is secreted by what gland?

Answer 45

thyroid

Question 46

Calcitonin tends to decrease plasma ___ concentration

Answer 46

calcium

Question 47

Calcitonin is synthesized in and secreted by ___ cells

Answer 47

parafollicular (C cells)

Question 48

Any initial reduction of the calcium ion concentration caused by calcitonin leads within hours to a powerful stimulation of ___ secretion

Answer 48

PTH

Question 49

In certain bone diseases such as ___ disease, osteoclastic activity is greatly accelerated and calcitonin has a more potent effect on reducing calcium absorption

Answer 49

Paget

Question 50

____ occurs when the parathyroid glands do not secrete sufficient PTH

Answer 50

hypoparathyroidism

Question 51

What is the usual cause of death from hypoparathyroidism?

Answer 51

spasms of laryngeal muscles

Question 52

Primary or secondary hyperthyroidism? | An abnormality of the parathyroid glands causes inappropriate, excess PTH secretions, more prevalent in women.

Answer 52

primary

Question 53

Primary or secondary hyperthyroidism? high levels of PTH occur as a compensation for hypocalcemia, can be caused by vitamin D deficiency which can lead to osteomalacia

Answer 53

secondary

Question 54

characteristics of rickets

Answer 54

softening and poor mineralization of bones leading to skeletal deformities - severely deficient in vitamin D

Question 55

characteristics of osteoperosis

Answer 55

weak bones, loss of bone density - causes fractures