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Physiology > Parathyroid, Calcium, Calcitonin And Phosphate > Flashcards

Parathyroid, Calcium, Calcitonin And Phosphate Flashcards

1
Q

Inc in calcium ion concentration above normal cause this effect on CNS

A

depression

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2
Q

Dec in calcium concentration cause the nervous system to

Bec

A

be more excited

inc neuronal permeability to sodium ions allowing easy initiation of AP

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3
Q

Form most important for most functions of calcium in the body

A

Ionic form

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4
Q

At plasma Ca concentration 50% below normal,

A

Peripheral nerves become excitable they begin to discharge spontaneously initiating trains of nerve impulses that pass to peripheral skeletal ms
Tetany
Seizures

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5
Q

Hypercalcemia has this effect

A 
Depressed
Sluggish reflex
Dec QT interval 
Lack of appetite
Constipation (dep contractility of GI muscle)
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6
Q

Promotes Ca absorption in intestine

A

Vitamin D

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7
Q

Phosphate is absorbed in the

and excreted in the

A

intestine

kidney

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8
Q

Most important factor controlling reabsorption of Ca in distal portion of nephron and the rate of excretion is

A

PTH

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9
Q

organic matrix of the bone

A

90-95% collagen

10% ground substance

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10
Q

extend primarily along lines of tensional forces and give bone its tensile strength

A

collagen

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11
Q

Ground substance is made up of

A

Proteoglycan (chondroitin sulfate + hyaluronic acid)

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12
Q

Bone salts

A

calcium
phosphate
Major: hydroxyapatite

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13
Q

Collagen fibers provide

Calcium provides

A

Tensile strength

Compressional strength

Collagen fiber lying adjacent to hydroxyapatite and overlap arrangement provide strength to bone

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14
Q

Despite state of supersaturation, hydroxyapatite does not precipitate bec of

A

pyrophosphate

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15
Q

Bone calcification

A

Osteoblast producr collagen molecules + ground substance
Collagen monomers polymerize rapidly to form collagen fibers becoming osteoid where calcium salts readily precipitate
Osteoblasts trapped in osteoids becoming osteocytes
Calcium precipitation on collagen surface forming minute nidi growing into hydroxyapatite
Osteoblast secrete inhibitor to pyrophosphate preventing crystalization.

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16
Q

Osteoclast is activated by

A

PTH binding to receptors of adjacent osteoblast causing them to release osteoprotegrin ligand, a cytokine also known as RANKL

OPGL activates receptors on prosteoclast cells causing them to differentiate into mature multinucleated osteoclasts

Mature osteoclasts develop ruffled border and release enzyme that promote bone resorption

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17
Q

This cytokine produced by osteoblasts inhibit bone resportion acting as decoy receptor binding to OPGL inhibiting diff of preosteoclast into mature osteoclast that resorb bone

A

Osteoprotegerin

Osteoclastogenesis inhibitory factor OCIF

18
Q

Stimulate production of OPGL through inhibition of OPG and stimulating OPGL formation

A

Vitamin D

PTH

19
Q

Osteoblasts forms bone by

bone is called

A

Bone being laid down in successive layers of concentric circles (lamellae) on inner surface of cavity until tunnel is filled
Deposition stops when bone encroaches blood vessels supplying area

osteon

20
Q

Canal through which the blood vessels in the bone run is

A

Haversian canal

21
Q

Stimulates deposition and calcification of bone

A

Stress

22
Q

Fracture heals by

A

Formation of callus

Stress on opposite ends of bone accelerate osteoblastic activity

23
Q

Vit D is converted into to inc calcium absorption in intestine

A

1 25 dihydroxycholecalficerol

24
Q

Formed in the skin as a result of irradiation of 7 dehydrocholesterol by UV, most important compoung from sterol

A

Cholecalciferol Vit D3

25
Q

Cholecalciferol is activated by

in the

A

25 hydroxycholecalciferol

liver

26
Q

Feedback inhibitory effect on 25 hydroxy generation is impt bec

A

1 regulates the concentration of 25 hydroxy in plasma despite inc intake of D3
2 high degree of feedback prevents excessive action of Vit D When D3 intake is altered and conserves Vit D stores in liver

27
Q

25 hydroxychole is converted to

in the

requires

A

1,25 dihydroxycin the proximal tubule
Most active

PTH

28
Q

Plasma conc of 1,2 is affected inversely by

A

Calcium in plasma

29
Q

Calcium inversely affects creation of 1,25 bec

A

1 it has slight effect in preventing conversion of 25 hydroxy to 1,25
2 rate of secretion of PTH is greatly supressed when plasma calcium ion rises above 9-10 hence lower conversion of 25 to 1,25
a high calcium conc 25 is converted to 24,25 dihydroxycholecalciferol

30
Q

Vitamin D activation happens

A

By binding with receptor at DNA
forming complex with another intracellular receptor retinoid X receptor
complex binding to DNA ane activating transcription

31
Q

1,25 dihydroxy is a hormone that promotes calcium with phosphate absorption in intestine by formation of

A

calbindin
a calcium binding protein in the brushborder to transport calcium in cell cytoplasm

Rate of calcium absorption is directly proportional to quantity of calcium binding protein remains despite elimination of 1,25

Also forms calcium stimulated ATPase in brush border of epithelial cell and ALP in eithelial cell

32
Q

1,25 also promotes calcium and phosphate in serum by acting on renal tubule

A

calcium reabsorption and preventing secretion

33
Q

Vitamin D causes this effect on bone

A

absorption

Absence of Vit D Inhibits effect of PTH on in bone absorption

34
Q

Vitamin D causes bone calcification in amount

A

smaller amounts

35
Q

PTH is secreted by

parathyroid gland cell

A

Chief cell

Oxyphil

36
Q

PTH on calcium and phosphate concentration on. ECF

A

inc calcium and phosphate absorption from bone
rapid effect of PTH to dec excretion of calcium by kidneys
Decline in phosphate due to inc renal phosphate excretion

37
Q

PTH effect on kidney

A

Inc tubular reabs of calcium, mg and hydrogen ion

Inc secretion of phosphate, sodium, potassium and amino acid

38
Q

PTH effect on intestine

A

Inc calcium and phosphate reabsorption

39
Q

PTH affects target organ by

A

cAMP

Inc osteocyte osteoclast and target cell

40
Q

Hormone secreted by thyroid to dec calcium concentration

Secreted by the cells called

which are remnants of

A

Calcitonin

Parafollicular C cells

ultimobranchial gland

41
Q

Musce especially sensitive to tetanic spasm in low ca plasma

A

Laryngeal muscle

Causes death

Physiology (23 decks)

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