Parathyroid, Calcium, Calcitonin And Phosphate

Question 1

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

Answer 1

depression

Question 2

Dec in calcium concentration cause the nervous system to

Bec

Answer 2

be more excited

inc neuronal permeability to sodium ions allowing easy initiation of AP

Question 3

Form most important for most functions of calcium in the body

Answer 3

Ionic form

Question 4

At plasma Ca concentration 50% below normal,

Answer 4

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

Question 5

Hypercalcemia has this effect

Answer 5

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

Question 6

Promotes Ca absorption in intestine

Answer 6

Vitamin D

Question 7

Phosphate is absorbed in the

and excreted in the

Answer 7

intestine

kidney

Question 8

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

Answer 8

PTH

Question 9

organic matrix of the bone

Answer 9

90-95% collagen

10% ground substance

Question 10

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

Answer 10

collagen

Question 11

Ground substance is made up of

Answer 11

Proteoglycan (chondroitin sulfate + hyaluronic acid)

Question 12

Bone salts

Answer 12

calcium
phosphate
Major: hydroxyapatite

Question 13

Collagen fibers provide

Calcium provides

Answer 13

Tensile strength

Compressional strength

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

Question 14

Despite state of supersaturation, hydroxyapatite does not precipitate bec of

Answer 14

pyrophosphate

Question 15

Bone calcification

Answer 15

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.

Question 16

Osteoclast is activated by

Answer 16

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

Question 17

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

Answer 17

Osteoprotegerin

Osteoclastogenesis inhibitory factor OCIF

Question 18

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

Answer 18

Vitamin D

PTH

Question 19

Osteoblasts forms bone by

bone is called

Answer 19

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

Question 20

Canal through which the blood vessels in the bone run is

Answer 20

Haversian canal

Question 21

Stimulates deposition and calcification of bone

Answer 21

Stress

Question 22

Fracture heals by

Answer 22

Formation of callus

Stress on opposite ends of bone accelerate osteoblastic activity

Question 23

Vit D is converted into to inc calcium absorption in intestine

Answer 23

1 25 dihydroxycholecalficerol

Question 24

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

Answer 24

Cholecalciferol Vit D3

Question 25

Cholecalciferol is activated by in the

Answer 25

25 hydroxycholecalciferol liver

Question 26

Feedback inhibitory effect on 25 hydroxy generation is impt bec

Answer 26

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

Question 27

25 hydroxychole is converted to in the requires

Answer 27

1,25 dihydroxycin the proximal tubule Most active PTH

Question 28

Plasma conc of 1,2 is affected inversely by

Answer 28

Calcium in plasma

Question 29

Calcium inversely affects creation of 1,25 bec

Answer 29

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

Question 30

Vitamin D activation happens

Answer 30

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

Question 31

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

Answer 31

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

Question 32

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

Answer 32

calcium reabsorption and preventing secretion

Question 33

Vitamin D causes this effect on bone

Answer 33

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

Question 34

Vitamin D causes bone calcification in amount

Answer 34

smaller amounts

Question 35

PTH is secreted by parathyroid gland cell

Answer 35

Chief cell Oxyphil

Question 36

PTH on calcium and phosphate concentration on. ECF

Answer 36

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

Question 37

PTH effect on kidney

Answer 37

Inc tubular reabs of calcium, mg and hydrogen ion | Inc secretion of phosphate, sodium, potassium and amino acid

Question 38

PTH effect on intestine

Answer 38

Inc calcium and phosphate reabsorption

Question 39

PTH affects target organ by

Answer 39

cAMP | Inc osteocyte osteoclast and target cell

Question 40

Hormone secreted by thyroid to dec calcium concentration Secreted by the cells called which are remnants of

Answer 40

Calcitonin Parafollicular C cells ultimobranchial gland

Question 41

Musce especially sensitive to tetanic spasm in low ca plasma

Answer 41

Laryngeal muscle Causes death