Calcium Regulation

Question 1

Total plasma ca

Answer 1

0.9-2.5mM

Reversibly binds to albumen so diffusable conc of pro bound is 0.9 and 1.6 is ultrafilterable

Question 2

Breakdown of ultrafilterable ca

Answer 2

0. 3 firmly bound to citrate or phosphate

1. 3 ionic ca : 0.8 is ionised but inact so only 0.5 is act ca

Question 3

Ca sources

Answer 3

IC - mitoch and er
Blood and ecf - 40-50% in blood is bound to pro
Bine ca - 99% in mineral phasr
1% in pool for rapid exchange with ec ca

Question 4

EC ca sensing recs

Answer 4

Gpro couples rec
Expressed on range of cells incl para and thyr, bones kis GI mucosa
Act with 2 major signal transducing effects

Question 5

Ca sensing rec signal transducng effects

Answer 5

Phospholipase C act lead to 2nd messenger generation

Adenylatr cyclase inhib cause suppress IC cAMP

Question 6

Organ regulation of ca

Answer 6

Bone - vast reservoir
Kid critically important in homeostasis. Most ca filtered is reabs
SI abs ca dep on expression of ca bind pro in epi cells

Question 7

PTH prod and cell types in PT gland

Answer 7

By PT gland
Chief cells secr PTH in resp to low ca - no distinguishing features
Oxyphillic cells - in human ox and horse - large with many mitoch
Adipocytes

Question 8

PTG release

Answer 8

Chief cells exocyt granules cont PTH

Lower ca cause faster PTh release and sens to rate of active ca fall

Question 9

PTH tissue sens

Answer 9

Tissue sensitivity to PTH varied

SI and kid more sens than osteoclasts

Question 10

PTH rec

Answer 10

T1 most abundant in bone and kid

T2 expressed in few tissues

Question 11

PTH affects on bone

Answer 11

Inhib osteoblast ca deposition (rec on resting OB) low level stim OB multipl and bone depos, high level pass on message from OB via paracr secr that stim osteocytes to incr plasma ca by incr ca removal from bone mineral and release jnto ecf. Also slowly stim OC to resorp bone mateix and release ca and p into plasma

Question 12

PTH effect kid

Answer 12

Suppr ca loss
Incr ca reabs by dct
Inhib p reabs and stim p loss in pct
Stim 1a hydroxylase to gen calcitriol

Question 13

PTH effect SI

Answer 13

Incr ca abs

Indirect as stim vit d prod in kid to induce ca bind pro synth in intest epi cells

Question 14

Calcitonin prod

Answer 14

Parafollocular cells of thyr

Large clear cells migrated to thyr from neural crest

Question 15

Calcitonin fx

Answer 15

Decr ca level
Signif in fish rodents and some domestic species
Emergency mech for high ca
Most key in young

Question 16

Calcitonin effect on kid

Answer 16

Suppr ca reavs and p

Enhance excr

Question 17

Calcitonin effect on bone

Answer 17

Inhib bone resorp and min ca fluxes
Stim OB to form bone and take ca from curc
Inhib OC tonprev ca and p mobilisation

Question 18

Calcitriol fx

Answer 18

Incr blood ca
Facilitate SI abs and enhance ca fluxes out of bone with PTH
6hr half life

Question 19

Calcitriol/vit d synth

Answer 19

Liver - hepatic synth of 25 hydroxycholecalciferol - loosely reg blood levels reflext vit d prod in skin and ingested
Kid - 1a hydroxylase act in kid is tightly reg and major control pt

Question 20

Stim 1a hydroxylase

Answer 20

Pth
Hypocalcae
Hypophosphat

Question 21

Vit d rec

Answer 21

Present in most or all body cells
Pitent effect on g and differentiation of many crlls
Broad effects
IC rec induce spec pro synth

Question 22

Vit d effects on bone

Answer 22

Prov proper ca:p ratio to support mineralisatio
Act on OB and indirectly stim OC
Transcriptional regulator of bone matrix pro - induce osteocalcin expression and red T1 coll synth

Question 23

Vir d effect on si

Answer 23

Big effect on ca uptake by intest cells as direct action on brush border

Question 24

Vir d effect on kid

Answer 24

Weak incr of ca abs by renal tub

Question 25

Hyperparat 1o

Answer 25

Extensive bone loss as incr PTH Hypercal Incr ca loss in urine as filtered load more than resorp capacity Chronic hypercal cause abd pain nausea vom constipation decr appetite kid stone bone fract sudden heart attacke

Question 26

Hyperparat 2o

Answer 26

Kid dis cause excess PTH secr due to chronic ren failure as decr ca level cause incr PTH cause hyper cal Inadeq nutrition vit d or ca some lung tumours and decalcification of bones (rubber bone) also cause

Question 27

Hypoparat

Answer 27

Inadeq PTH rare Removed pt glabd cause decr ca and decr synaptic transmission Hyperexcitability of nn and mm

Question 28

Hypocal

Answer 28

M fatigue tetany convulsions cardiac arrhythmia abd pain m cramp Treat by restoring normal ca by infusion supplement or vit d therapy

Question 29

Calcitriol def

Answer 29

Rickets Lack vit d or ca cause decr ca abs so inadeq calcification of bones High PTH as low ca Can be 2o to ren dis

Question 30

Sun - vit d

Answer 30

Horse human rat ox sheep pig have enough 7 dehydrocholesterol to convert to cholecalciferol. Dog and cat have little/none

Question 31

Vit d toxicity

Answer 31

Only by dietary not by sun exposure