Calcium homeostasis

Question 1

when calcium is ionised it is inactive/active ?
when calcium is protein bound it is inactive/active ?

Answer 1

active
inactive

Question 2

what is calcium bound to in bone

Answer 2

phosphates

Question 3

what are the 3 hormones involved in calcium homeostasis

Answer 3

1,25-dihydroxyvitamin D
parathyroid hormone
calcitonin

Question 4

where is parathyroid hormone produced

Answer 4

chief cells of parathyroid gland

Question 5

parathyroid hormone responds to hyper/hypocalcaemia?

Answer 5

hypocalcaemia

Question 6

what the pathway that involves the CaSR

Answer 6

calcium binds to CaSR activating PLC
PLC converts PIP2 into DAG + IP3
IP3 triggers release of Ca from SR/ER

Question 7

what type of receptors are located on osteoblasts

Answer 7

PTH receptors

Question 8

what is PTH responsible for

Answer 8

increasing extracellular Ca

Question 9

how does PTH work on bone

Answer 9

stimulates cytokines that recruit osteoblasts that then induce osteoclasts

Question 10

why are osteoclasts important in terms of Ca

Answer 10

help break down hydroxyapitie crystals

Question 11

effect of PTH on small instestine

Answer 11

activates synthesis of 1,25-dihydroxyviamin D

Question 12

effect of PTH on kidneys

Answer 12

increases Ca reabsorption by increasing activity of Ca pumps and channels
and increases phosphate excretion

Question 13

where is 1,25-dihydroxyvitamin D (calcitriol) produced

Answer 13

kidneys

Question 14

why are osteoclasts good for increasing Ca conc in blood

Answer 14

they break down bone to release phosphate and Ca into blood

Question 15

what does 1,25-dihydroxyvitamin D do in the small intestine

Answer 15

diffuses into enterocytes where it binds to vitamin D receptors and increases gene expression
increases calcium absorption in small intestine

Question 16

what are negative feedback of second hydroxylation

Answer 16

decrease in FGF23 and 1,25-dihydroxyvitamin D

Question 17

1,25-dihydroxyvitamin D role in kidney

Answer 17

increases expression of Na-Pi cotransporters
improves PTH mediated Ca reabsorption

Question 18

1,25-dihydroxyvitamin D role in bone

Answer 18

increases number of osteoclasts

Question 19

where is calcitonin produced

Answer 19

clear cells of thyroid glands

Question 20

calcitonin responds to

Answer 20

hypercalaemia

Question 21

calcitonins role in bone

Answer 21

reduces rate of bone turnover and release of Ca from bone

Question 22

calcitonins role in kidneys

Answer 22

increase Ca excretion

Question 23

what do glucocorticoids regulate

Answer 23

bone density and intestinal Ca absorption

Question 24

parathyroid related proteins

Answer 24

mimics actions of PTH

Question 25

name the most studied phosphatonin

Answer 25

FGF23

Question 26

FGF23 stimulates

Answer 26

phosphate loss in urine

Question 27

How does FGF23 affect calcitriol (active vitamin D) production?

Answer 27

FGF23 decreases calcitriol production by inhibiting the enzyme 1α-hydroxylase in the kidneys

Question 28

what does FGF23 prevent

Answer 28

hyperphosphatemia

Question 29

what is hypocalcaemia

Answer 29

low plasma Ca

Question 30

signs and symptoms of hypocalcaemia

Answer 30

pins and needles muscle spasms paralysis convulsions

Question 31

what happens to voltage gated Na channels when Ca is low

Answer 31

open at resting membrane potential

Question 32

what is hypercalcaemia

Answer 32

high plasma Ca

Question 33

signs and symptoms of hypercalcaemia

Answer 33

bones stones grones and psychiatric overtones

Question 34

what is hypoparathyroidism

Answer 34

lack of PTH

Question 35

signs and symptoms of hypoparathyroidism

Answer 35

hypocalcaemia hyperphosphataemia muscle spasms

Question 36

what is hyperparathyroidism

Answer 36

excess of PTH

Question 37

What can cause hyperparathyroidism

Answer 37

tumors chronic kidney disease calcium malabsorption

Question 38

signs and symptoms of hyperparathyroidism

Answer 38

hypertension consitpation weakness hypercalcaemia confusion

Question 39

severe vitamin D deficiency can cause

Answer 39

osteomalacia rickets