calcium physiology

Question 1

what are the functions of calcium?

Answer 1

bone & tooth structure
mineral store
AP (cardiac)
membrane excitability
2nd messenger
-muscle
-gland secretion
-non-steroid hormone action
co-factor in metabolic pathways
blood clotting

Question 2

what are the concentrations of ca?

Answer 2

diffusible:
ionised 1.2 mmol/l
bound to citrate 0.2mmol/l
non-diffusible:
bound to protein 1.2mmol/l

Question 3

what promotes calcium homeostasis?

Answer 3

PTH
calcitonin
vit. D

Question 4

how does PTH increase plasma Ca?`

Answer 4

raises reabsorption of bone
raises Ca2+ resorption in kidney
raises uptake of Ca2+ from intenstines

Question 5

how does calcitonin lower plasma Ca?

Answer 5

raises formation of bone
lowers Ca2+ resorption in kidney
not major role
secreted from thyroid in response to high plasma Ca2+

Question 6

which hormones increase bone formation and mass?

Answer 6

calcitonin
GH
IGF-1
insulin
iestrogen
testosterone

Question 7

which hormones increase bone resorption and decrease bone mass?

Answer 7

cortisol
PTH
thyroid hormones

Question 8

what are osteoblasts?

Answer 8

synthesise and secrete collagen fibres forming a matrix later mineralised

Question 9

what are osteocytes?

Answer 9

trapped osteoblasts in bone matrix

Question 10

what are osteoclasts?

Answer 10

large, multinucleate cells, derived from macrophages, that resorb bone

Question 11

what is hypo calcaemic tetany?

Answer 11

due to:
decreased Ca2+ intake
excessive Ca2+ loss
alkalosis- low Ca2+
low Ca2+ -> nerve excitability
pins & needles
muscle spasms
trousseaus sign
chvosteks sign

Question 12

what can cause alkalosis?

Answer 12

hyperventilation
by blowing off CO2
trap CO2 in lungs

Question 13

what is hyperparathyroidism?

Answer 13

osteitis fibrosa cystica

areas of demineralisation in skull and leg bones

Question 14

what is hypoparathyroidism?

Answer 14

defective mineralisation of teeth due to low blood calcium levels due to undersecretion of PTH

Question 15

what is vit. D deficiency?

Answer 15

dietary deficiency
failure to synthesis in body
low Ca uptake from GIT
unpermineralized bone
bone lacks rigidity
rickets-children
osteomalacia-adults

Question 16

what is osteoporosis?

Answer 16

reduced bone mass & density
loss of matrix w/ secondary loss of mineral
fractures common
common in elderly
evident earlier in women
causes: corticosteroids, menopause, nutritional deficiency

Question 17

what is osteopetrosis?

Answer 17

increased bone density & mass
reduced blood supply
prone to fracture and chronic infection
difficult extraction
tooth roots indistinct on xray
mandible > maxilla