Calcium Homeostasis

Question 1

role of calcium

Answer 1

bone metabolism (calcium feeds into the skeletal structure of bone and makes hydroxyapatite)

Question 2

what type of receptor is the calcium sensing receptor?

Answer 2

GPCR

Question 3

where is the calcium sensing receptor found?

Answer 3

parathyroid hormones

Question 4

what happens when calcium binds to the receptor?

Answer 4

reduced PTH secretion

Question 5

what happens when there is no binding of calcium

Answer 5

signals low calcium levels in the blood so PTH is stimulated

Question 6

role of PTH

Answer 6

increases serum calcium
reduces serum phosphate
activates vitamin D in the kidneys

Question 7

how is PTH released from the parathyroid>

Answer 7

exocytosis

Question 8

what does PTH act on>

Answer 8

• bones
• kidneys
• intestines

Question 9

PTH action on bone

Answer 9

increases osteoclastic activity
reduces osteoblastic activity
releases more Ca2+ into the bloodstream from Ca3(PO4)2

Question 10

PTH action of the kidneys

Answer 10

reabsorption of calcium and increases blood concentration
excretion of phosphate in urine
vitamin D action

Question 11

PTH action on the intestines

Answer 11

reabsorption of calcium in the intestine requires vitamin D which is activated by the kidneys to calcitriol
calcitriol acts on the intestines to absorb calcium from food

Question 12

effect of high PTH on calcitriol

Answer 12

higher

Question 13

factors lowering vitamin D

Answer 13

low/poor intake (elderly, immigrants)
malabsorption due to disease
liver failure
kidney failure to phytate chapattis
pigment sunscreen
anticonvulsants

Question 14

vitamin D given in renal failure?

Answer 14

activated D3

Question 15

what does low vitamin D cause on the intestine

Answer 15

reduced absorption of calcium and phosphate in the intestine

PTH is increased leading to resorption of bone (Rickets and osteomalacia)

Question 16

what three hormones is calcium regulated by?

Answer 16

PTH
calcitonin
vitamin D

Question 17

what secretes calcitonin?

Answer 17

parafollicular C cells only in severe hypercalcaemia

Question 18

role of calcitonin

Answer 18

reduces bone resorption and decreases absorption in the intestines and kidneys (excreted)

Question 19

what activates vitamin D?

Answer 19

enzymes within the liver and kidneys

Question 20

function of calcium in the body

Answer 20

maintain bone strength
excitation in smooth and cardiac muscle
secretes peptides and hormones
excites neuromuscular junctions
role in blood clotting