Calcium Homeostasis

Question 1

Active form of calcium

Answer 1

Unionized calcium

Question 2

Key players in calcium homeostasis

Answer 2

Parathyroid hormone
Calcitonin
Vitamin d3

Question 3

Biochemical roles of calcium

Answer 3

Normal cell function
Neuromuscular excitability
Blood coagulation 
Hormonal secretion
Enzymatic regulation

Question 4

Most of calcium in the body is found in what form

Answer 4

Hydroxyapatite crystals

Question 5

Inorganic bone us composed of

Answer 5

Hydroxyapatite and organic matrix is composed of collagen

Question 6

2 major mechanisms of bone resorption

Answer 6

Osteocytic osteolysis and osteoclastic resorption

Question 7

Normal calcium concentration in the plasma

Answer 7

8.5 to 10mg/dL. (9.4mg/dL or 2.4mmol/L)

Question 8

Osteocytic osteolysis

Answer 8

Trans. From canaliculi to ecf via osteocytes. Removes calcium from recently formed crystals. fast

Question 9

Unlike osteocytic osteolysys,

Answer 9

Osteoclastic resorption destroys bone mass

Question 10

Intermittent administration of PTH and constant admisnistrstion of PTH

Answer 10

Bone growth and resorption

Question 11

Vitamin D function in bone regulation

Answer 11

Increases Ca2+ absorption from intestine and Ca2+ resorption from the bone

Question 12

Vitamin D is not a classic hormone because

Answer 12

It is not produced and secreted by an endocrine

Note. Not a true vitamin since it can be synthesized de novo.
Gotten from skin by Uv radiation and diet

Question 13

Previtamin D precursor?

Answer 13

7-dehydrocholestrol

Question 14

How do PTH and PO4 affect 1a-hydroxylase activitu

Answer 14

PTH stimulates in and increases 1,25 dihydroxy D

PO4 inhibits it and decreased PO4 levels stimulate 1a hydroxylase activity

Question 15

Activated vitamin D acts on osteo…

Answer 15

Blasts which have vitamin D receptors. These then activate osteoclasts to resorb Ca2+ from bone matrix

Question 16

PTH is produced in response to..

Answer 16

Low levels of Ca2+

Question 17

How is PTH regulated?

Answer 17

Decreased levels of calcium
Camp rises and pth secreted
Receptor within parathyroid gland membrane senses it
Inhibit adenyl cyclase pathway and activate phospholipase c pathway. Less camp produced and more ca2+ produced preventing pth from leaving by exocytosis

Question 18

Which enzymes does osteoclasts release in calcium bone resorption

Answer 18

Lysosomal enzymes collagenase and cathepsin

Question 19

Calcitonin major function

Answer 19

Decrease Ca2+levels

Question 20

Calcitonin secreted by

Answer 20

Parafollicular cells of the parathyroid gland

Question 21

Parafollicular cells distinct from thyroid follicular cells by

Answer 21

Large size, pale cytoplasm and small secretory granules