Calcium Regulation

Question 1

When it comes to new bone, the role of vitamin D is to promote

Answer 1

Mineralization

Question 2

______ is the principal circulating form of vitamin D.

Answer 2

25-hydroxycholecalciferol

Question 3

The action of vitamin D is to (increase/decrease)______ both calcium and phosphate concentrations in plasma

Answer 3

increase

Question 4

Vitamin D increases the plasma concentration of calcium (and/but not of)_______ phosphate.

Answer 4

And

Question 5

The second major regulator of calcium and phosphate metabolism (after parathyroid hormone) is ______.

Answer 5

Vitamin D

Question 6

Vitamin D3, which can be acquired from milk in the diet, is known as ________.

Answer 6

Cholecalciferol

Question 7

Cholecalciferol is produced in the skin from______ in the presence of ultraviolet light, and also acquired from diet.

Answer 7

7- deydrocolesterol

Question 8

Cholecalciferol is physiologically (active/inactive) _______.

Answer 8

Inactive

Question 9

Cholecalciferol is hydroxylated in the liver to form __________.

Answer 9

25 hydroxycholecalciferol

Question 10

25-hydroxycholecalciferol is physiologically (active/inactive) _______.

Answer 10

Inactive

Question 11

The hydroxylation of cholecalciferol is regulated by (positive/negative)_________ feedback mechanisms.

Answer 11

negative

Question 12

25-hydroxycholecalciferol is bound to a/an ___________ in plasma.

Answer 12

alpha globulin

Question 13

In the kidneys 25-hydroxycholecalciferol can be hydroxylated at the carbon-1 position to the active form known as _________.

Answer 13

1, 25 dihydroxycholecalciferol or Calcitriol

Question 14

The enzyme ________ is responsible for the hydroxylation step necessary to produce 1,25-(OH)2-cholecalciferol from 25-hydroxycholecalciferol.

Answer 14

1 alpha hydroxylase

Question 15

The enzyme 1-alpha-hydroxylase is stimulated by (hormone) _________.

Answer 15

Parathyroid hormone

Question 16

The enzyme 1-alpha-hydroxylase is (stimulated/inhibited)

________ by low concentrations of calcium and phosphate

Answer 16

stimulated

Question 17

Low concentrations of _______ and phosphate stimulate the enzyme 1-alpha-hydroxylase.

Answer 17

Calcium

Question 18

Decreased plasma calcium and ________ concentration stimulate the enzyme 1-alpha-hydroxylase.

Answer 18

phosphate

Question 19

Vitamin D is a (polypeptide/steroid)_______ hormone

Answer 19

steroid

Question 20

The major actions of 1,25-dihydroxycholecalciferol are on the ________ , kidneys and bones.

Answer 20

intestines

Question 21

On the intestine, 1,25-dihydroxycholecalciferol increases calcium and phosphate absorption, by inducing the synthesis of a vitamin D-dependent calcium-binding protein known as ___________

Answer 21

Calbindin D 28K

Question 22

Calbindin D-28K is the calcium-binding protein induced by ________ in the intestine.

Answer 22

Calcitriol

Question 23

1,25-dihydroxycholecalciferol action on the kidney is to stimulate calcium (and/but not) ________ phosphate absorption.

Answer 23

and

Question 24

In bone, 1,25-dihydroxycholecalciferol acts together with _______ to stimulate osteoclast activity and bone resorption.

Answer 24

Parathyroid hormone

Question 25

Vitamin D2, which can be acquired from plant foods in the diet, is known as _________.

Answer 25

Ergocalciferol

Question 26

The concentration of calcium in extracellular fluid is regulated by _______ hormone.

Answer 26

Parathyroid Hormone (Vitamin D and Calcitonin also regulate Calcium levels)

Question 27

Parathyroid hormone is synthesized in _______ cells of the parathyroid gland.

Answer 27

Chief cells

Question 28

When plasma calcium concentrations are (increased/decreased) _________ , parathyroid hormone is stimulated to return them to normal levels.

Answer 28

decreased

Question 29

The parathyroid gland uses _________ receptors, in which calcium binds to and activates phospholipase C.

Answer 29

Calcium sensing receptors

Question 30

When there are low extracellular calcium levels, less calcium binds to the calcium-sensing receptors and this in turn (inhibits/stimulates)________ the release of parathyroid hormone.

Answer 30

stimulates

Question 31

An ion that is a cofactor in the stimulation of parathyroid hormone secretion is ___________.

Answer 31

Magnesium

Question 32

Parathyroid hormone receptors are found on (osteoblasts/osteoclasts) __________.

Answer 32

Osteoblasts

Question 33

Parathyroid hormone acts on osteoblasts, which release cytokines that stimulate _________ , which increase bone resorption to release calcium into the blood.

Answer 33

Osteoclasts

Question 34

Parathyroid hormone acts to increase renal reabsorption of calcium in the ________ tubule.

Answer 34

Distal Convoluted Tubule

Question 35

Parathyroid hormone acts to decrease renal reabsorption of phosphate in the _______ tubule.

Answer 35

Proximal convoluted tubule

Question 36

Parathyroid hormone acts to increase calcitriol by stimulating ________ in the proximal convoluted tubule.

Answer 36

1 alpha hydroxylase

Question 37

Parathyroid hormone increases production of (ligand) _______ to eventually increase calcium and bone resorption.

Answer 37

RANKL

Question 38

Calcitonin's major action is to inhibit ________.

Answer 38

Bone resorption by osteoclasts

Question 39

Calcitonin, unlike parathyroid hormone, (participates/does not participate) _________ in the minute-to-minute regulation of plasma calcium concentration.

Answer 39

does not participate

Question 40

Calcitonin is synthesized and secreted by the _________ or C cells of the thyroid gland.

Answer 40

Parafollicular cells

Question 41

Calcitonin is stored in granules, and released when plasma concentration of ________ increases.

Answer 41

Calcium

Question 42

Normal blood calcium level should be between _________mg/dl

Answer 42

8.5 - 10 mg/dl

Question 43

In most people, if the thyroid gland is removed, the level of blood calcium (increases/decreases/doesn't change) __________

Answer 43

Doesnt change