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Endocrine Physiology > Calcium Regulation > Flashcards

Calcium Regulation Flashcards

1
Q

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

A

Mineralization

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2
Q

______ is the principal circulating form of vitamin D.

A

25-hydroxycholecalciferol

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3
Q

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

A

increase

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4
Q

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

A

And

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5
Q

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

A

Vitamin D

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6
Q

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

A

Cholecalciferol

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7
Q

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

A

7- deydrocolesterol

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8
Q

Cholecalciferol is physiologically (active/inactive) _______.

A

Inactive

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9
Q

Cholecalciferol is hydroxylated in the liver to form __________.

A

25 hydroxycholecalciferol

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10
Q

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

A

Inactive

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11
Q

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

A

negative

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12
Q

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

A

alpha globulin

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13
Q

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

A

1, 25 dihydroxycholecalciferol or Calcitriol

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14
Q

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

A

1 alpha hydroxylase

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15
Q

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

A

Parathyroid hormone

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16
Q

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

________ by low concentrations of calcium and phosphate

A

stimulated

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17
Q

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

A

Calcium

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18
Q

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

A

phosphate

19
Q

Vitamin D is a (polypeptide/steroid)_______ hormone

A

steroid

20
Q

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

A

intestines

21
Q

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 ___________

A

Calbindin D 28K

22
Q

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

A

Calcitriol

23
Q

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

A

and

24
Q

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

A

Parathyroid hormone

25
Q

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

A

Ergocalciferol

26
Q

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

A

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

27
Q

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

A

Chief cells

28
Q

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

A

decreased

29
Q

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

A

Calcium sensing receptors

30
Q

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.

A

stimulates

31
Q

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

A

Magnesium

32
Q

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

A

Osteoblasts

33
Q

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

A

Osteoclasts

34
Q

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

A

Distal Convoluted Tubule

35
Q

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

A

Proximal convoluted tubule

36
Q

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

A

1 alpha hydroxylase

37
Q

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

A

RANKL

38
Q

Calcitonin’s major action is to inhibit ________.

A

Bone resorption by osteoclasts

39
Q

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

A

does not participate

40
Q

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

A

Parafollicular cells

41
Q

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

A

Calcium

42
Q

Normal blood calcium level should be between _________mg/dl

A

8.5 - 10 mg/dl

43
Q

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

A

Doesnt change

Endocrine Physiology (5 decks)

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