Calcium and Phosphate Flashcards Preview

Physiology Exam 2 Endocrine (Shelby) > Calcium and Phosphate > Flashcards

Flashcards in Calcium and Phosphate Deck (56)
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1
Q

The labile pool is in direct contact with the osteocytic-osteoblastic bone membrane which contains many _________ which is why Ca2+ can be released so quickly into the central canal

A

PTH activated Ca2+-ATPase pumps

2
Q

PTH activates vitamin D in the kidney my stimulating _______________ activity

A

stimulating 1-alpha hydroxylase

3
Q

In the cells, where is most of the phosphate (more than 80%)?

A

mitochondria

the rest is in the cytosol

4
Q

What do patients with Pseudohypoparathyroidism look like?

A

short stature
short neck
obese
shortened 4th metatarsal and metacarpal

5
Q

Which “pool” of the bone responds to acute changes and PTH stimulation

A

labile pool

6
Q

What enzyme converts vitamin D3 to 25-hydroxyvitamin D3?

By adding what?

A

25-hydroxylase

OH to Carbon 25

7
Q

Where is the first step of vitamin D activation?

A

liver

8
Q

What % of calcium in the plasma is in the ionized active form?

A

50%

9
Q

complications of hypoparathyroidism

A
  1. hypocalcemia induced tetany
  2. hyperreflexia
  3. spontaneous twitching
  4. muscle cramps
  5. convulsions
10
Q

Effects of excessive PTH-rp on the intestines

A

no intestinal effect

calcium uptake is not increased in the presence of PTH-rp

11
Q

increased cortisol or diabetes has what effect on PTH

A

increased

12
Q

increased phosphate excretion by the kidney can be measured by measuring ________ in the urine

A

cAMP

13
Q

Calcium is excreted mostly by the _____, and partially by the ______

A

mostly by the GI

partially by the kidney

14
Q

“stones, bones, and groans” =

A

primary hyperparathyroidism

15
Q

complications of Primary hyperparathyroidism

A
  1. osteoporosis, osteomalacia
  2. kidney stones
  3. muscle weakness
16
Q

Which “pool” of the bone undergoes resorption– slow breakdown of crystals and liberation of Ca and PO4 into the ECF

A

stable pool

17
Q

Effects of excessive PTH-rp

plasma Ca =
plasma PO43- =
plasma PTH =

A

plasma Ca = increased
plasma PO43- = decreased
plasma PTH = decreased

18
Q

The addition of ______ to _______ creates inactive vitamin D3

A

OH to carbon 24

24,25-dihydroxycholecalciferol

19
Q

What two effects does PTH have on the kidney?

What effect does it have in relation to the kidney that is not a “direct effect”

A
  1. stimulates Ca reabsorption
  2. inhibits PO4 reabsorption

PTH also activates vitamin D by stimulating 1-alpha hydroxylase activity in the kidney

20
Q

Vitamin D is inactive when it enters the blood from the skin or diet and it is called ___________

A

Vitamin D3

prohormone

21
Q

Effects of Pseudohypoparathyroidism

PTH =
serum Ca =
serum PO4 =

A

PTH = increased… but ineffective
serum Ca = decreased
serum PO4 = increased

22
Q

increased PTH = increase bone resorption = increased risk of

A

bone fracture

23
Q

Parathyroid gland release parathyroid hormone (PTH) from _______ cells

A

chief cells

24
Q

of the 1% of Ca2+ in the body that is not in the teeth and bone,

  1. 9% =
  2. 1 % =
A
  1. 9% = soft tissues, ER, mitochondria, membranes
  2. 1 % = plasma

(half of plasma is bound, half is free ionized)

25
Q

Vitamin D action on the bone:

A

synergizes with PTH to stimulate resorption and remodeling and to mobilize calcium and phosphate

26
Q

Ca10(PO4)6(OH)2 – hydroxyapatite

which bone “pool”?

A

stable pool

27
Q

Roles of phosphate:

A
  1. energy related pathways (metabolic)
  2. cofactors (NAD, etc)
  3. 2nd messengers
28
Q

Hypoparathyroidism is usually caused by

A

inadvertent consequence of thyroid surgery for treatment of cancer or Graves’ disease

29
Q

Effects of excessive PTH-rp

urine PO4 =
urine Ca2+ =
urine cAMP =

A

urine PO4 = increased
urine Ca2+ = increased
urine cAMP = increased

30
Q

what enzyme converts 25-hyroxyvitamin D3 to 1,25-dihydroxyvitamin D3?

By adding what?

A

1a-hydroxylase

OH to Carbon 1

31
Q

Primary hyperparathyroidism is most commonly caused by

A

PTH-secreting adenoma

32
Q

Vitamin D action on the kidney

A

calcium reabsorption

phosphate reabsorption

33
Q

If 1000mg of Ca2+ is ingested in the diet, what is the net absorption of Ca2+ (and eventually excreted by the kidney if Ca2+ levels are normal)

A

200 mg

which means 800mg is excreted by the GI

34
Q

What is the active hormone of vitamin D3?

A

1,25-dihydroxycholecalciferol
or
1,25-dihydroxyvitamin D3

35
Q

muscle weakness =
muscle tetany/hyperactive =

hypo/hyperparathyroidism?

A

muscle weakness = hyperparathyroidism

muscle tetany/hyperactive = hypoparathyroidism

36
Q

PTH on the kidney

plasma PO4 =
urine PO4 =
plasma Ca =
urine cAMP =

A

plasma PO4 = decrease
urine PO4 = increase
plasma Ca = increase
urine cAMP = increase

37
Q

Pseudohypoparathyroidism is also called

A

Albright’s hereditary osteodystrophy

38
Q

calcitonin decreases plasma Ca and PO4 by inhibiting:

A

bone resorption

tubular reabsorption

39
Q

CaHPO4:2H2O – amorphous crystals

which bone “pool”?

A

labile pool

40
Q

Phosphate distribution:

85% =
15% =

A
85% = bone and teeth
15% = muscle
41
Q

99% of Ca2+ is in ______ form found in the _____

A

crystalline

teeth and bone (1 and 2 kg)

42
Q

Primary hyperparathyroidism

Plasma Ca = 
Plasma PO43 = 
urine Ca = 
urine PO43 = 
urine cAMP =
A
Plasma Ca = increased
Plasma PO43 = decreased
urine Ca = increased ---(spills over!) 
urine PO43 = increased
urine cAMP = increased
43
Q

With normal Ca2+ intake, which form of vitamin D3 is produced?

A

inactive form

24,25-dihydroxycholecalciferol

44
Q

The __________ separates the bone itself from the plasma within the canals

A

osteocytic-osteoblastic bone membrane

45
Q

Activated vitamin D targets the intestine, bone, and kidney to collectively regulate __________ synthesis, and _____ and _____ levels in the plasma

A

calbindin synthesis

Ca2+ and PO43- levels in the plasma

46
Q

What is calbindin?

A

buffer protein of calcium in the intestines

47
Q

Total calcium free and bound in the blood =

A

~10mg/dL

48
Q

Where does the second step of vitamin D activation occur?

A

kidney

49
Q

What is the theorized reason for calcitonin

A

may protect against excessive bone resorption or when demand for Ca increases in pregnancy, lactation, and growth

50
Q

Hypoparathyroidism

Plasma PTH =
Plasma Ca =
Plasma PO4 =

A

Plasma PTH = decreased
Plasma Ca = decreased
Plasma PO43 = increased

phosphate cannot be excreted without PTH

51
Q

25-hydroxylase converts vitamin D3 to ________

in the liver

A

25-hydroxyvitamin D3

52
Q

calcitonin does not have an effect on _____ whereas PTH does

A

intestines

53
Q

PTH effect on labile pool of bone

A

osteolytic osteolysis for fast release of Ca and PO4 liberation into the ECF

54
Q

Humoral hypercalcemia of is caused by

A

malignant cell clusters that secrete PTH-related peptide (PTH-rp)

55
Q

Vitamin D action on the small intestine

A

increase expression of calbindin

increase calcium absorption

56
Q

excess vitamin D supplementation has what effect on PTH

A

decreased

but all the effects of PTH still exist from too much vitamin D