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Organ Systems Final > Ca+ and Phosphate Regulation > Flashcards

Ca+ and Phosphate Regulation Flashcards

0
Q

What percent of Ca+ in the blood is protein-bound?

A

40%

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1
Q

Ca+ concentration is one of the most closely regulated parameters in the body, varying only __-__% daily or weekly

A

1-2%

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2
Q

What percent of Ca+ in the blood is filterable through the kidneys?

A

60%

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3
Q

What percent of Ca+ from the blood that gets filtered through the kidneys is bound to anions? Which anions?

A

10%; phosphate, sulfate, and citrate

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4
Q

What is the biologically active form of Ca++? Which hormone controls it?

A

Free, ionized Ca++; parathyroid hormone

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5
Q

Plasma levels of the biologically active ionized Ca++ are buffered by…

A

proteins, phosphate, and H+

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6
Q

What ion competes with Ca++ for sites on proteins?

A

H+

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7
Q

What condition results when excess H+ ions occupy sites on proteins? This leads to…

A

Acidosis; increasing levels of free, ionized Ca++

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8
Q

What is the result of acidosis?

A

Decreases neural activity and causes muscle weakness

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9
Q

What condition results when deficient H+ ions permits Ca++ binding to proteins? Leading to…

A

Alkalosis; reducing levels of free ionized Ca++

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10
Q

What is the result of alkalosis?

A

Neuromuscular irritability (numbness, tingling, muscle tetany) and CNS problems

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11
Q

Ca+ levels are homeostatically maintained by mechanisms in which 3 organs?

A

kidney, bone, and gut (intestines)

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12
Q

To maintain enough Ca++ and Pi for bone mineralization homeostatically, what are the 3 primary hormones used?

A
  • Parathyroid (PTH)
  • Vitamin D
  • Calcitonin (to a lesser extent)
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13
Q

Hormones control Ca++ and Pi absorption in which organ?

A

intestine

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14
Q

Hormones control Ca++ and Pi resorption in which organ?

A

bone

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15
Q

Hormones control Ca++ and Pi reabsorption in which organ?

A

kidney

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16
Q

Parathyroid hormone (PTH) is secreted from which gland and where are they located?

A

Parathyroid gland; posterior surface of thyroid

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17
Q

What is the result of accidental removal of parathyroid glands during thyroid surgery?

A

hypoparathyroidism

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18
Q

True/False: PTH regulates calcium and phosphate by acting on kidney, intestines, and bone.

A

True

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19
Q

CaSR (Calcium sensing receptor) in the parathyroid gland respond to a drop in free ionized Ca++ by…

A

releasing PTH

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20
Q

What is the primary purpose of PTH?

A

Bring more Ca++ into the system

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21
Q

PTH increases Ca++ levels by increasing what process in bone?

A

Bone resorption to release Ca++ and Pi

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22
Q

PTH increases Ca++ levels by increasing what process in kidneys?

A

Renal Ca++ reabsorption

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23
Q

PTH increases Ca++ levels by increasing what process in gut? Via what compound?

A

Gut absorption of Ca++ via Vitamin D

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24
Q

PTH regulates Pi levels by increasing what process in bone?

A

Increasing Pi resorption from bone

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25
Q

PTH regulates Pi levels by decreasing what process and increasing which process in kidneys?

A

Decreasing renal reabsorption of Pi, increasing its excretion

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26
Q

PTH regulates Pi levels by increasing what process in the gut?

A

gut absorption of Pi

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27
Q

What is the net effect of PTH?

A

Small decrease in plasma Pi levels

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28
Q

PTH increases intestinal absorption of Ca++ and Pi by activating _________ in the kidney?

A

Vitamin D

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29
Q

PTH puts more Ca++ into the blood, and more Pi into the urine by controlling….

A

their reabsorption in PCT of the kidney

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30
Q

PTH facilitates reabsorption of ___% of Ca++ which area of the nephron?

A

33%; thick ascending limb and distal tubule

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31
Q

PTH maintains dissimilar concentrations of Ca++ and Pi by what means?

A

Selectively inhibiting Pi reabsorption

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32
Q

PTH _____ Pi reabsorption from PCT and thus ______ excretion.

A

inhibits; increases

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33
Q

Pi excretion prevents what oppositional process?

A

Prevents simultaneous elevation of plasma Ca++ and Pi

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34
Q

PTH reduces the risk of CaPO4 ________ in soft tissues

A

precipitation

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35
Q

True/False: The purpose of PTH is to remodel bone?

A

FALSE!!! The purpose of PTH is NOT to remodel.

36
Q

PTH acts on ______ primarily to regulate plasma levels of Ca/Pi

A

osteoblasts

37
Q

If gut absorption does not attain normal ion levels, then PTH…

A

resorbs Ca/Pi from bone

38
Q

PTH normally restores low plasma Ca++ levels by stimulating….

A

osteoclastic activity via RANK/RANKL

39
Q

PTH action on bone maintains adequate normal Ca and Pi plasma levels for what purpose?

A

General functions, including bone deposition

But NOT for remodeling

40
Q

PTH can have what two effects on Ca++/Pi in bone, depending on the PTH delivery?

A

resorb or deposit

41
Q

Continuous PTH activity causes ______ bone resorption because it stimulates RANK/RANKL activation of osteoclasts, resulting in what condition?

A

Catabolic; hyperparathyroidism

42
Q

Intermittent PTH activity stimulates ______ bone deposition.

A

anabolic

43
Q

PTH pulse ____ the activity of osteoblasts and _____ their apoptosis, which occurs between bouts of PTH. (Possible medicinal application for osteoporosis)

A

increases; inhibits

44
Q

Initial synthesis of vitamin D is in which two organs?

A

skin and liver

45
Q

Vit D3 is synthesized in which part of the skin by what 2 items from the sun?

A

Epidermis; UV & IR

46
Q

What form of Vit D is formed in the liver?

A

25(OH) D

47
Q

Where is vitamin D activated?

A

in the kidney tubule

48
Q

PTH facilitates formation of what form of Vit D in which area of the nephron?

A

1,25(OH)2 D in the PCT

49
Q

Vit D_____ PTH release which is what kind of mechanism?

A

inhibits; negative feedback

50
Q

What is the most important action of Vit D in the intestines?

A

Facilitate intestinal absorption of Ca/Pi

51
Q

Vit D up-regulates what 2 things that carry Ca++ across the cell?

A

membrane Ca++ transporters and calbindin

52
Q

Vit D up-regulation of membrane Ca++ transporters and calbindin prevents what?

A

Free Ca++ from triggering undesired cell functions

53
Q

Vit D up-regulates the ___-___ cotransporter in intestinal cells

A

Na-PO4

54
Q

True/False: The Na-PO4 cotransporter is more necessary if dietary levels are low.

A

True. Because high Pi levels enter passively paracellularly

55
Q

True/False: Vit D effects on bone depends on which bony surface is involved

A

True

56
Q

Cancellous (trabecular) bone has ____ activity while periosteal has ____ activity.

A

High; low

57
Q

Vit D in cancellous bone causes resorption of Ca/Pi by activating which path?

A

osteoblast-RANKL-osteoclast path

58
Q

Presence of Vit D in cancellous bone provides greater levels of plasma Ca/Pi for what purpose?

A

Deposition of bone in general

59
Q

Vit D in periosteal stimulates _____, which increases strength in cortical bone and turns on bone formation mechanisms.

A

apposition

60
Q

True/False: Bone formation depends on calcium stocks in bone

A

FALSE!!! Bone formation depends upon reservoir of Ca++ in blood

61
Q

Which cells release calcitonin? From which gland?

A

parafollicular cells; thyroid gland

62
Q

Calcitonin is released from parafollicular cells of the thyroid gland in response to what?

A

Increased Ca++ levels

63
Q

Calcitonin ________ osteoclastic resorption of Ca++ & Pi from bone, thus favoring ________.

A

Inhibits; deposition

64
Q

What two groups of people do we find calcitonin?

A

Lactating females (to protect against demineralization) and growing children

65
Q

PTH and calcitonin act together to homeostatically do what?

A

maintain Ca++ levels at a tight equilibrium point

66
Q

PTH _____ plasma Ca++ levels in response to a drop in Ca++ by stimulating _______ activity via paracrines (RANKL)

A

increases; osteoclastic

67
Q

Calcitonin ______osteoclastic activity and thus _____ plasma Ca++ levels in response to an increase of Ca++

A

inhibits; decreases

68
Q

Equilibrium point of calcitonin and PTH determines the levels of what?

A

plasma Ca++/Pi

69
Q

Net loss of (HPO4)2- is due to…

A

Greater renal excretion relative to its plasma accumulation from bone resorption

70
Q

Vitamin D has action in which 2 organs?

A

Intestine (absorb Ca++ & Pi)

Bone (resorb Ca++ & Pi)

71
Q

PTH has action in which 3 organs?

A

Intestine (activate Vit D to absorb Ca++ & Pi)
Kidney (reabsorb Ca++ & excrete Pi)
Bone (resorb or deposit Ca++ & Pi)

72
Q

Calcitonin has action in which organ?

A

Bone (inhibit resorption of Ca++ & Pi)

73
Q

True/False: Equilibrium is a 50/50 ratio of Ca++ and Pi in the body

A

FALSE!!! Balance is NOT 50/50. Ca+ levels will be much higher. Balance is a homeostasis for proper function. You will always excrete more Pi than Ca++.

74
Q

In hyperparathyroidism, PTH excess causes an increase in blood Ca++ due to increased what?

A

osteoclastic Ca++ resorption from bone

75
Q

Excess calcium release from bone causes what conditions?

A

Bone weakness, kidney stones, depression of nervous system, constipation, abdominal pain, peptic ulcer, lack of appetite, depressed relaxation of heart during diastole

76
Q

Pregnancy and lactation stimulate the PT glands (hyperparathyroidism) and predispose women to what condition

A

Tumor formation

77
Q

In hypoparathyroidism, PTH deficiency causes a _______ in blood Ca++

A

decrease

78
Q

Hypoparathyroidism is due to a reduction in what areas?

A
  • Osteoclastic Ca++ resorption from bone
  • Absorption by intestine
  • Reabsorption by kidney
79
Q

Hypoparathyroidism can cause what conditions?

A

tetany of muscles (esp. laryngeal muscles causing obstruction of respiration)

80
Q

What is the condition that is demineralization of bone resulting from deficiency in Ca++ or Vit D?

A

Osteomalacia

81
Q

In osteomalacia, kidney damage can diminish formation of what compound, which results in a reduction of gut absorption of Ca++.

A

1,25 DHCC (Vit D)

82
Q

Which condition is a loss of bone matrix, not just loss of Ca++?

A

Osteoporosis

83
Q

What are possible causes of osteoporosis?

A

hyperparathyroidism, inactivity of bones, lack of Vit C, postmenopausal lack of estrogen, lack of growth hormones (old age), hyperadrenalism (Cushing’s)

84
Q

Why can postmenopausal lack of estrogen cause osteoporosis?

A

estrogen normally stimulates osteoblasts

85
Q

Why can hyperadrenalism (Cushing’s disease) cause osteoporosis?

A

Cortisol decreases protein deposition in body (including bones)

86
Q

Glucocorticoids are used to treat many disorders. Why is their use a drawback for the skeletal system?

A

They decrease bone formation by reducing the lifespan of osteoblasts and osteocytes

87
Q

Use of glucocorticoids is the most frequent secondary cause of what other condition?

A

osteoporosis

88
Q

What percent of patient taking glucocorticoids chronically experience fractures?

A

30-50%

Organ Systems Final (5 decks)

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