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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
PTH regulates Pi levels by increasing what process in bone?
Increasing Pi resorption from bone
25
PTH regulates Pi levels by decreasing what process and increasing which process in kidneys?
Decreasing renal reabsorption of Pi, increasing its excretion
26
PTH regulates Pi levels by increasing what process in the gut?
gut absorption of Pi
27
What is the net effect of PTH?
Small decrease in plasma Pi levels
28
PTH increases intestinal absorption of Ca++ and Pi by activating _________ in the kidney?
Vitamin D
29
PTH puts more Ca++ into the blood, and more Pi into the urine by controlling....
their reabsorption in PCT of the kidney
30
PTH facilitates reabsorption of ___% of Ca++ which area of the nephron?
33%; thick ascending limb and distal tubule
31
PTH maintains dissimilar concentrations of Ca++ and Pi by what means?
Selectively inhibiting Pi reabsorption
32
PTH _____ Pi reabsorption from PCT and thus ______ excretion.
inhibits; increases
33
Pi excretion prevents what oppositional process?
Prevents simultaneous elevation of plasma Ca++ and Pi
34
PTH reduces the risk of CaPO4 ________ in soft tissues
precipitation
35
True/False: The purpose of PTH is to remodel bone?
FALSE!!! The purpose of PTH is NOT to remodel.
36
PTH acts on ______ primarily to regulate plasma levels of Ca/Pi
osteoblasts
37
If gut absorption does not attain normal ion levels, then PTH...
resorbs Ca/Pi from bone
38
PTH normally restores low plasma Ca++ levels by stimulating....
osteoclastic activity via RANK/RANKL
39
PTH action on bone maintains adequate normal Ca and Pi plasma levels for what purpose?
General functions, including bone deposition | But NOT for remodeling
40
PTH can have what two effects on Ca++/Pi in bone, depending on the PTH delivery?
resorb or deposit
41
Continuous PTH activity causes ______ bone resorption because it stimulates RANK/RANKL activation of osteoclasts, resulting in what condition?
Catabolic; hyperparathyroidism
42
Intermittent PTH activity stimulates ______ bone deposition.
anabolic
43
PTH pulse ____ the activity of osteoblasts and _____ their apoptosis, which occurs between bouts of PTH. (Possible medicinal application for osteoporosis)
increases; inhibits
44
Initial synthesis of vitamin D is in which two organs?
skin and liver
45
Vit D3 is synthesized in which part of the skin by what 2 items from the sun?
Epidermis; UV & IR
46
What form of Vit D is formed in the liver?
25(OH) D
47
Where is vitamin D activated?
in the kidney tubule
48
PTH facilitates formation of what form of Vit D in which area of the nephron?
1,25(OH)2 D in the PCT
49
Vit D_____ PTH release which is what kind of mechanism?
inhibits; negative feedback
50
What is the most important action of Vit D in the intestines?
Facilitate intestinal absorption of Ca/Pi
51
Vit D up-regulates what 2 things that carry Ca++ across the cell?
membrane Ca++ transporters and calbindin
52
Vit D up-regulation of membrane Ca++ transporters and calbindin prevents what?
Free Ca++ from triggering undesired cell functions
53
Vit D up-regulates the ___-___ cotransporter in intestinal cells
Na-PO4
54
True/False: The Na-PO4 cotransporter is more necessary if dietary levels are low.
True. Because high Pi levels enter passively paracellularly
55
True/False: Vit D effects on bone depends on which bony surface is involved
True
56
Cancellous (trabecular) bone has ____ activity while periosteal has ____ activity.
High; low
57
Vit D in cancellous bone causes resorption of Ca/Pi by activating which path?
osteoblast-RANKL-osteoclast path
58
Presence of Vit D in cancellous bone provides greater levels of plasma Ca/Pi for what purpose?
Deposition of bone in general
59
Vit D in periosteal stimulates _____, which increases strength in cortical bone and turns on bone formation mechanisms.
apposition
60
True/False: Bone formation depends on calcium stocks in bone
FALSE!!! Bone formation depends upon reservoir of Ca++ in blood
61
Which cells release calcitonin? From which gland?
parafollicular cells; thyroid gland
62
Calcitonin is released from parafollicular cells of the thyroid gland in response to what?
Increased Ca++ levels
63
Calcitonin ________ osteoclastic resorption of Ca++ & Pi from bone, thus favoring ________.
Inhibits; deposition
64
What two groups of people do we find calcitonin?
Lactating females (to protect against demineralization) and growing children
65
PTH and calcitonin act together to homeostatically do what?
maintain Ca++ levels at a tight equilibrium point
66
PTH _____ plasma Ca++ levels in response to a drop in Ca++ by stimulating _______ activity via paracrines (RANKL)
increases; osteoclastic
67
Calcitonin ______osteoclastic activity and thus _____ plasma Ca++ levels in response to an increase of Ca++
inhibits; decreases
68
Equilibrium point of calcitonin and PTH determines the levels of what?
plasma Ca++/Pi
69
Net loss of (HPO4)2- is due to...
Greater renal excretion relative to its plasma accumulation from bone resorption
70
Vitamin D has action in which 2 organs?
Intestine (absorb Ca++ & Pi) | Bone (resorb Ca++ & Pi)
71
PTH has action in which 3 organs?
Intestine (activate Vit D to absorb Ca++ & Pi) Kidney (reabsorb Ca++ & excrete Pi) Bone (resorb or deposit Ca++ & Pi)
72
Calcitonin has action in which organ?
Bone (inhibit resorption of Ca++ & Pi)
73
True/False: Equilibrium is a 50/50 ratio of Ca++ and Pi in the body
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
In hyperparathyroidism, PTH excess causes an increase in blood Ca++ due to increased what?
osteoclastic Ca++ resorption from bone
75
Excess calcium release from bone causes what conditions?
Bone weakness, kidney stones, depression of nervous system, constipation, abdominal pain, peptic ulcer, lack of appetite, depressed relaxation of heart during diastole
76
Pregnancy and lactation stimulate the PT glands (hyperparathyroidism) and predispose women to what condition
Tumor formation
77
In hypoparathyroidism, PTH deficiency causes a _______ in blood Ca++
decrease
78
Hypoparathyroidism is due to a reduction in what areas?
- Osteoclastic Ca++ resorption from bone - Absorption by intestine - Reabsorption by kidney
79
Hypoparathyroidism can cause what conditions?
tetany of muscles (esp. laryngeal muscles causing obstruction of respiration)
80
What is the condition that is demineralization of bone resulting from deficiency in Ca++ or Vit D?
Osteomalacia
81
In osteomalacia, kidney damage can diminish formation of what compound, which results in a reduction of gut absorption of Ca++.
1,25 DHCC (Vit D)
82
Which condition is a loss of bone matrix, not just loss of Ca++?
Osteoporosis
83
What are possible causes of osteoporosis?
hyperparathyroidism, inactivity of bones, lack of Vit C, postmenopausal lack of estrogen, lack of growth hormones (old age), hyperadrenalism (Cushing's)
84
Why can postmenopausal lack of estrogen cause osteoporosis?
estrogen normally stimulates osteoblasts
85
Why can hyperadrenalism (Cushing's disease) cause osteoporosis?
Cortisol decreases protein deposition in body (including bones)
86
Glucocorticoids are used to treat many disorders. Why is their use a drawback for the skeletal system?
They decrease bone formation by reducing the lifespan of osteoblasts and osteocytes
87
Use of glucocorticoids is the most frequent secondary cause of what other condition?
osteoporosis
88
What percent of patient taking glucocorticoids chronically experience fractures?
30-50%

Organ Systems Final (5 decks)

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