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Physio II (Exam 3) > TOPIC 11 Control of K, Ca, Phosphate and Mg > Flashcards

TOPIC 11 Control of K, Ca, Phosphate and Mg Flashcards

1
Q

Total calcium in plasma: mEq/liter

A

Total calcium in plasma: 5 mEq/liter

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2
Q

Total calcium in plasma: % distribution ionized, non-ionized and bound ?

A

50% in ionized form
40% bound to plasma protein
Amount bound to protein decreases with an increase in [H+]. Patients with alkalosis more susceptible to hypocalcemic tetany
10% bound in non-ionized form to other ions (phosphate, citrate)

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3
Q

Amount of Ca bound to protein decreases with an increase in what ion?
what patients are more susceptible to this?

A

[H+]. Patients with alkalosis more susceptible to hypocalcemic tetany

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4
Q

Ca Normal ion concentration: mEq/liter

A

2.4 mEq/liter (1.2 mmol/liter)

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5
Q

Hypocalcemia:

A

increases muscle and nerve excitability (hypocalcemic tetany)

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6
Q

Hypercalcemia

A

depressed neuromuscular excitability which

can lead to cardiac arrhythmias

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7
Q

99% of calcium stored where?

A

bone
HUGE reservoir–if plasma concentration drops, body will move calcium from the bone
–if plasma concentration rises, body will move calcium back into the bone

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8
Q

% Ca present in intracellular space and cell organelles

A

1%

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9
Q

% Ca present in extracellular fluid

A

0.01%

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10
Q

Parathyroid Hormone As with all ions, intake and output must be matched over time, with output changing to match match what?

A

to match the input

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11
Q

PTH most important control agent for what?

A

calcium

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12
Q

How is Parathyroid Hormone excreted?

A

90% excreted via gastrointestinal tract (feces) (≈900 mg/day)
10% excreted via kidneys (urine) (≈100 mg/day)

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13
Q

PTH regulation accomplished through 3 actions: (stimulations)

A

Stimulation of bone resporption of calcium
Stimulation of vitamin D which stimulates calcium reabsorption by intestines
Direct stimulation of renal tubule reabsorption of calcium

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14
Q

As extracellular calcium concentration falls: what is the parathyroid gland stimulated to do?
which does what?

(this is in regard to the bones)

A

Parathyroid gland directly stimulated to increase secretion of PTH
Increased PTH concentration stimulates bone to increase release of bone salts (resporption) which includes the release of large amounts of calcium

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15
Q

As extracellular calcium concentration increases: what does the parathyroid gland do? which does what?

(this is in regard to the bones)

A

Parathyroid gland decreases PTH secretion
Decreased PTH concentration decreases salt
resporption to point where calcium will be added to the bone

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16
Q

Difference between resp acidosis

A

increasing Volume of H+ with an end production of CO2

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17
Q

When will we see phosphate in our urine?

A

if we have a higher than normal concentration and it exceeds our ability to reabsorb (Tmax

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18
Q

Ca excretion rate ?

how much of body’s Ca are we actually filtering ?

A

Freely filtered, reabsorbed BUT NOT secreted
Excretion rate = Filtration–Reabsorption
Only filtering a very small percentage of the calcium that is actually present in the body!!!!!

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19
Q

% Ca filtered load reabsorbed in the proximal tubule:

A

65% filtered load reabsorbed

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20
Q

% Ca filtered load reabsorbed in the LOH?

A

25 to 30% filtered load reabsorbed

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21
Q

% Ca filtered load reabsorbed in Distal tubule / Collecting tubule

A

4 to 9% filtered load reabsorbed

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22
Q

% of Ca filtered load normally excreted?

A

Normally only 1% is excreted

Changes as plasma concentration changes (i.e. intake changes)

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23
Q

Ca reabsorbed in the proximal tubule % carried via paracellular pathway and transcellular pathway ?

A

80% of amount reabsorbed carried by water via paracellular pathway
20% of amount reabsorbed via a transcellular pathway

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24
Q

Ca reabsorbed via transcellular pathway works how? diffusion driven by what? and pumped out via what?

In Proximal Tubule

A

Diffusion through luminal membrane into cell driven by chemical gradient (higher [Ca++] in lumen than inside cell) AND by electrical gradient (interior of cell negative with respect to lumen
Pumped out of cell across basolateral membrane via Ca ATPase pump and Na-Ca counter-transport mechanism

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25
Q

Ca % of reabsorption by paracellular pathway ?

In Thick Ascending Loop of Henle

A

Paracellular pathway accounts for 50% of reabsorption in loop
Transcellular pathway accounts for 50% of reabsorption in loop

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26
Q

Ca reabsorbed by paracellular pathway — via how?

In Thick Ascending Loop of Henle

A

Passive diffusion down electrical gradient–lumen has slight positive charge compared to interstitial fluid

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27
Q

Ca reabsorbed by Transcellular pathway – what process?

In Thick Ascending Loop of Henle

A

Active process stimulated by PTH, Vitamin D (Calcitrol), and calcitonin (PTH concentration most important)

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28
Q

In the Distal Tubulal - Ca Reabsorption is transported almost all via what pathway? and what type of transport is it?

A

Almost all transport via Transcellular pathway
Active transport across basolateral membrane –diffusion into cell
Increased [PTH] increases Ca ++ reabsorption
Reabsorption also increased by Vitamin D and calcitonin

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29
Q

In the Distal Tubulal - increased PTH does what to Ca++?

A

Increased [PTH] increases Ca++reabsorption

Reabsorption also increased by Vitamin D and calcitonin

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30
Q

PTH is a Primary controller of what?

A

Regulation of Ca++Reabsorption / Excretion

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31
Q

INCREASED Ca reabsorption means there is an increase in what 2 other things too?

A

From an ⬆️ PTH and there is an increase with that Plasma Phosphate

Vit D3

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32
Q

INCREASED Ca reabsorption caused by a decrease in what?

A

Caused by a ⬇️ BP and ECFV

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33
Q

INCREASED Ca reabsorption caused by what kind of acid base status ?

A

Metabolic Acidosis

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34
Q

Decreased Ca reabsorption caused by increase in what 2 things ?

A

⬆️ BP and ECFV

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35
Q

Decreased Ca reabsorption caused by a decrease in what?

A

⬇️ PTH and goes along decrease Plasma Phosphate

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36
Q

Decreased Ca reabsorption caused what kind of acid base status ?

A

Metabolic Alkalosis

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37
Q

PTH has no effect in what Tubule
(Following sodium and water
reabsorption)

A

in Proximal Tubule

Following sodium and water reabsorption

38
Q

[Phosphate] affects [PTH]–As [Phosphate] increases, [PTH] does what?

A

increases

39
Q

[H+] major affect is on the transport

mechanisms in what Tubule?

A

Distal Tubule

40
Q

If filtered load under Tmax, all phosphate is what?

A

all phosphate reabsorbed

41
Q

If filtered load over Tmax, phosphate is what?

A

phosphate is excreted

42
Q

Phosphate Plasma threshold level is approx? mMol/L

Phosphate Normal plasma concentration around mMol/liter?

A

-0.8 mMol/liter
-1 mMol/liter
–Large intake of phosphate each day (milk & meat)

43
Q

Proximal Tubule: % of of filtered phosphate reabsorbed

A

75 to 80%

Enters cells from lumen via Na
-Phosphate co-transport mechanism
Leaves cell via counter-transport mechanism across basolateral membrane

44
Q

Phosphate reabsorbed into Proximal Tubule by what transport mechanism?

A

Phosphate co-transport mechanism

Leaves cell via counter-transport mechanism across basolateral membrane

45
Q

Phosphate reabsorbed amount in LOH?

A

Loop of Henle: Very small amounts

46
Q

Phosphate reabsorbed amount in Distal Tubule?

A

10% of filtered phosphate reabsorbed

47
Q

Phosphate reabsorbed amount in Collecting Tubule?

A

Very small amounts

48
Q

Approximately what % of filtered phosphate is excreted?

A

10%

49
Q

Phosphate Tmax can change based on what?

A

intake

-Low intake, Tmax will increase over time

50
Q

As PTH increases bone resorption of what two other substances are also reSORBED?

A

calcium & phosphate are also resorbed

51
Q

Magnesium - where is it stored/located?

A

> 50% stored in bone
Most of what is left is located in the intracellular volume
<1% located in extracellular volume

52
Q

Renal excretion of magnesium is ≈ what % of filtered load?

A

10 to 15% of filtered load

53
Q

TOTAL plasma magnesium = 1.8 mEq/liter BUT what % is bound? making what new amount free?

A

> 50% is bound to plasma proteins so free ionized is 0.8 mEq/liter

54
Q

What % of Mg is absorbed in the GI tract?

A

only 50% is actually absorbed by the gastrointestinal tract

55
Q

What % of filtered load of Mg is reabsorbed in the Proximal Tubule?

A

Proximal Tubule: 25% of filtered load

56
Q

What % of filtered load of Mg is reabsorbed in the Loop of Henle?

A

Primary site of reabsorption–65% of filtered load

57
Q

What % of filtered load of Mg is reabsorbed in the Distal Tubule / Collecting Tubule?

A

<5% of filtered load

58
Q

⬆️ [Magnesium] results in what to reabsorption and excretion?

A

⬇️ reabsorption and ⬆️ excretion

59
Q

⬆️ EC fluid volume results in what to reabsorption and excretion?

A

⬇️ reabsorption and ⬆️ excretion

60
Q

⬆️ [Ca++] results in what to reabsorption and excretion?

A

⬇️ reabsorption and ⬆️ excretion

61
Q

K levels fluctuations?

A

Tightly controlled

–Usually changes less than ± 0.3 mEq/liter

62
Q

K amount %’s in intracellular & extracellular spaces?

A

98% located intracellular volume

–only 2% extracellular

63
Q

K first line of defense against changes in

extracellular concentration?

A

Movement between intra and

extracellular compartments possible

64
Q

K elimination how?

A

Only 5 to 10% of intake removed by feces

–rest must be removed by kidneys

65
Q

Insulin moves what 2 things into the cells following a meal?

A

potassium AND glucose

66
Q

Factors that shifts K+ into cells (Potential hypo) (4)

A

Insulin
Aldosterone (also increase K secretion)
Alkalosis
Β-adrenergic stimulation

67
Q

Factors that shifts K+ out of cells (Potential hyper) (7)

A 
Insulin deficiency 
Aldosterone deficiency
Acidosis
B-adrenergic blockade
Cell lysis
Strenuous exercise
Increased extracellular fluid osmolarity
68
Q

Epinephrine stimulates β2-adrenergic receptors increasing movement of K+ where?

A

into the cell.

69
Q

β2-adrenergic blocking agents treats what? and can lead to what?

A

hypertension) can lead to hyperkalemia

70
Q

Increased [H+] will reduce action of Na-K ATPase with less transfer of what into the cells?

A

K+ into the cells

71
Q

With an increase in extracellular K osmolarity, water moves out of the cell increasing _____ [K+] which increases the rate of K+ diffusion ______

A

intracellular

out of the cell

72
Q

Consistent Reabsorption of K % in proximal tubule?

A

65%

73
Q

Consistent Reabsorption of K % loop (mainly thick ascending segment)?

A

25 to 30%

74
Q

With normal K+ intake of 100 mEq/day what would feces and kidneys remove?

A

Feces removes 8 mEq

Kidneys must remove 92 mEq

75
Q

High potassium intake
Distal tubule & cortical collecting tubule
increase potassium what?

A

increase potassium secretion

Very strong mechanism–rate of potassium excretion can exceed amount of potassium being filtered

76
Q

Low potassium intake – Secretion rate does what?

A

decreases

Can decrease secretion to point where there is net reabsorption
Excretion can fall to 1% of filtered potassium (756 mEq/day x 0.01 = 8mEq/day)

77
Q

Principal Cells

Make up what % of cells in late distal and cortical collecting tubule?

A

90%

78
Q

Intercalated Cells Reabsorb what?

In distal tubule and cortical collecting duct

A

Reabsorb potassium especially during potassium depletion

79
Q

H-K ATPase
located where? and pumps what which ways?
All taking place in distal and cortical collecting duct

A

Located tubular membrane
Pumps H+ from tubular cell into lumen (secretion)
Pumps K+ from tubular lumen into cell (reabsorption)
K+ diffuses from cell into interstitial space via basolateral membrane

80
Q

H-K ATPase major effect only during what depletion?

In distal and cortical collecting duct

A

Major effect only during potassium depletion

81
Q

Increased [H+] will do what to potassium secretion?

In distal and cortical collecting ducts

A

DECREASE

82
Q

Stimulation of Potassium Secretion by what 3 things?

In distal tubules and cortical collecting ducts

A

Increased extracellular [K+]
Increased [aldosterone]
Increased tubular flow rate

83
Q

Increased aldosterone increases rate of sodium reabsorption by what parts of the nephron?

A

late distal tubule and collecting duct

84
Q

[K+] of renal interstitial fluid increases (increased plasma concentration) which
decreases amount of K+ diffusing from cell interior _____

A

into interstitial space

85
Q

Plasma Potassium & Aldosterone

Great example of _____ control system

A

negative feedback

Factor being controlled (potassium) as feedback effect on controller (aldosterone)

86
Q

Small change in plasma [K+] produced __ change in aldosterone concentration

A

huge

Normal aldosterone level is approximately 6 nag/dL

87
Q

Anything that affects our ability to produce aldosterone will have a big effect on ____ excretion!!

A

potassium

88
Q

High aldosterone (primary aldosteronism) — ___kalemia

A

Hypokalemia

89
Q

Low aldosterone (Addison’s disease)- ___kalemia

A

Hyperkalemia

90
Q

Acidosis (___ H+) _____ potassium secretion

A

(INCREASED H+) reduces potassium secretion
Reduces the activity of Na-K ATPase–decreases driving force for moving potassium from cell interior to tubular lumen
Prolonged acidosis produces increased potassium excretion
–Result of decreased reabsorption of sodium
chloride and water in proximal tubule and increased distal tubular flow

91
Q

Alkalosis (___ H+) _____ potassium secretion

A

( Decreases H+) increases potassium secretion

92
Q

Increased distal tubular flow rate will ____ potassium secretion?

A

increase

Increased tubular flow rate can be caused by volume expansion; high sodium intake; specific diuretics

Physio II (Exam 3) (6 decks)

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