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RENAL > VI: Acid-Base Physiology > Flashcards

VI: Acid-Base Physiology Flashcards

1
Q

Acidemia range

A

pH<7.35

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2
Q

Alkalemia range

A

pH>7.45

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3
Q

Intracellular and extracellular pH

A 
Intracellular pH (7.2) < Extracellular pH
Intracellular pH is more acidic
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4
Q

Arterial pH is slightly

A

Alkaline, pH=7.4

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5
Q

Volatile acid definition

A

CO2, produced during digestion (end product of metabolism)

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6
Q

Nonvolatile acid definition

A

Produced from incomplete metabolism

EX. lactic acid

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7
Q

Excretion of volatile acids by

A

Lungs

CO2

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8
Q

Excretion of nonvolatile acids by

A

Kidney

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9
Q

Volatile acid into bicarbonate

A

CO2 + H2O H2CO3 HCO3- + H+

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10
Q

Enzyme involved in the reaction of CO2 into bicarbonate

A

Carbonic anhydrase

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11
Q

Under pathophysiologic states, B-hydroxybutyric acid and acetoacetic acid formed from

A

Untreated diabetes mellitus

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12
Q

Under pathophysiologic states, lactic acid formed from

A

Exercise and hypoxic tissue

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13
Q

Under pathophysiologic states, salicylic acid formed from

A

Aspirin overdose

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14
Q

Under pathophysiologic states, formic acid formed from

A

Methanol ingestion

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15
Q

Which acid must be buffered before being excreted by kidneys

A

Nonvolatile acids

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16
Q

Which compensation takes longer, renal or respiratory

A

Renal, respiratory compensation is very fast

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17
Q

Major buffers of EXTRACELLUAR fluid are

A

Bicarbonate and phosphate

Used to maintain the pH stable before they are excreted in urine

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18
Q

Bicarbonate buffering

A

H2O + CO2 H2CO3 HCO3- + H+

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19
Q

Phosphate buffering

A

H2PO4 < –> HPO4^2- + H+

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20
Q

Major buffers of INTRACELLULAR fluid are

A

Organic phosphates and proteins

Hb most significant

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21
Q

Henderson-Hasselbacch equation used to

A

Calculate pH of arterial blood pressure
pH = pK + log [A-]/[HA]
pH = 6.1 + log[HCO3-]/(0.3 x pCO2)

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22
Q

In reabsorption of filtered HCO3-, how much of it is reabsorbed

A

99.9%

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23
Q

Why is HCO3- rebasorbed

A

To ensure that the major EXTRACELLULAR BUFFER is conserved

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24
Q

Reabsorption of HCO3- in Proximal Tubule

A

80%

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25
Q

Reabsorption of HCO3- in Thick Ascending Limb in loop of Henle

A

10%

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26
Q

Reabsorption of HCO3- in A-Intercalated Cells of distal nephron

A

9.9%

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27
Q

Calculation of reabsorption

A

Glomerular filtration rate x Plasma [HCO3-] x Excretion rate of HCO3-

28
Q

Reabsorption rate of HCO3- with numbers:

A

180L/d x 24mEq/L x 2mEq/d = 4318mEq/d

29
Q

Meaning of reabsorption

A

Fluids going back to the vessels

30
Q

Meaning of secretion

A

Fluids going into the renal tube

31
Q

In the reabsorption of HCO3-, there is also reabsorption of

A

Na+

32
Q

Is there NET SECRETION of H+

A

NO

33
Q

NBC1:

A

Electronic Na+/HCO3- cotransporter 1

34
Q

AE1:

A

Anion exchanger 1 (Cl-)

35
Q

NHE-3:

A

Na+/H+ antitransporter 3

36
Q

EFFECT OF FILTERED LOAD When does HCO3- absorption mechanism become saturated

A

When [plasma] > 40mEq/L –> metabolic alkalosis

37
Q

When reabsorption mechanism saturated due to metabolic alkalosis,

A

Non-reabsorbed HCO3- is excreted in urine so that [blood] decreases to normal

38
Q

EFFECT EXTRACELLULAR VOLUME, a decrease in ECV will activate the

A

Renin-angiotensin II-aldosterone

39
Q

What stimulated the renin-angiotensin II-aldosterone

A

Na+/H+ exchange (NHE-3), stimulated HCO3- reabsorption

40
Q

An increase in HCO3- reabsorption will cause

A

Contraction alkalosis from an increased pH in blood (more alkaline)

41
Q

EFFECT OF PCO2

A

Increased pCO2 = Increased HCO3- reabsorption (bc CO2 is considered an acid, we want to lower the pH)
Decreased pCO2 = Decreased HCO3- reabsorption (we want to increase the pH)

42
Q

Why dont we want direct elimination of H+ in urine

A

Bc it would make the urine pH=1.3

43
Q

Which is the most important buffer due to increased concentration in urine

A

Phosphate

44
Q

How much phosphate reabsorbed

A

85%

45
Q

How much phosphate left to be excretes as titrable acid

A

15%

46
Q

1st mechanism for H+ secretion is

A

H+ATPase stimulated by aldosterone

47
Q

2nd mechanism for H+ secretion

A

H+/K+ATPase

48
Q

Amount of H+ excreted depends on

A

Amount of acid buffer available

49
Q

Blood vs urine pH

A 
Blood = 7.4
Urine = 4.4
50
Q

When does H+ excretion stop

A

When pH of urine reached 4.4

51
Q

Other mechanism used asides from HPO4-

A

Excretion of H+ as NH4+ + HCO3-

52
Q

Why is there another mechanism asides from phosphate

A

Because if not, excretion would be limited by the amount of phosphate in urine

53
Q

Segments in nephron participating in H+ excretion as NH4+

A

Proximal tubule
Thick ascending limb
A-intercalated cells

54
Q

Proximal tubule function in H+ excretion as NH4+

A

Proximal tubule, NH4+ secreted by Na+ - H+ exchange

55
Q

Thick ascending limb function H+ excretion as NH4+

A

Thick ascending limb, NH4+ secretion by proximal tubule is REABSORBED

56
Q

A-intercalated cells function in H+ excretion as NH4+

A

A-intercalated cells, NH3+ and H+ secreted into lumen

57
Q

In proximal tubule, which Aa produces HCO3-

A

Glutamine

58
Q

Glutamine in proximal tubule separates into

A

a-ketoglutarate

NH4+

59
Q

In thick ascending limb, what happens with NH4+

A

It is reabsorbed, participates in counter-current multiplication

60
Q

In a-intercalated cells, NH3

A

Can diffuse so it goes directly to lumen from blood

61
Q

For each H+ secreted, how many HCO3-

A

One new HCO3- syntehtised and reabsorbed

62
Q

Effect of urinary pH on excretion of NH4+

A

pH decreases = increase in NH4 buffer = less NH3

A decreased NH3 will cause a greater gradient for NH3 diffusion from interstitium to lumen

63
Q

Effect of acidosis on NH3 synthesis

A

NH3 synthesis depends on how much H+ to be excreted

64
Q

In chronic acidosis, there is an

A

Increased NH3+ synthesis of proximal tubule

65
Q

Why does hyperkalemia inhibit NH3 synthesis

A

K+ will move into cell, causing H+ out of cell

Causing an increase in intracellular pH (more alkaline)

RENAL (9 decks)

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