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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
Reabsorption of HCO3- in Thick Ascending Limb in loop of Henle
10%
26
Reabsorption of HCO3- in A-Intercalated Cells of distal nephron
9.9%
27
Calculation of reabsorption
Glomerular filtration rate x Plasma [HCO3-] x Excretion rate of HCO3-
28
Reabsorption rate of HCO3- with numbers:
180L/d x 24mEq/L x 2mEq/d = 4318mEq/d
29
Meaning of reabsorption
Fluids going back to the vessels
30
Meaning of secretion
Fluids going into the renal tube
31
In the reabsorption of HCO3-, there is also reabsorption of
Na+
32
Is there NET SECRETION of H+
NO
33
NBC1:
Electronic Na+/HCO3- cotransporter 1
34
AE1:
Anion exchanger 1 (Cl-)
35
NHE-3:
Na+/H+ antitransporter 3
36
EFFECT OF FILTERED LOAD When does HCO3- absorption mechanism become saturated
When [plasma] > 40mEq/L --> metabolic alkalosis
37
When reabsorption mechanism saturated due to metabolic alkalosis,
Non-reabsorbed HCO3- is excreted in urine so that [blood] decreases to normal
38
EFFECT EXTRACELLULAR VOLUME, a decrease in ECV will activate the
Renin-angiotensin II-aldosterone
39
What stimulated the renin-angiotensin II-aldosterone
Na+/H+ exchange (NHE-3), stimulated HCO3- reabsorption
40
An increase in HCO3- reabsorption will cause
Contraction alkalosis from an increased pH in blood (more alkaline)
41
EFFECT OF PCO2
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
Why dont we want direct elimination of H+ in urine
Bc it would make the urine pH=1.3
43
Which is the most important buffer due to increased concentration in urine
Phosphate
44
How much phosphate reabsorbed
85%
45
How much phosphate left to be excretes as titrable acid
15%
46
1st mechanism for H+ secretion is
H+ATPase stimulated by aldosterone
47
2nd mechanism for H+ secretion
H+/K+ATPase
48
Amount of H+ excreted depends on
Amount of acid buffer available
49
Blood vs urine pH
``` Blood = 7.4 Urine = 4.4 ```
50
When does H+ excretion stop
When pH of urine reached 4.4
51
Other mechanism used asides from HPO4-
Excretion of H+ as NH4+ + HCO3-
52
Why is there another mechanism asides from phosphate
Because if not, excretion would be limited by the amount of phosphate in urine
53
Segments in nephron participating in H+ excretion as NH4+
Proximal tubule Thick ascending limb A-intercalated cells
54
Proximal tubule function in H+ excretion as NH4+
Proximal tubule, NH4+ secreted by Na+ - H+ exchange
55
Thick ascending limb function H+ excretion as NH4+
Thick ascending limb, NH4+ secretion by proximal tubule is REABSORBED
56
A-intercalated cells function in H+ excretion as NH4+
A-intercalated cells, NH3+ and H+ secreted into lumen
57
In proximal tubule, which Aa produces HCO3-
Glutamine
58
Glutamine in proximal tubule separates into
a-ketoglutarate | NH4+
59
In thick ascending limb, what happens with NH4+
It is reabsorbed, participates in counter-current multiplication
60
In a-intercalated cells, NH3
Can diffuse so it goes directly to lumen from blood
61
For each H+ secreted, how many HCO3-
One new HCO3- syntehtised and reabsorbed
62
Effect of urinary pH on excretion of NH4+
pH decreases = increase in NH4 buffer = less NH3 | A decreased NH3 will cause a greater gradient for NH3 diffusion from interstitium to lumen
63
Effect of acidosis on NH3 synthesis
NH3 synthesis depends on how much H+ to be excreted
64
In chronic acidosis, there is an
Increased NH3+ synthesis of proximal tubule
65
Why does hyperkalemia inhibit NH3 synthesis
K+ will move into cell, causing H+ out of cell | Causing an increase in intracellular pH (more alkaline)

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