Acid-Base balance I Flashcards

1
Q

What is pH?

A

pH = log 1/H

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2
Q

What is the pH of arterial blood?

A

7.45

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3
Q

What is the pH of venous blood?

A

7.35

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4
Q

What is the pH of the ECF controlled close to?

A

7.4

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5
Q

What can acidosis do?

A

lead to depression of CNS

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6
Q

What can alkalosis do?

A

over-excitability of peripheral NS or later the CNS

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7
Q

What does H influence?

A

enzyme activity and K levels in the body

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8
Q

How is H continually added to the body fluids?

A

metabolic activity
carbonic acid formation
inorganic acids from breaking down nutrients
organic acids from metabolism

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9
Q

What is the dissociation constant for acids and bases?

A

K = [H][A]/HA

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10
Q

What is pK equal to?

A

pK=-logK

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11
Q

What is the henderson-hasselbach equation?

A

H = K x HA/A
OR
pH = pK + log [A]/[HA]

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12
Q

What are some physiological buffers?

A

HCO3-CO2

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13
Q

Why is the HCO3-CO2 buffer so important?

A

HCO3 is controlled by kidneys, PCO2 is controlled by lungs

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14
Q

How does the HCO3-CO2 buffer influence physiological pH?

A

pH = pK + log [HCO3]/pCO2 x 0.03 solubility coefficient
Normal conditions HCO3 = 24 mmol, pCO2 is 40 mmHg
pH = 6.1 + log 24/40.0.03 = 7.4

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15
Q

What is the role of the kidney in control of HCO3?

A

variable reabsorption of filtered HCO3

Kidneys can add new HCO3 to the blood

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16
Q

What does the kidneys control of HCO3 depend upon?

A

H secretion into the tubule

17
Q

How much HCO3 is filtered per day?

A

4320 mmol/day

18
Q

How does HCO3 get back into the interstitial fluid?

A

Doesn’t do it as an ion
takes H from NHE -> H2CO3 which is converted to CO2 which diffuses into epithelial cell where converted back to HCO3 which goes to interstitial fluid via Na/HCO3 cotransporter

19
Q

How does the kidney form new HCO3 when HCO3 is low?

A

secreted H binds with next most plentiful buffer in filtrate - phosphate

20
Q

How does phosphate act as a buffer?

A

binds H and HPO4 to make H2PO4 which is an acid that is excreted so there is a net gain of HCO3

21
Q

What is titratable acid?

A

the amount of H excreted as H2PO4 can be measured

22
Q

What is the maximum amount of titratable acid that can be excreted per day?

A

40mmol/day

23
Q

What happens if 40mmol/day is added as titratable acid then how much HCO3 is gained by the circulation?

A

40mmol/day

24
Q

How does ammonia act as a tubular buffer?

A

NH3 binds H to make ammonium ion that is excreted causing net gain of HCO3

25
How is ammonia secreted into the tubule?
glutamine from the liver -> glutaminase -> NH3 in tubule
26
What is the usual excretion of NH4?
20mmol/day
27
What may happen in acidosis?
NH4 excretion increases to 5-600mmol/day
28
What are the three actions of H?
drives HCO3 reabsorption - 4300mmol/day Forms acid phosphate 20 mmol/day Forms ammonium ion - 40 mmol/day
29
What is the total H secretion per day?
sum of all the HCO3 reabsorption and TA and NH4 excretion - 4360mmol/day
30
What is the total H excretion per day?
sum of Ta and NH4 excretion - 60 mmol/day
31
What is the total amount of new HCO3 generated a day?
60mmol/day