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Bioscience II > Acid-Base Balance > Flashcards

Acid-Base Balance Flashcards

1
Q

What is normal pH?

A

7.35-7.45

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2
Q

What defines acidosis?

A

pH

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3
Q

What defines alkalosis?

A

pH> 7.45

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4
Q

What occurs when [H+] is too high?

A

H+ diffuses into cells and K+ moves out resulting in hyperkalemia which can depress excitability

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5
Q

What happens when [H+] is too low?

A

H+ will diffuse out of the cell and K+ will move into the cell causing hypokalemia making the cells hyper excitable

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6
Q

What is an acid?

A

a hydrogen ion donor

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7
Q

example of a strong acid

A

HCl

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8
Q

example of a weak acid

A

HAc

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9
Q

What is a base?

A

hydrogen ion accepter; it takes hydrogen ions out of solution

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10
Q

What are the 3 systems that defend pH homeostasis?

A

chemical buffers
the lungs
the kidneys

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11
Q

How does a buffer work?

A

minimizes pH changes in the presence of an acid or alkaline load; it does this very rapidly and is effective only when there is a disturbance

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12
Q

How do the lungs help with regulating plasma pH?

A

they have the ability to control CO2 very rapidly

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13
Q

How do the kidneys help with regulating plasma pH?

A

due to their ability to variably reabsorb HCO3– and secrete H+

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14
Q

Where does most of bicarbonate reabsorption occur?

A

in the proximal nephron segments

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15
Q

What do we depend on to reabsorb bicarbonate?

A

carbonic anhydrase

if this is inhibited in renal cells, then HCO3- reabsorption stops and we become acidotic

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16
Q

What happens if a large quantity of H+ is added to the blood?

A

insufficient HCO3- absorption

excess H+ ions would need to be removed to be excreted in the urine

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17
Q

What happens if carbonic anhydrase is inhibited?

A

H+ secretion slows down and we become acidotic

18
Q

How is the urine never less than 5 pH?

A

it has titratable acids in the tubular fluid
also tubular cells synthesize ammonia (NH3) which is a strong base and forms ammonium (NH4+) which is excreted in the urine

19
Q

What are the 2 factors related to effectiveness of a buffer system?

A

-the conc. of the buffers
higher conc.=greater capacity to minimize pH changes
-the Ka of the system
goal is to have the pKa near the desired pH target

20
Q

What is the pKa of an ideal buffer system?

A

about 7.4

21
Q

list the buffers in ECF

A

bicarbonate
phosphate
amino acids
hemoglobin

22
Q

what does the ratio of acid/base need to be near for the pH to be normal?

A

the ratio needs to be near 20 for a pH to be normal (7.4)

23
Q

What is metabolic acidosis?

A

when the pH is too low because [HCO3-] is too low

24
Q

What can cause metabolic acidosis?

A

due to addition of fixed acids (lactic acid, ketoacids) or loss of HCO3 (uncontrolled diabetes, starvation, low carb diet, exercise, hypoxia)
- HCO3– may be lost in GI secretions via diarrhea
decreased ability of the kidney to reabsorb bicarbonate or secrete H+ (kidney disease)

25
Q

How do we try to compensate during metabolic acidosis?

A

buffering by base component of system!
- hyperventilation to decrease PCO2 (rapid)!
- kidneys will reabsorb all filtered HCO3– and synthesize new HCO3– (secrete
H+) (takes hours to days)!
- the result is that hyperventilation moves the acid/base ratio closer to 20 and,
over days, the kidneys will restore the HCO3– used to buffer H+

26
Q

signs and symptoms of metabolic acidosis

A 
hyperventilation!
• depression of nervous system activity!
- weakness!
- fatigue!
- confusion!
- motor impairments!
- headache!
- decrease in bone mineral density (in chronic acidosis)
27
Q

What is metabolic alkalosis?

A

pH is too high because HCO3- is too high

28
Q

What are the responses to metabolic alkalosis?

A

buffering by acid component of system!
- hypoventilation to increase PCO2 (rapid)!
- kidneys will stop synthesizing new HCO3– (secrete H+) and fail to reabsorb
all the filtered HCO3–!
• bicarb will be excreted in urine, creating an alkaline urine with pH up to 9.0!
- the result is that hypoventilation moves the acid/base ratio closer to 20 and,
over days, the kidneys will reduce the HCO3– levels back to normal!

29
Q

What causes metabolic alkalosis?

A

chronic vomiting
hypokalemia (pulls K+ out of cells)
volume depletion

30
Q

What are signs and symptoms of metabolic alkalosis?

A

hypoventilation

excitation of NS- seizures

31
Q

What is respiratory acidosis?

A

pH is too low because PCO2 is too high

32
Q

What causes respiratory acidosis?

A

decrease in alveolar ventilation
lung disease (obstructive or restrictive)
depressed respiratory centers after head trauma
chest abnormalities or muscle weakness

33
Q

signs and symptoms of respiratory acidosis?

A

SOB
wheezing
headache
blurred vision

34
Q

What is respiratory alkalosis?

A

pH is too high because PCO2 is too low; not as common

35
Q

What is the body’s response to respiratory alkalosis?

A

buffers and respiratory system can not help out
the kidneys do most of the work by decreasing HCO3-
therefore acid/base ratio is moved closer to 20 and the pH is lowered

36
Q

what causes respiratory alkalosis?

A

hyperventilation due to panic attacks, fever or altitude

37
Q

signs and symptoms of respiratory alkalosis?

A

hyperexcitability of CNS- seizures

38
Q

What does a positive value for base excess indicate?

A

alkalosis

39
Q

What does a negative value for base excess indicate?

A

acidosis

40
Q

If a pH sample was reported as 7.47 what would this most likely mean?

A

that the hydrogen ion concentration was less than normal

41
Q

in a condition of respiratory acidosis, the HCO3-/CO2 ratio is what?

A

It is too low because PCO2 is too high

42
Q

A patient is in a state of metabolic alkalosis. Which condition in the patient’s chart is most likely to contribute to this acid-base disturbance?

A

excessive vomiting

Bioscience II (10 decks)

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