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Physiology Exam 1(Lauren) > Acid Base Physiology > Flashcards

Acid Base Physiology Flashcards

1
Q

What are the 3 main components that regulate H+ in the body?

A

Buffers- bicarbonate, proteins, phosphates, etc

Respiratory compensation- alters CO2 leverls

Renal compensation-alters HCO3- levels

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2
Q

Can buffers correct pH?

A

No, they can “blunt” changes to pH

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3
Q

Which faster: respiratory compensation or metabolic compensation

A

Respiratory

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4
Q

What is the normal plasma concentration of H+

A

40nEq/L

4x10-8 moles

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5
Q

What is the normal blood pH range?

A

7.35-7.45

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6
Q

What is normal blood pH?

A

7.4

MUST memorize

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7
Q

What is “volatile” acid?

A

CO2 that is produced in the lungs.

THIS IS THE ONLY VOLATILE ACID IN OUR BODY IF YOU SEE IT ON AN EXAM IT’S CO2

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8
Q

What are non-volatile or fixed acids?

A

Acids that arise from normal and abnormal processes:

  • degradation of amino acids
  • lactic acid
  • ketones in DKA

Etc

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9
Q

We produce ______mEq/day of fixed acid

A

50mEq

Due to gluconeogenic utilization of AA’s in the liver,

Sulfuric acid from methionine etc

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10
Q

What is the Henderson-hasselbalch equation?

A

pH=pK + log [A-]/[HA]

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11
Q

When [A-]=[HA], then what is the pH

A

pH=pK

Think about it if [a]/[ha] =1, and you take the log of 1, you get 0

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12
Q

What are strong acids?

A

Have lower affinities for hydrogen ions which easily dissociate from the conjugate base and have LOW pKs

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13
Q

What are weak acids?

A

Acids that have higher affinities for H+ and do not dissociate as easily from the conjugate base. Have HIGHER pKs

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14
Q

Where are buffers located?

A

ECF, ICF, bone

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15
Q

What is our first line defense against pH changes?

A

Buffers

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16
Q

What is the most important buffer in the ECF?

A

Bicarbonate

Due to its high concentration

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17
Q

What 2 things contribute to a buffer’s effectiveness?

A

Its concentration

Its pK

18
Q

Buffers consist of a pair of:

A

Acid and conjugate base

HA/A-

19
Q

At low pHs, which will be higher: [HA] or [A-]

A

[HA]

20
Q

At high pHs, which will be higher: [HA] or [A-]

A

[A-]

21
Q

At what pHs are buffers most effective

A

+/- one pH unit from their pK

22
Q

What is the acid/conjugate base pair for the bicarbonate buffer system?

A

HCO3-/H2CO3

23
Q

What is the acid/conjugate base pair for the phosphate buffer system?

A

HPO42-/H2PO4-

24
Q

At a pH of 7.4, which will be a better buffer:

Phosphate: pK 6.8

Bicarbonate: pK 6.1

A

Technically phosphate would be a better buffer since its pK is closer to 7.4, but bicarbonate is more important in the blood

25
Q

What are the 4 buffers in the blood?

A
  1. Bicarbonate (53% of total buffering capacity)
  2. Hemoglobin (35%)
  3. Proteins (7%)
  4. Phosphate (5%)
26
Q

How does hemoglobin act as a buffer?

A

Imidaizole groups on histidine and α amino groups are the primary buffer sites on ALL proteins

27
Q

Why is phosphate unimportant in blood?

A

It is at a low concentration

28
Q

What are the 3 intracellular buffers?

A

Proteins- high conc, pK close to 7.4

Phosphate-same as proteins

Bicarb (less important because concentration is low)

29
Q

How does bone act like an intracellular buffer?

A

It takes up H+ in exchange for Na+ and K+

May account for a significant amount of buffering capacity during acute acid load

30
Q

What is the normal range for pCO2?

A

35-45

31
Q

What is the normal range for HCO3-?

A

22-26

32
Q

Why do we use CO2 to calculate pH if the the equation uses log[A-]/[HA]

A

Because CO2 drives the formation of H2CO3

                     [HCO3] pH= pK + log \_\_\_\_\_\_\_\_\_\_\_\_
                      .03(CO2)

Can you see how that is [A-]/[HA]

33
Q

Lungs and kidneys regulate CO2 and HCO3 so that the [HCO3]/[CO2] remains near________

A

20

34
Q

Can the kidneys AND the lungs compensate for metabolic disturbances (changes in [HCO3])?

A

Yes, but NOT if the kidneys caused the metabolic defect in the first place

35
Q

What organ must compensate for respiratory disturbances?

A

Kidneys only

Compensation takes days

36
Q

If you go into metabolic acidosis by eating acid or through the formation of metabolic acids, what will happen?

A
  1. Plasma HCO3 decreases when you eat acid(causes the acidosis)
  2. Respiratory system responds by increasing ventilation to expel CO2
  3. Kidneys synthesize new HCO3
37
Q

What can cause respiratory acidosis?

A

Decreased ventilation (drug overdose, airway obstruction)

38
Q

How will the kidneys respond to respiratory acidosis?

A

They will synthesize new HCO3 and excrete H+

39
Q

What can cause respiratory alkalosis?

A

Hyperventilation (stress, high altitude, etc)

40
Q

How will the kidneys respond to respiratory alkalosis?

A

They will excrete HCO3 causing the urine to become alkaline, while the blood pH will decrease

41
Q

How do you calculate pH using HCO3 and PCO2?

A

[HCO3]
pH= pK + log ___________
(0.3)(PCO2)

Physiology Exam 1(Lauren) (12 decks)

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