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Hum Physiology II > Lect 9 > Flashcards

Lect 9 Flashcards

1
Q

What are the three main components of the homeostatic mechanisms that regulate [H+] in the body

A
  • buffers: bicarb, phosphates, etc
  • respiratory compensation: alters CO2 levels
  • renal compensation: alters HCO3- levels
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2
Q

what is the plasma concentration of H+

A

40 nEq/L

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3
Q

equation for pH

A

pH = -log[H+]

  • 10 fold increase in [H+] = 1 unit change in pH
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4
Q

normal blood pH level

A
  • 7.4
  • normal range: 7.37-7.42
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5
Q

what is volatile acid

A
  • source of H+ that is produced from respiratory CO2 and handled by the lungs
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6
Q

what are some examples of non-volatile or fixed acid (50 mEq/day)

A
  • degradation of certain amino acids
    • sulfuric acid from methionin and cysteine
    • phosphoric acid from phospholipid
  • exercise (lactate)
  • diabetic ketosis
  • ingestion of acids

**acid load that kidney must eliminate

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7
Q

differentiate between acid and base in terms of donor and acceptor

A
  • acid: H+ donor
  • base: H+ acceptor
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8
Q

in HA <-> H+ + A-, which is the conjugate base

A
  • A-
  • The conjugate base of an acid is formed when the acid donates a proton
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9
Q

with this equation in mind HA <-> H+ + A-, how can it be rearranged to make a constant

A

K = [A-][H+] / [HA]

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10
Q

what is the henderson-hasselbalch equation

A

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

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11
Q

with this equation in mind pH = pK + log ([A-] / [HA]), when does pH = pK?

A

when [A-] = [HA]

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12
Q

describe strong acids. do they have a lower or higher pK?

A
  • lower affinities for hydrogen ions -> will dissociate easily from conjugate base
  • lower pKs
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13
Q

describe weak acids. do they have a lower or higher pK?

A
  • have higher affinities for hydrogen ions -> will not dissociate easily from conjugate base
  • higher pKs
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14
Q

buffers are the first line of defense against pH changes. effectiveness of a buffer is proportional to?

A
  • its concentration
  • its pK
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15
Q

what is the most important buffer system in the ECF?

A
  • bicarbonate buffer system
    • due to high concetration and both CO2 and HCO3- are tightly regulated
  • CO2 + H2O <-> H2CO3 <-> H+ + HCO3-
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16
Q

what do buffers consist of

A

acid and conjugate base pairs

  • ex: HA/A-
17
Q

what are the most effective buffers in terms of pH

A
  • most effective buffering is +/- one pH unit from pK
18
Q

what are the acid/conjugate base pairs form bicarb and phosphate buffer systems

A
  • HCO3-/H2CO3
  • HPO42-/H2PO4-
19
Q

Bicarbonate accounts for 53% of total buffering capacity. Why is it effective

A
  • pK is low (6.1) but effective due to its concentration and because both the acid (H2CO3) and base (HCO3-) are regulated
20
Q

Hemoglobin accounts for 35% of total buffering capacity. What is the buffer?

A
  • Hb - + H+ <-> HHb
  • Imidazole groups on histidine and alpha amino groups are the primary buffer sites on all proteins
21
Q

What are the four buffers in blood

A
  1. bicarbonate
  2. hemoglobin
  3. proteins (7%): low conc.
  4. phosphate (5%): very important in urine
22
Q

what are the primary intracellular buffers?

A
  • proteins (pK close to 7.4)
  • phosphate
23
Q

how can bone act as a buffer

A
  • takes up H+ in exchange for Na+ and K+
  • helps during acute acid load
24
Q

what are the normal ranges for pH, PCO2, and HCO3-

A
  • pH = 7.4
  • PCO2 = 40 mmHg
  • HCO3- = 24 mEq/L
25
Q

what is the equation that determines pH (values inserted for HH equation)

A

pH = 6.1 + log [HCO3-] / (0.03 x PCO2)

26
Q

pH = 6.1 + log [HCO3-] / (0.03 x PCO2); decreased bicarbonate or increased PCO2 will give what state

A

acidosis

27
Q

pH = 6.1 + log [HCO3-] / (0.03 x PCO2); increased bicarbonate or decreased PCO2 will give what state

A

alkalosis

28
Q

buffers can’t return pH to normal, lungs and kidneys regulate CO2 and HCO3- respectively such that the ration of [HCO3-] to dissolved CO2 = X

A

20

29
Q

changes in [HCO3-] are considered metabolic or respiratory disturbances? What organs can compensate?

A
  • loss or gain of HCO3- = metabolic disturbance
  • compensated for by both kidneys and lungs
30
Q

which is quicker, metabolic or respiratory compensation?

A

respiratory

31
Q

changes in [CO2] are considered metabolic or respiratory disturbances? What organs can compensate?

A
  • respiratory disturbances
  • must be compensated for by the kidney
32
Q

what happens in metabolic acidosis

A
  1. plasma HCO3- decreases
  2. respiratory system responds by increasing ventilation to expel CO2; kidneys synthesize new HCO3-
33
Q

what happens in metabolic alkalosis

A
  1. plasma HCO3- increases
  2. respiratory system responds by reducing ventilation to retain CO2; kidneys excretes excess HCO3-
34
Q

what happens in respiratory acidosis

A
  1. plasma PCO2 increases
    • caused by decreased ventilation (drug overdose, airway obstruction)
  2. kidneys will synthesize new HCO3- and excrete H+ in the urine to raise blood pH
35
Q

what happens in respiratory alkalosis

A
  1. plasma PCO2 decreases
    • caused by hyperventilation (stress, high altitude)
  2. ​kidneys will excrete HCO3- causing urine to become alkaline; blood HCO3- and pH will decrease

Hum Physiology II (12 decks)

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