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Physiology > Integrative Physiology III Regulation of Acid Base Balance > Flashcards

Integrative Physiology III Regulation of Acid Base Balance Flashcards

1
Q

what is the pH of arterial blood, venous blood and interstitial fluid

A

-arterial: 7.4
- venous: 7.35
- interstitial: 7.35

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2
Q

why is pH in venous blood and intersitital fluid lower

A

higher concentration of carbon dioxide due to carbonic anhydrase reaction so more H+

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3
Q

what is the normal ECF [H+]

A

0.00004 mEq/L

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4
Q

what are the sources for hydrogen ion gain

A
  • generation of H+ from CO2
  • production of nonvolatile acids from the metabolism of proteins and other organic molecules
  • gain of H+ due to loss of HCO3- in diarrhea or other nongastric GI fluids
  • gain of H+ due to loss of HCO3- in the urine
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5
Q

what are the sources of H+ loss

A

-utilization of H+ in the metabolism of various organic anions
- loss of H+ in vomit
- loss of H+ in urine
- hyperventilation

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6
Q

how much do fixed acids add to acid production a day

A

80 mEq/day

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7
Q

what are sources of fixed acid/non volatile production

A

-protein catabolism: sulfuric acid and HCL
- phospholipid catabolism: phosphoric acid
-exercsie, hypoxia: lactic acid
- post absorptive state, DM: acetoacetic acid and beta hydroxy butyric acids
- nucleoprotein metabolism: uric acid

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8
Q

how are fixed acids filtered

A

all excreted by the kidneys

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9
Q

what are the three primary systems that regulate the [H+] in body fluids

A

-chemical
-respiratory
- kidneys

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10
Q

describe how chemically [H+] is regulated

A

-acid base buffer systems
-instantaneous
-does not add or remove H+ but keeps it tied up until balance can be re established

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11
Q

what are the buffers of ECF and which is more powerful

A

-bicarbonate buffer system- more powerful
- phosphate buffer system

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12
Q

what are CO2 and HCO3- regulated by

A

respiratory and renal systems

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13
Q

what is the phosphate buffer system

A

H2PO4- -> H+ + HPO4(2-)

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14
Q

what is the phosphate buffer system important for

A

buffering renal tubular fluids and ICF

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15
Q

where does 60-70% of total chemical buffering occur

A

inside the cells

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16
Q

how can H+ enter cells

A

-CO2
- produced: lactic, acetoacetic, beta hydroxyl butyric acid
- H+/K+ exchange

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17
Q

what are the intracellular buffers

A

-proteins (Hb and deoxyHb)
- organic phosphates such as ATP, ADP, AMP, glucose-1-PO4, and 2,3 BPG

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18
Q

how does the respiratory system regulate [H+]

A

-regulates removal of CO2
-changes alveolar ventilation
- occurs fast: seconds to minutes

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19
Q

resting normal human produces _____ of CO2 per minute

A

200mL

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20
Q

what 3 processes facilitate CO2 transport

A

-10% dissolved in plasma
- 25% binds to amino groups in Hb
- 65% carbonic acid in RBCs

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21
Q

what does alveolar exchange do

A

removes CO2

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22
Q

what do disorders of the respiratory system lead to

A

respiratory alkalosis or acidosis

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23
Q

what can changes in alveolar ventilation function to restroe

A

pH following acid base disturbances

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24
Q

how do the kidneys function to regulate [H+]

A

-excrete an acidic or alkaline urine
- slow: hours to days
-most powerful of the acid/base regulatory systems

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25
Q

how do kidneys regulate pH

A

by altering plasma [HCO3-]
-secrete H+
-reabsorb, produce, or excrete HCO3-

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26
Q

where does most HCO3- absorption and H+ secretion occur

A

proximal tubule

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27
Q

for each HCO3- reabsorbed _____ must be secreted

A

a H+

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28
Q

how is H+ secreted

A

by secondary active transport

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29
Q

where does secondary active secretion of H+ occur

A

PT, TAL, and early distal tubule

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30
Q

_____ of filtered HCO3- reabsorbed and requires _____ of H+ to be secreted

A

95%; 4000 mEg

31
Q

where is HCO3- titrated with H+

A

in tubule lumen

32
Q

what is the rate of tubule H+ secretion

A

4400 mEq/day

33
Q

what is the renal load of HCO3- per day

A

4320 mEq/day

34
Q

in alkalosis what is the relationship with HCO3- load and H+ secretion

A

HCO3- load > H+ secretion and excess HCO3- will be excreted

35
Q

in acidosis what is the relationship between H+ secretion and HCO3- load

A

H+ secretion > HCO3- load and excess H+ is secreted

36
Q

what is excess H+ excretion a function of

A

late DT and CD

37
Q

what percentage of H+ secretion is late DT and CD responsible for

A

only 5% but its enough to create maximally acidified urine

38
Q

what systems are used for excess H+ excretion

A

Phosphate and glutamine/NH4+

39
Q

what does abnormal H+ production induce

A

renal compensation

40
Q

where does primary active secretion of H+ occur

A

in the alpha intercalated cells of late distal and collecting tubules

41
Q

where does the phosphate buffer system act in the nephron

A

PT, TAL, and early distal tubule

42
Q

when does the phosphate buffer system come into play

A

when secreted H+ exceeds filtered load of HCO3-, H+ can bind to phosphate buffer system

43
Q

what is the result of H+ combining with a buffer other than HCO3-

A

new HCO3- is added to the ECF

44
Q

what happens to most filtered phosphate

A

it gets reabsorbed so theres only a small amount available to interact with H+ in filtrate

45
Q

what is the maximum amount of excess H+ that can be buffered and excreted

A

500 mEq/day

46
Q

describe the ammonia buffer system

A

-NH3 produced from protein metabolism in liver, converted into urea and glutamine
-in PT,TAL, and DT, NH4+ is added to filtrate following glutamine metabolism and represents acid secretion
- in CD, NH3 is secreted into lumen where it combines with H+ to form NH4+
-results in new HCO3- added to ECF

47
Q

what percent of acid excreted and new HCO3- added to ECF does the ammonia buffer system account for

A

50% of each

48
Q

H+ secretion by tubular epithelium is necessary for:

A

-HCO3- reabsorption
-addition of new HCO3- to ECF
- acid excretion
-rate of secretion must be carefully controlled to maintain acid-base homeostasis

49
Q

under normal conditions: acid secretion needs to be enough to:

A
  • reabsorb almost all filtered HCO3-
  • rid the body of non-volatile acids produced during metabolism
50
Q

why is acid secretion decreased during alkalosis

A

-not all filtered HCO3- is reabsorbed
- HCO3- is excreted
-No NH4+ or H2PO4-, no non-volatile acid excreted, no new HCO3- added

51
Q

why is acid secretion increased during acidosis

A
  • almost all filtered HCO3- is reabsorbed
  • NH4+ and H2PO4- generated, acid excreted, new HCO3- added
52
Q

what are the two most important stimuli that increase H+ secretion by tubules

A

-increase in Pco2 of ECF
- increase [H+]ECF

53
Q

what factors increase H+ secretion and HCO3- reabsorption

A

-increase in Pco2
- increase H+ and decrease HCO3-
- increase ANG II
- increase aldosterone
- hypokalemia
- alkalosis

54
Q

what factors decrease H+ secretion and HCO3- reabosrption

A

-decreased Pco2
- decreased H+ and increased HCO3-
- decreased ANG II
- decreased aldosterone
- hyperkalemia
- acidosis

55
Q

what are the types of acid-base disturbances

A
  • respiratory acidosis
  • metabolic acidosis
  • respiratory alkalosis
  • metabolic alkalosis
56
Q

what happens in respiratory acidosis

A
  • problems with ventilation or gas exchange: hypoventilation, PE, COPD
    -increased PCO2
57
Q

what is the compensation for respiratory acidosis

A
  • buffer of body
    -renal compensation
    -reabsorb all filtered HCO3-
    -secrete excess H+ and add new HCO3- to ECF ( increased glutamine metabolism and NH4+ excretion)
58
Q

what is metabolic acidosis

A
  • a decrease in pH not associated with an increase in CO2 levels
59
Q

what happens in metabolic acidosis

A
  • failure of kidney to excrete metabolic wastes (renal failure or addisons)
  • formation of excess amounts of metabolic acid (ketoacidosis)
  • increased input of metabolic acids
  • loss of base from body
60
Q

what is the compensation for metabolic acidosis

A

-buffer of body
-renal compensation: reabsorb all filtered HCO3-, secrete excess H+ and add new HCO3- to ECF
-respiratory compensation: compensatory increase in alveolar ventilation in response to metabolic acid

61
Q

what happens in respiratory alkalosis

A
  • excessive ventilation leading to decreased PCO2
    -rare
62
Q

what is the compensation for respiratory alkalosis

A

-buffer of body
-renal compensation: increased HCO3- excretion, decreased H+ excretion

63
Q

what is metabolic alkalosis

A

-an increase in pH not associated with a decrease in CO2 levels

64
Q

what causes metabolic alkalosis

A
  • diuretics
    -excess aldosterone
    -excessive vomiting
  • ingestion of alkaline drugs
65
Q

what is the compensation for metabolic alkalosis

A
  • buffer of body
    -renal compensation: increased HCO3- excretion, decreased H+ excretion
  • respiratory compensation: compensatory decrease in alveolar ventilation in response to metabolic alkalosis
66
Q

what is the primary abnormality in respiratory alkalosis and acidosis

A

CO2 change

67
Q

what is the primary abnormality in metabolic acidosis and alkalosis

A

HCO3- change

68
Q

what are the levels of H+, HCO3-, and CO2 in respiratory acidosis

A

-H+: high
- HCO3-: high
- CO2: high

69
Q

what are the levels of H+, HCO3-, and CO2 in respiratory alkalosis

A
  • H+: low
  • HCO3-: low
    -CO2: low
70
Q

what are the levels of H+, HCO3-, and CO2 in metabolic acidosis

A

-H+: high
- HCO3-: low
- CO2: low

71
Q

what are the levels of H+, HCO3-, and CO2 in metabolic alkalosis

A

-H+: low
- HCO3-: high
- CO2: high

72
Q

what is the normal concentration of HCO3-

A

24 mEq/L

73
Q

what is the normal concentration of PCO2

A

40 mmHg

Physiology (41 decks)

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