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urinary system > Acid base regulation > Flashcards

Acid base regulation Flashcards

1
Q

effect, and body’s response to hyperventilation

A

CO2 lost - increase in pH - resp alkalosis - compensatory change in renal func (H+ increase, HCO3- loss) - pH reduced ie restored

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2
Q

effect, and body’s response to hypoventilation

A

CO2 retention - increase pH - resp acidosis - comp change in renal function - HCO3- gain, H+ loss - increae in pH - pH restored

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3
Q

effect, and body’s response to change in renal func = HCO3- loss and H+ gain

A

decrease pH - metabolic acidosis - comp change in lung func - increase ventilation - CO2 blown off - increase pH

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4
Q

effect, and body’s response to change in renal func = HCO3- gain and H+ loss

A

pH increase - met alkalosis - change in lung func - hypovent - co2 retention - increase pH

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5
Q

what type of compensation - met/resp - is faster

A

resp

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6
Q

what is the normal pH

A

7.35-7.45

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7
Q

where does the acid come from in the body

A

13000mmols/d volatile acid excreted by lungs = 99%

100mmols/d excreted by the kidney = 1%

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8
Q

normal physiological H+ conc

A

40nmol/L

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9
Q

normal urine pH

A

there is no normal urine pH

it is the regulator to ensure the plasma pH stays constant

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10
Q

normal arterial bicarbonate

A

22-26mEq/l

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11
Q

describe bicarbonate

A

it is a high capacity chemical buffer
responds quickly to changes in metabolic acid
and can be produced from volatile resp acid

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12
Q

bicarbonate reabsorption

A 
reabsorbed at different points along the nephron 
- 80% in PCT 
10% ascending limb 
6% DCT 
4% collecting duct
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13
Q

why is all of the bicarbonate reabsorbed

A

it is a useful buffering system in the intracellular and extracellular environment

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14
Q

what is the Henderson-hasselbach eqn

A

pH = pKa + log10 [HCO3-]/[CO2]

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15
Q

constant value for pKa

A

6.1

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16
Q

normal value of HCO3- used in Henderson-hasselbach eqn

A

24mmol/L

17
Q

normal [CO2}

A

1.2mmol/L

18
Q

effect of changing [co2]

A

inverse effect on pH

19
Q

effect of changing [HCO3-]

A

direct effect on pH

20
Q

what is the davenport diagram

A

a graphical representation of the association between pH, bicarbonate and CO2 in blood

21
Q

describe the axis of the davenport diagram

A

Y - plasma bicarb conc mmol/L
bottom X - pH
top X - {H+] nmol/L
pCO2 (Kpa) is inside the graph and not a linear scale

22
Q

describe what is seen on the davenport diagram

A

normal pH is a vertivcal line
normal bicarb - horizontal line
normal zone - circle where these lines cross
met alkalosis - pH and bicarb increase (drive the alkalosis) - follow the CO2 line
met acidosis - H+ increase- pH decrease - follow the CO2 lines
acute resp alk - pH up, bicarb down, CO2 down
chronic resp alkalosis - same as acute but closer to the normal line - more time for compensation
acute resp acidosis - pH decrease, CO2 and bicarb increase
chronic resp acidosis - same but closer to normal

23
Q

why are resp disorders split into acute and chronic

A

rapid changes that quickly change the acid-base homeostasis/long slow

24
Q

what happens of the result is at the extremes of bircarb but normal pH in the davenport diagram

A

there is full compensation - pH is fine buyt there is a disturbance

25
Q

describe HCO3- reabsorption

A

NOT taken directly into cuboidal epithelia
CA convert it to CO2
CO2 diffuse into cell - hoghly diffusible
isoenzyme of carbonic anhydrase convert CO2 back to HCO3- and H+
H+ move back into filtrate - H+ ATPase or through Na/H+ antiporter (using the concentration gradient of Na for secondary AT)
bicarb into blood - HCO3-/cl- antiporter - cl reenter blood by Cl channel
- 3HCO3- and Na symporter (sodium bicarb cotransporter)
Na/K ATPase is there to regulate

26
Q

describe acid secreting cells of the collecting duct

A

alpha cells
CO2 enter cell from filtrate -> CA make H+ and bicarb - H+ enter filtrate through H/K ATPase - antiporter, H+ atpase, Na/H antiporter
bicarb enter vasa recta via - chloride bicarb exchanger

27
Q

describe bicarbonate secreting cells

A

beta cell

same process as the acid secreting cells - just the other way - ie bicarb into filtrate and h into vasa recta

28
Q

describe HCO3- generation by cells using glutamate

A

glutamate -> 2NH4+ and 2HCO3-
NH4+ antiported with na into filtrate
bicar enter vasa recta - ie is reabsorbed - chloride bicarb exchanger (AE1) and sodium bicarb cotransporter - 3HCO3- /Na
Na/K atpase - regulate

29
Q

describe HCO3- generation in cell using HPO4(2-)

A

CA make bicarb from H2O and CO2
bicarb reabsorbed through AE1 - cl/hco3- antiporter
cl- reabsorbed through cl channels

HPO4(2-) in filtrate combine with H+ (leaves cell through H+ ATPase) -> H+ + HPO4-

30
Q

compensation for resp acidosis

A

acute - intracellular buffering

chronic - HCO3- generation and increase NH4 excretion

31
Q

compensation for resp alkalosis

A

acute - buffer

chronic - reduced bicarb absorption and reduced ammonium excretion

32
Q

compensation for met alkalosis

A

hypovent - retain CO2

33
Q

compensation for met acidosis

A

hypervent - lose CO2

34
Q

how does increasing H+ counteract met alkalosis

A

the H+ bind to the excees bicarb - mopping it up

35
Q

limits of pH compatable with life

A

6.8-8 -> critically ill

36
Q

venous bicarb conc

A

22-29mmol/L

37
Q

why can phosphate be used in the filtrate to mop up H+ that are excreted

A

phosphate us freely filtered and 90% reabsorbed

38
Q

can met acidosis and alkalosis happen at same time

A

yes - the kidneys are more complicated than the respiratory system

39
Q

what does it mean if the urine is alkaline

A

the blood is alkaline

urinary system (9 decks)

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