Jan10 M1-Acid Base Physiology

Question 1

lower and upper limit of pH before death

Answer 1

6.8 to 8.0

Question 2

pH formula

Answer 2

-(log H+)

Question 3

blood pH formula

Answer 3

6.1 + log (bicarb/0.03PCO2) = pH

Question 4

3 values to check for acid base balance

Answer 4

pH, CO2, bicarb

Question 5

rule in HCO3 and CO2 variation

Answer 5

always move in the same direction, no matter which one is the primary problem

Question 6

how to know if problem is primarily respiratory or metabolic

Answer 6

if pH and CO2 change in same direction, metabolic

if pH and CO2 change in opposite direction, respiratory

Question 7

how much CO2 prod daily and how

Answer 7

15000 mmol. because of the Krebs cycle

Question 8

2 types of acids in the body and what they correspond to

Answer 8

carbonic acid (volatile): CO2
non-carbonic acid (non-volatile): lactic, phosphoric, sulfuric

Question 9

non-carbonic acids source and how much produced daily

Answer 9

from a.a metabolism. 50-100 mmol

Question 10

buffer def

Answer 10

any substance that can reversibly bind H+ ions

Question 11

how H+ ions are buffered in the body

Answer 11

by extracellular (HCO3, etc.) and intracellular buffers

Question 12

major intracellular buffers

Answer 12

phosphates, proteins and carbonate (CO3) in bone

Question 13

2 steps to acid metabolism in the body

Answer 13

1. buffering

2. excretion

Question 14

how much acid do the kidneys and the lungs excrete daily

Answer 14

lungs: 15000mmol
kidneys: 50-100 mmol

Question 15

in the kidney, excreting acid is the equivalent of what

Answer 15

generating bicarb (50-100 mmol daily)

Question 16

minimal tubular pH and what takes care of buffering there

Answer 16

4.5

ammonium (NH4+) and hydrogen phosphate (HPO4 2-)

Question 17

where are acids handled in the tubules

Answer 17

PCT, loop of Henle, CD

Question 18

main thing kidney does to keep the serum bicarb

Answer 18

reabso of filtered bicarb

Question 19

how is bicarb reabsorbed at the tubules (PCT)

Answer 19

1. H+ pumped out via Na-H exchanger
2. H+ and bicarb form CO2 (via luminal CA)
3. CO2 enters membrane and becomes H+ and bicarb via cellular CA
4. bicarb in blood via Na-3bicarb cotransporter
5. H+ out again

Question 20

CA inhibitors inhibit what CAs and consequence on urine, what is excreted

Answer 20

CA in and out of the cell inhibited. No more H+ made so Na-H exchanger stops working. Pee NaHCO3

Question 21

CAi used for what (2)

Answer 21

glaucoma and mountain sickness

Question 22

principle of using CA in mountain sickness

Answer 22

you hyperventilate because of the hypoxia so lose a lot of CO2, become alkalotic. CA stops that by inhibiting PCT reabso of bicarb

Question 23

can you induce alkalosis by ingesting too much bicarb?

Answer 23

no, excess filtered at kidney is excreted

Question 24

2 ways for the kidney to generate new bicarb and why must do that

Answer 24

1. urine buffering by H-HPO4 adds 1 bicarb to plasma
2. urine buffering by ammonium adds 1 bicarb to the plasma
   * necessary bc need NEW bicarb to buffer the NEW acid. (good to reabso bicarb but need new)

Question 25

when does the kidney start to use H-HPO4 urine buffering (one method to make new bicarb)

Answer 25

when there is no more bicarb available in the tubule and all has been reabso

Question 26

Urine buffering by H-HPO4: how it works to generate a bicarb

Answer 26

CA in the cell makes H+ and HCO3- from H2O and CO2. H+ out to bind HPO4 and form H2PO4. bicarb in

Question 27

Urine buffering by ammonium: how it works to add 1 bicarb to the plasma

Answer 27

1. glut reabso at PCT via Na-a.a cotransporter 2. glut forms NH4+ + bicarb and bicarb taken in 3. NH4+ out via Na-H exchanger (takes H+'s spot)

Question 28

main adaptive response to an acid load and how much bicarb it produces daily

Answer 28

NH4+ excretion. makes 30-40 mmol daily

Question 29

other way to secrete NH4+ coming from glutamine than Na-H cotransporter

Answer 29

NH3 in the cell diffuses in the lumen and binds an H+ to make ammonium

Question 30

other place in the tubule where there is acid handling and what mechanism is used

Answer 30

loop of Henle. 1st mech for new bicarb. H2O and CO2 make HCO3 and H+ via CA. HCO3 in via Na-HCO3 cotransporter. H+ out via Na-H exchanger

Question 31

what is the main determinant of acid excretion and how it works (acts on what)

Answer 31

low extracellular pH acts on 2 mech for new bicarb bc low pH = acid load - revs up Na-H antiporter in PCT - increases glut uptake and metab by PCT - revs up Na-3 bicarb cotransporter in PCT - revs up H-K activity in CD (alpha-int) - promotes ammonium excretion

Question 32

H+ handling in the CD (2 things)

Answer 32

1. alpha-int cells have H+ (out) K (in) exchanger ATPase (and then bicarb-Cl exchanger) 2. NH3 that diffused out into the tubule lumen becomes NH4+ bc of that acid and goes out

Question 33

how to maintain acid base balance in renal failure

Answer 33

IV D5W + bicarb (hypertonic but sugar quickly metab)

Question 34

normal arterial and venous pH, H+, CO2 and bicarb values

Answer 34

arterial: 7.4, 40, 40, 24 venous: 7.45, 45, 45, 25

Question 35

causes of metabolic acidosis

Answer 35

diarrhea (loss of bicarb), renal failure, poisoning, diabetic ketoacidosis, lactic acidosis

Question 36

2 responses to metabolic acidosis

Answer 36

1. buffering by IC and EC buffers | 2. compensatory rise in ventilation

Question 37

2 causes of metabolic alkalosis

Answer 37

vomiting, hyperaldo (increased H secretion in DCT and CCD bc revs up H-K ATPase in alpha int)

Question 38

2 causes of respiratory acidosis

Answer 38

acute respiratory failure (morphine) | COPD (chronic)

Question 39

compensation to metabolic alkalosis

Answer 39

less bicarb reabso

Question 40

compensation to resp acidosis

Answer 40

kidney increases acid (mostly NH4+ excretion)

Question 41

4 causes of resp alkalosis

Answer 41

pneumonia, anxiety, pregnancy, mountaineering

Question 42

why pregnancy causes resp alkalosis

Answer 42

medulla stimulated at lower CO2 (stimulates breathing at lower CO2)

Question 43

contraction alkalosis def

Answer 43

volume contraction state where all bicarb is retained

Question 44

ions left and ions reabsorbed in contraction alkalosis + their urine amount

Answer 44

Na and bicarb all reabsorbed (PCT important) | Cl low in serum and low in urine bc is lost in the fluid loss

Question 45

why can't excrete bicarb in contraction alkalosis

Answer 45

because Na reabsorbed at PCT so bicarb too. if euvolemic, less Na-H exchanger work so more H left in the cell and unavailable to bind bicarb in urine to make it enter the PCT so bicarb stays in the urine

Question 46

how to treat contraction alkalosis

Answer 46

give NS so that Na not too retained anymore