lecture 7a: acid-base regulation

Question 1

amount of volatile acid excreted by lungs vs kidneys

Answer 1

lungs: 99%, kidneys: 1%

Question 2

blood pH range

Answer 2

7.35-7.45 as this is regulatee

Question 3

urine pH range

Answer 3

5-9 as this is regulator (so broad range)

Question 4

where is HCO3- reabsorbed in nephron (fully reabsorbed)

Answer 4

80% PCT, 10% ascending limb, 6% DCT, 4% collecting duct

Question 5

HCO3- buffer

Answer 5

IC and EC buffer that responds to changes in metabolic acid; can be produced from volatile respiratory acid

Question 6

Henderson-Hasselbach equation for pH

Answer 6

pH = pK +log10 ([HCO3-]/[CO2]); pK is 6.1

Question 7

Davenport diagram - definitely copy the diagram

Answer 7

pH at bottom (log transformation), [H+] at top (this axis is not linear); [HCO3-] on left y-axis; PCO2 on own axis within top right corner

Question 8

Davenport diagram

Answer 8

green areas are normal ranges and where all cross is normal range for all

Question 9

metabolic alkalosis

Answer 9

curves up top right as almost moves along PCO2 lines (gradient becomes steeper as hypoventilation); increase in pH and HCO3-

Question 10

metabolic acidosis

Answer 10

curves down bottom left as decrease in HCO3-, pH and PCO2 (gradient becomes shallower as hyperventilation)

Question 11

chronic respiratory acidosis

Answer 11

curves up top left as decrease in pH and increase in HCO3- and PCO2; large broad overlap with normal pH as physiology can change to bring pH back down

Question 12

acute respiratory acidosis

Answer 12

linear very left and slightly up; narrow; big decrease in pH and small increase in HCO3-; larger increase in PCO2

Question 13

chronic respiratory alkalosis

Answer 13

linear bottom right but more bottom than right); increase in pH with decrease in PCO2 but large decrease in HCO3- to compensate; significant overlap with normal pH as physiology can change to bring pH back down

Question 14

acute respiratory alkalosis

Answer 14

linear bottom right but more right than bottom; increase in pH with bigger decrease in PCO2 and smaller decrease in HCO3-

Question 15

HCO3- reabsorption after filtration into tubule lumen

Answer 15

HCO3- and H+ via carbonic anhydrase to H2O and CO2; CO2 moves into cell; reverse reaction IC so H+ and HCO3- in cell; H+-ATPase (primary) or Na+/H+ antiporter (2ndry active transport) pumps H+ out; HCO3- into capillary by chloride bicarbonate exchanger or sodium bicarbonate contransporter; restore Na+ balance exchanged in basal membrane by Na+/K+-ATPase; Cl- returns to interstitium by Cl- channels

Question 16

acid-secreting cell intercalating cells of collecting duct

Answer 16

alpha cell

Question 17

HCO3- secreting cell intercalating cells of collecting duct

Answer 17

beta cell (can both change into each other)

Question 18

alpha cell

Answer 18

HCO3- in same way; H+ out of apical membrane (Na+/H+ symptorter, H+/K+-ATPase antiporter, H+-ATPase); save HCO3- also to do more buffering (mop up protons) so exchanged into capillary by Cl-/HCO3- exchanger

Question 19

beta cell

Answer 19

same mechanisms but apical and basolateral flipped; H+ pumped into capillary, HCO3- exchanged out

Question 20

if no HCO3- to save, must be generated

Answer 20

glutamine split into HCO3- (absorbed) and NH4+ (removed)

Question 21

HPO42- in filtrate

Answer 21

HCO3- (exchanged into capillary) and H+ produced by carbonic anhydrase IC and pumped out and combines with HPO42- to form H2PO4- so allows information of what happens in kidneys

Question 22

fully compensated respiratory acidosis

Answer 22

base excess and PCO2 are abnormal in same direction (higher)

Question 23

fully compensated respiratory alkalosis

Answer 23

base excess and PCO2 are abnormal in same direction (lower)

Question 24

fully compensated metabolic acidosis

Answer 24

base excess and PCO2 are abnormal in same direction (lower)

Question 25

fully compensated metabolic alkalosis

Answer 25

base excess and PCO2 are abnormal in same direction (higher)

Question 26

how can metabolic acidosis and alkalosis coexist

Answer 26

HCl excreted by vomiting but lactic acid accumulation