Lecture 27 - Acid/Base Physiology 2

Question 1

Respiratory regulation?

Answer 1

PaCO2 and pH sensed by chemoreceptors in the medulla & aortic/carotid bodies (hypoxia also for peripheral receptors), PaO2 is non-linear stimulus to ventilation, PaCO2 linear, potent stimulus to ventilation

Question 2

Maintenance and control of bicarbonate requires?

Answer 2

rebsorption of all HCO3- filtered by kidneys, regeneration of all HCO3- lost n the buffering of nonvolatile acids, removal of fixed acids incorporated into non-bicarbonate buffer systems

Question 3

Na movement of kidney cell?

Answer 3

Basolateral ATPase (3Na 2K) and luminal facilitated diffusion (leaving a negative potential)

Question 4

Secondary active secretion: Na-H+ antiporter and & HCO3

Answer 4

NaHCO3 of lumen breaks, Na through Na-H+ antiporter into call, H+ forms H2CO3 then H2O and CO2, CO2 diffuse into cell, CA rapidly pseudotransports as H2CO3, becomes H+ (out of antiporter) and HCO3
-> through Na-HCO3 sympoter into peritubular capillary

Question 5

Renal excretion of H+, regeneration of HCO3- and glucose, w acidification of NH4?

Answer 5

DRAW IT (2 parts) (w phosphate of part 3)

Question 6

Renal acid base regulation?

Answer 6

in acidosis/alkalosis secretion of H+ by the nephron is increased/decreased and HCO3 reabsorption is near complete/decreased

Question 7

HCO3- and Cl-?

Answer 7

inversely related, Cl- required to maintain electroneutrality e.g. volume loss due to diuretics or vomiting

Question 8

HCO3- and K+?

Answer 8

inversely related, increased by increased levels of adrenal corticosteroids (Cushing’s) - high aldosterone -> high Na reabsorption + high K+ and H+ losses (Na/H antiporter); H+ loss matched w high HCO3 reabsorption -> metabolic alkalosis w hyperchloraemia and hypokalaemia as well as expanded ECF volume

Question 9

Response to respiratory alkalosis?

Answer 9

hyperventilation reduces PCO2 and pH, reduced net renal acid excretion restores pH but reduces HCO3-

Question 10

Response to metabolic acidosis?

Answer 10

accumulation of lactic acid reduces pH and HCO3-, increased ventilation increases pH but reduces PCO2