Question

Assume your blood has a pH of 7.4 and you have been producing urine with a pH of 7.4 for a while. You drive to very high altitude (ca. 4,000 m) and spend several hours there. Your alveolar ventilation rate increases (as expected), and eventually this causes your blood pH to rise above 7.4 (your blood plasma becomes more basic than normal).
This change in blood pH will initiate compensatory homeostatic mechanisms in your kidneys ("renal compensation") that will alter the pH of your urine so as to bring your blood pH back down toward the normal value of 7.4. What pH will your urine have to be in order to begin to drop your blood pH back toward normal?

A) Higher than 7.4 (more basic than normal)

B) 7.4

C) Lower than 7.4 (more acidic than normal)

Answer 1

Answer : (A) Higher than 7.4 (more basic than normal)

When the alveolar ventilation rate increases, this causes CO2 washout and hence Respiratory alkalosis.

Now, as a compensatory mechanism, the kidneys excrete more bicarbonate and less H+. Hence urine pH increases. i.e PH > 7.4

----------------------------------------------------------------------------------------------------------------------------------------

NB: The basic concept is....In alkalosis, the blood is basic. So, the excess base has to be removed through the urine. Therefore, the urine will have to be more basic.