phy 22 - aimhigh

[ArchivalUser]

28. A 24-year-old man climbs a 10,000-foot mountain during
a college fraternity expedition. During his ascent, he
becomes light-headed and begins to hyperventilate.
Which of the following sets of physiologic changes
would be expected in this man?
Plasma pH ,Plasma PCO2, Renal H+Secretion

(A) ↑ ↑ ↑
(B) ↑ ↑ ↓
© ↑ ↓ ↑
(D) ↑ ↓ ↓
(E) ↓ ↓ ↓
(F) ↓ ↓ ↑
(G) ↓ ↑ ↓
(H) ↓ ↑ ↑

[ArchivalUser]

f .

[ArchivalUser]

D.

[ArchivalUser]

H?

[ArchivalUser]

d.

[ArchivalUser]

D...

Thnx for the Qs aimhigh!

[ArchivalUser]

28. The correct answer is D. The ascent to high altitude
lowers oxygen levels in the arterial blood (hypoxemia).
At altitudes that cause the alveolar PO2 to approach 65
mm Hg, hypoxemia-induced hyperventilation is
prominent. The hyperventilation causes CO2 to be
œblown off, which lowers the PCO2 of the blood
(hypocapnia) and increases the blood pH (alkalemia).
The decreased PCO2 reduces tubular secretion of H+
ions so that bicarbonate reabsorption is not complete.
This loss of bicarbonate (increased bicarbonate excretion)
lowers the plasma bicarbonate concentration and
thus lowers the blood pH back toward normal. Renal
compensation begins rapidly, but it takes 3 to 5 days for
the plasma bicarbonate concentration to reach its full
compensatory level. Therefore, hyperventilation
decreases CO2 levels, increases the blood pH, and
decreases H+ secretion by the kidneys.

[ArchivalUser]

tricky Q...thanks a lot for the explanation Aimhigh....

[ArchivalUser]

by the way these r not my explanatrions