[Campbell Biology P.996] If an individual consciously forced more air out of their lungs wit... | Practice Question

If an individual consciously forced more air out of their lungs with each exhalation hyperventilation , how would this likely affect the partial pressures of gases in the alveolar spaces and the subsequent gas exchange?

  • A: The alveolar PO2 would decrease, and PCO2 would increase, impeding O2 uptake and CO2 release.
  • B: The alveolar PO2 would increase, and PCO2 would decrease, enhancing both O2 uptake and CO2 release.
  • C: Both alveolar PO2 and PCO2 would decrease, leading to reduced gas exchange efficiency.
  • D: There would be no significant effect on alveolar gas partial pressures, as the body's compensatory mechanisms would immediately stabilize them.

Explanation

Forcing more air out of the lungs with each exhalation, especially if combined with deeper inhalations, would increase the rate of ventilation. This would bring more fresh atmospheric air high PO2, very low PCO2 into the alveoli, effectively 'washing out' more CO2 and increasing the PO2. Consequently, the partial pressure gradient for O2 between the alveoli and blood would steepen, enhancing O2 uptake, and the gradient for CO2 would also become steeper, enhancing CO2 release from the blood into the alveoli.