Answer :
Final answer:
The correct answer is: a) Higher O₂ levels decrease ventilation drive. Higher levels of oxygen in the bloodstream decrease the drive for ventilation, as the main regulator of breathing is carbon dioxide levels affecting blood pH. Breathing is centrally controlled mainly by CO₂ levels, not O₂ levels. Increased O₂ levels tend to reduce the ventilatory drive.
Explanation:
The correct answer is: a) Higher O₂ levels decrease ventilation drive. The relationship between O₂ (oxygen) and ventilation drive is vital for understanding how the body regulates breathing. High levels of O₂ in the bloodstream can decrease the ventilatory drive because the primary trigger for increasing ventilation is the level of carbon dioxide (CO₂) in the blood, which affects blood pH. Central control of breathing by the medulla oblongata is sensitive to CO₂ levels and the resulting pH changes, rather than directly to O₂ levels.
Alveolar ventilation can adjust through changes in both the respiratory rate and tidal volume, either by increasing the respiratory rate and decreasing tidal volume or vice versa, so the total ventilation remains the same to match oxygen demand. During situations where the O₂ levels are decreased, as might be encountered with a lower percentage of oxygen in the air, the body will respond by increasing ventilation to try and compensate for the reduced availability of oxygen, driving the muscles of respiration to work harder.
