A secondary respiratory drive that responds to low oxygen levels in the blood.

• A. Ventilatory Drive
• B. Carbonic Drive
• C. Hypoxic Drive
• D. Neural Drive

Answer: (C)

Breathing is normally driven primarily by CO2 levels, sensed by central chemoreceptors. When oxygen levels fall, a secondary cue kicks in: the hypoxic drive. This response is carried by peripheral chemoreceptors in the carotid bodies that detect low PaO2 and send signals to the brainstem to increase ventilation. It becomes especially relevant when CO2-driven drive is reduced or in certain chronic lung conditions, where the body relies more on low oxygen to stimulate breathing. The other terms don’t specifically describe a response to low blood oxygen: ventilatory drive is the general urge to breathe, carbonic drive isn’t the standard term for CO2-based control, and neural drive is a broad, non-oxygen-specific mechanism.