Which structure regulates natural ventilation by detecting carbon dioxide levels and oxygen levels?

• A. Cerebellum
• B. Medulla
• C. Pons
• D. Cortex

Answer: (B)

Ventilation is controlled by automatic neural circuits in the brainstem, with the medulla oblongata playing the central role. It houses the primary respiratory centers and central chemoreceptors that monitor CO2 levels through changes in CSF pH. It also receives input from peripheral chemoreceptors in the carotid bodies that detect O2 (and CO2/pH in blood) and adjust breathing accordingly. This integration of CO2 detection and oxygen sensing drives the automatic adjustments of breathing to maintain blood gas balance. The cerebellum doesn’t regulate breathing, the pons mainly modulates rhythm rather than detecting gas levels, and the cortex governs voluntary control rather than automatic regulation.