Final answer:
The primary regulator of the magnitude of ventilation under normal circumstances is the control of ventilation centers in the brain. These centers signal the muscles involved in pulmonary ventilation to contract, resulting in a rhythmic and consistent ventilation rate.
Step-by-step explanation:
The primary regulator of the magnitude of ventilation under normal circumstances is the control of ventilation centers in the brain. These centers signal the muscles involved in pulmonary ventilation to contract, resulting in a rhythmic and consistent ventilation rate. The control of ventilation is a complex interplay of multiple regions in the brain, ensuring sufficient oxygen intake and carbon dioxide removal.