Question

In forceful expiration, which one of the following groups of neurons gets fired?

• A. VRG (Ventral respiratory group)
• B. DRG (Dorsal respiratory group)
• C. Pneumotaxic centre
• D. Chemoreceptors

Hint:

Quiet expiration is passive; the medullary group that powers active expiration is the answer.

Answer 1

The Correct Option is A

Step 1: Breathing is driven by neuron pools in the medulla, split into a dorsal group for inspiration and a ventral group for active breathing.
Step 2: During calm breathing the dorsal respiratory group runs the diaphragm and external intercostals, and expiration is passive.
Step 3: When expiration must be forced, the ventral respiratory group switches on and recruits the abdominal and internal intercostal muscles to push air out actively.
Step 4: The pontine pneumotaxic centre only fine-tunes timing, and chemoreceptors merely report blood gas changes, so neither fires forced expiration. The active expiratory driver is the VRG.
\[\boxed{\text{VRG}}\]