Question:
In forceful expiration, which one of the following groups of neurons gets fired?
In forceful expiration, which one of the following groups of neurons gets fired?
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Quiet expiration is passive; the medullary group that powers active expiration is the answer.
Updated On: Jun 23, 2026
- VRG (Ventral respiratory group)
- DRG (Dorsal respiratory group)
- Pneumotaxic centre
- Chemoreceptors
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The Correct Option is A
Solution and Explanation
Step 1: The medullary respiratory centre in the medulla oblongata contains the dorsal respiratory group (DRG), the ventral respiratory group (VRG) and the pre-Botzinger complex.
Step 2: The DRG neurons are mainly concerned with inspiration. They descend to spinal motor neurons that drive the diaphragm and external intercostal muscles during quiet breathing.
Step 3: The VRG neurons are mainly concerned with forceful (active) expiration and contribute little to quiet inspiration. They activate the expiratory muscles such as the abdominals and internal intercostals when breathing becomes forced.
Step 4: The pneumotaxic centre lies in the pons and only modulates respiratory rhythm, while chemoreceptors sense gas tensions rather than firing expiratory muscles. Hence forceful expiration fires the VRG.
Step 2: The DRG neurons are mainly concerned with inspiration. They descend to spinal motor neurons that drive the diaphragm and external intercostal muscles during quiet breathing.
Step 3: The VRG neurons are mainly concerned with forceful (active) expiration and contribute little to quiet inspiration. They activate the expiratory muscles such as the abdominals and internal intercostals when breathing becomes forced.
Step 4: The pneumotaxic centre lies in the pons and only modulates respiratory rhythm, while chemoreceptors sense gas tensions rather than firing expiratory muscles. Hence forceful expiration fires the VRG.
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