Stimulation of the pontine pneumotaxic centre (pontine respiratory group) produces which effect on the breathing pattern?
- A Prolongs inspiration and produces apneusis
- B Directly generates the automatic respiratory rhythm independent of the medulla
- C Shortens inspiration and switches off the inspiratory ramp earlier, increasing respiratory rate ✓
- D Inhibits expiration and prolongs the expiratory pause
Correct answer: C. Shortens inspiration and switches off the inspiratory ramp earlier, increasing respiratory rate
Explanation
The pontine respiratory group in the upper pons modulates the medullary inspiratory ramp by limiting its duration, acting as an inspiratory off-switch. Stronger pneumotaxic activity shortens inspiration, reduces tidal volume and raises respiratory rate. Apneusis occurs when this upper pontine influence is lost along with vagal input, not when it is stimulated, which eliminates option A. The rhythm generator itself lies in the medulla, so option B is incorrect.
Reference: Ganong's Review of Medical Physiology, 27th ed.
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