Which structure is regarded as the principal site of respiratory rhythm generation in the mammalian brainstem?
- A Pre-Botzinger complex in the ventrolateral medulla ✓
- B Pneumotaxic center in the upper pons
- C Apneustic center in the lower pons
- D Dorsal respiratory group of the nucleus tractus solitarius
Correct answer: A. Pre-Botzinger complex in the ventrolateral medulla
Explanation
The pre-Botzinger complex, a network of pacemaker-like neurons in the rostral ventrolateral medulla, generates the basic respiratory rhythm. The pontine pneumotaxic center modulates inspiratory duration and switches inspiration off, while the apneustic center promotes inspiration and is not essential for rhythm. The dorsal respiratory group integrates sensory input and drives inspiration but receives rhythm from medullary generators.
Reference: Ganong's Review of Medical Physiology, 27th ed.
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