The sleep-wake cycle is regulated by a 'flip-flop' model involving mutual inhibition between sleep-promoting and wake-promoting nuclei. Which nucleus serves as the primary sleep-promoting center that releases GABA and galanin to inhibit arousal centers?
- A Ventrolateral preoptic nucleus (VLPO) ✓
- B Tuberomammillary nucleus
- C Locus coeruleus
- D Pedunculopontine tegmental nucleus
Correct answer: A. Ventrolateral preoptic nucleus (VLPO)
Explanation
The ventrolateral preoptic nucleus (VLPO) in the anterior hypothalamus is the primary sleep-promoting center. It releases GABA and galanin to inhibit all major arousal centers (locus coeruleus, tuberomammillary nucleus, raphe nuclei, LDT/PPT). The locus coeruleus and tuberomammillary nucleus are wake-promoting. Bilateral VLPO lesions cause insomnia. This reciprocal inhibition creates stable sleep or wake states.
Reference: Ganong's Review of Medical Physiology, 26th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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