The Sleep/Waking Flip-Flop According to Saper et al. (2001), the major sleep-promoting region (the v

The Sleep/Waking Flip-Flop According to Saper et al. (2001), the major sleep-promoting region (the vlPOA) and the major          wakefulness-promoting regions (the basal forebrain and pontine regions that contain acetylcholinergic neurons; the locus coeruleus, which contains noradrenergic neurons; the raphe nuclei, which contain serotonergic neurons; and the tuberomammillary nucleus of the hypothalamus, which contains histaminergic neurons) are reciprocally connected by inhibitory GABAergic neurons. (a) When the flip-flop is in the “wake” state, the arousal systems are active and the vlPOA is inhibited, and the animal is awake. (b) When the flip-flop is in the “sleep” state, the vlPOA is active and the arousal systems are inhibited, and the animal is asleep.