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Hypocretin (orexin) system. The sleep-wake cycle is governed by a complex, multilevel neuronal system in the brainstem, thalamus, hypothalamus and basal forebrain. Hypocretin-producing neurons in the hypothalamus stabilise the activity of other key neuronal groups involved in the control of sleep and waking. These nuclei and their principal neurotransmitters are shown here in highly schematic fashion. Reproduced with permission from BMJ Publishing Group Ltd.13
