What would happen to the sleep–wake schedule of someone who lacked orexin?
Orexin is a neuropeptide and is synthesized by a neuron cluster in the lateral part of the hypothalamus area. This neuropeptide receives signals related to emotional, physiological and environmental stimuli. Orexin neurons regulate a variety of body functions. This includes sleep/wake states, energy homeostasis, feeding behavior, cognition and mood. Furthermore, abnormalities in orexin levels may be a result of an underlying pathological condition.
The orexin system is critical to maintain wakefulness. Orexin deficiency results in narcolepsy. This is a neurological disease characterized by sleep attacks and chronic daytime sleepiness. Additionally, cataplexy, hallucinations, and sleep paralysis are other associated conditions. Narcolepsy is due to loss of orexin-containing neurons.
A variety of neurotransmitters regulate orexin neuron activity. GABA, noradrenaline, and serotonin are inhibitors. On the other hand, dopamine is an activator.
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