What Are the Nuts and Bolts of Sleep and Its Regulation?

The neurophysiologic basis of sleep is rooted in the function of specific brain structures and neurotransmitter systems that mediate and modulate wakefulness and sleep in a synchronized fashion. Indeed, it is the interaction among these neural systems and structures that underlie the specific features of rapid eye movement (REM) and non-REM sleep. In addition to these complex neurophysiologic mechanisms, a simpler and more intuitive 2-process model of sleep-wake regulation composed of the intrinsic sleep drive (Process S) and an opposing circadian alerting system (Process C) is also a useful construct to consider when approaching a patient with a potential sleep disorder. A basic familiarity with these neural mechanisms, coupled with an understanding of the importance of a smooth and regular sleep-wake cycle, governed by the 2-process model, should provide a robust understanding of how sleep is regulated during the 24-hour day.