Northwestern University Feinberg School of Medicine

Center for Circadian and Sleep Medicine

About Sleep

The function of sleep is not fully understood, but it is generally accepted that it allows the body to recover from previous wakefulness and prepare for functioning during the subsequent waking period. Sleep is believed to be controlled through a diffuse system of neural networks located throughout the brain.

During sleep, the brain cycles between a deep, synchronized state of sleep and lighter, more active stage known as Rapid Eye Movement (REM) sleep. Over the course of a night a typical person will cycle through these stages about three to five times.

Circadian Rhythms

Circadian rhythms are internally generated signals that coordinate our bodily functions throughout the day. Alertness, body temperature, activity, sleep, and hormone release are a few of the processes that the circadian rhythm orchestrates. Although nearly every cell in the body has its own timing mechanism, all are coordinated through the master pacemaker located in the suprachiasmatic nucleus (SCN) of the brain.

Disruption of the body’s internal clock can result from short-term disturbances such as traveling across time zones (jet lag) or from a longer-term perturbation such as working odd hours or a constantly changing schedule. In some cases, the disturbance can be due to a genetic disorder which impairs an individual’s ability to synchronize with the outside world. Usually a disruption of the circadian system results in deficits in alertness and difficulty sleeping and can contribute to overall fatigue.

Sleep Disorders and Conditions

Get descriptions and more information on the conditions addressed by our center, both though research and clinical trials through the Northwestern Medicine’s Sleep Disorder Center website.