How does sleep work?
Waking refreshed from a sound night’s sleep is natural enough for many of us, but nearly impossible for others. So, why do some people spend their nights tossing and turning, and others sleep “like a baby?” For many, it’s because of the disruption of circadian rhythms—the body’s internal clock. This biological clock follows the 24-hour cycle of the sun (our normal day) and is fundamental to all living organisms, influencing hormones that impact sleep, metabolic rate and temperature. When it is disrupted by changes in the sleep and wake schedule, sleep loss is the result. During sleep, we pass through five phases, with REM (rapid eye movement) being the fifth stage. The sleep cycle begins at stage one, progresses to REM and starts all over again. During phase one, you can be awakened very easily. As you progress into the deep sleep of stages three and four, there is no eye or muscle movement. It is very difficult to wake someone in these latter stages. When you move into REM sleep (usua
