What is sleep?

What is sleep?

People used to think of sleep as an activity where not much happened. Studies show, however, that the brain and body are very active while we sleep.

There are two kinds of sleep: non-rapid eye movement eye movement (NREM) and rapid eye movement (REM) sleep. These two states affect the body and mind in different ways.

NREM Sleep

Most of us, if we are lucky, fall asleep within 10 to 20 minutes of going to bed. Our bodies begin a cycle of sleep. The first four stages are NREM. Stages 1 and 2 are light sleep where we can be awakened easily and contractions of our muscles can be seen. In stages 3 and 4 our brain waves slow and we enter into deep sleep – it is very difficult to wake someone up in this stage. There is no eye movement or muscle activity at this point.

REM Sleep and Dreaming

The fifth stage of sleep occurs normally after about 90 minutes, and is characterized by dreaming and rapid eye movement. No other muscles move during this time. If you have the chance to watch a friend or family member sleep, check to see if their eyes are moving back and forth, like they are watching a movie underneath closed eyelids. If so, they are likely in the middle of a dream.

The cycles of NREM and REM sleep repeat throughout the night. The first period of dreaming only lasts five minutes. REM periods are longer with each subsequent cycle. We typically spend more than two hours each night dreaming