Sleep Cycle
Sleep goes through a cycle which reoccurs a number of times every night. Understanding this can help you to improve your sleep. Sleep is controlled by the internal body clock. It varies depending on light, the time and any cues the body may use to identify the time of day. During sleep the cycle goes from deep sleep to more alert phases. As the night continues more time is spent dreaming and lighter sleep. Each stage of the sleep cycle is important but deep sleep and REM sleep are thought to be most vital
Stages of the sleep cycle
- Drowsiness (Stage 1) - this normally lasts up to 10 minutes, the visible signs are that the eyes move slowly, and muscle activity reduces, in this stage it is easy to wake someone.
- Light sleep (Stage 2)- in this phase the movement of the eye stop, the heart rate goes down and the temperature of the body goes down, it is easy to awaken from this phase.
- Deep sleep (Stage 3 + 4)- it is hard to awaken someone from this phase, and if they are awoken they are generally groggy and it takes a while to recover. Blood flow decreases to the brain and goes to muscles restoring physical energy. Immune function is also heighten during deep sleep.
- REM sleep also known as Dream Sleep - occurs from 70 to 90 minutes into the sleep cycle. During the night there are normally 3-5 REM sections every night. This stage is associated with emotions, memories and stress relief. During this phase breathing can be rapid, irregular and shallow, heart rate heightens, blood pressure increases, and arousal may occur.