The stages of sleep
The stages of sleep
During sleep, the body moves between REM (rapid eye movement) and non-REM sleep in cycles. Each type of sleep is linked to specific brain activity. The body cycles through three stages of non-REM sleep and REM sleep several times during the night with REM sleep becoming increasingly deeper and longer towards the morning.2
- Stage 1 non-REM sleep
The transition period from being awake to sleeping; a person’s eyes are closed but it is easy to wake them up. Brain activity, heart rate, breathing and eye movements start to slow down and the muscles start to relax.2,3
- Stage 2 non-REM sleep
Light sleep where the body temperature drops and eye movements stop. Brain activity, heart rate and breathing continue to slow down and muscles relax further.2,3
- Stage 3 non-REM sleep
When deepest sleep occurs; heart rate and breathing slow to their lowest levels during sleep and the muscles are completely relaxed. It is difficult to rouse someone from this stage of sleep; if they are woken up, they may feel disorientated for a few minutes. During this stage, the body repairs tissues, builds bone and muscle, strengthens the immune system and builds up energy for the next day.2,3
- REM sleep
Occurs about 90 minutes after falling asleep. The eyes move rapidly from side to side while they are closed and brain activity increases. Breathing becomes faster and irregular, heart rate and blood pressure increase. Dreaming occurs mostly during REM sleep; the body becomes relaxed and immobilised, which prevents the person from acting out their dreams. REM sleep is important for learning and memory; this is when the brain processes information that has been taken in during the day and stores it in the long-term memory.2,3