Sleep is an important part of daily life. The quality of your sleep often dictates how you feel, think and function during your waking hours and also how your body recovers from the ordeals of the day. But even in sleep, your brain and your body remain active. Sleep is sort of the body’s maintenance time, when the body removes toxins, repairs cells and creates neural pathways.
Exactly what happens when you sleep? Here’s a look at the different sleep stages so you can appreciate the value of a good night’s sleep.
Stages of sleep
You actually experience two basic kinds of sleep. One is rapid eye movement sleep or REM sleep and the other is non-REM sleep. Each type is associated with specific brain waves and brain activity. Non-REM sleep has three different stages, each of which can last from 5 to 15 minutes, and you cycle through them along with REM sleep multiple times. The stages of non-REM sleep are when the body regrows and repairs tissues, strengthens the immune system and builds muscle and bone.
Stage 1 non-REM sleep
In this sleep stage, you transition from wakefulness to slumber. During this period of light sleep, your muscles start to relax and twitch on occasion. Your eye movements, breathing and heartbeat slow down, and your brain waves also start to ease from the daytime patterns of wakefulness to a more subdued state.
Stage 2 non-REM sleep
This is also a stage of light sleep and occurs just before you enter a deeper sleeping stage. Your muscles relax more and your breathing and heartbeat continue to slow down. Your eye movements stop and your body temperature cools down. Your brain waves lessen in activity but it’s replaced by short bursts of electrical activity. Repeated sleep cycles are spent more in stage 2 non-REM sleep than in other stages of sleep.
Stage 3 non-REM sleep
This deep sleep stage happens in longer periods during the first half of your sleeping hours. This is the stage where your breathing and heart rate are at their lowest levels, the brain waves are a lot slower and the muscles are completely relaxed. When a person enters stage 3 sleep, he or she may be difficult to rouse. This is the sleep stage you need to feel refreshed and energized when you wake up.
Rapid eye movement sleep is called such because during this time, your eyes move quickly from side to side while your eyelids are closed. You first enter REM sleep around 90 minutes after you have gone to sleep, and this will typically last for 10 minutes. As you cycle through the different sleep stages, your REM sleep stages get longer – your last REM sleep may last up to one hour.
During REM sleep, brain activity is characterized by mixed frequencies and becomes closer to that experienced in wakefulness. In this sleep stage, your blood pressure and heart rate increase, and you start breathing faster at an irregular rate.
It is during REM sleep that you dream the most. You can dream in different stages of sleep but dreams are usually the most vivid in REM sleep. What’s interesting is that during this stage, your leg and arm muscles become paralyzed temporarily, which is why you can’t act out your dreams.