Every night you go through different stages of sleep. One is REM sleep, the famous dream sleep. However, the majority is non-REM sleep (NREM), the ‘normal’ sleep .
These sleep stages not just walk together. There is a fixed order. And this whole list, called the sleep cycle, you go through four to six times a night. Below are the stages that you sleep a sleep cycle.
Transitional phase between waking and sleeping
The first sleep stage of NREM sleep is a transition phase between waking and sleep state. This stage lasts three to five minutes. The body temperature drops and the muscles relaxed.
During this stage, appearing slow eye movements (slow eye movements or SEM). You probably know that feeling when you’re fighting your sleep. Your eyes slowly turning away and you’re struggling to keep them open.
In this phase, you often feel a shock, sometimes with the feeling that you fall. This is a sleep twitch; a brief contraction in the muscles of your arms or legs. You’ll be back here fully awake. Also sounds you are still easily at this stage awake .
The second sleep stage is something deeper and lasts about thirty to forty minutes. In this sleep stage sleep you most: up to 50 percent of total sleep time per night. It is the beginning of the ‘real’ sleep. You are at this stage not just wake up every sound.
Very deep sleep
Stage three and four are usually considered as a whole. In this phase you are very relaxed and difficult to arouse. Your breathing is deep and your heartbeat is slow and steady.
At the beginning of the night it lasts very long. However, in the following cycles, this phase lasts shorter and shorter. There are growth hormone release, your body is recovering and doing new force.
As you get older, these deep sleep stages last shorter. You will therefore find that sleep is far less refreshing than before.
After stage four starts the stage of REM sleep or dream sleep. The large muscles of your limbs are paralyzed. If this were not so, you could jump out of bed to make your dreams.
You can tell if someone is in his REM sleep with rapid eye movement under closed eyelids. The brains are very active during this phase. Why brains are so active, there still are scientists. But it is suspected that it has to do with processing information.
As the night progresses, REM sleep periods are getting longer. In total, the increases dreaming sleep 20 to 25 percent of sleep time consuming.