Stages of sleep
Have you ever wondered what happens when you sleep at night? By that, meaning when you close your eyes to sleep, do you know what goes on within your body and more specifically, within your brain? That is because your brain is the one that controls your sleep, and it is still active even when you’re sleeping.
When you’re sleeping, the brain is sending out all kinds of signals, and many of these signals are controlling the various stages of sleep you will be undergoing. Things like muscle and eye movements, and internal organ activity, all change throughout the various stages of sleep.
There are 5 stages of sleep which if you get a good night’s sleep; your sleep cycle will pass through all of them a few times. The first 4 out of 5 stages, are grouped together, and classified as the non-rapid eye movement stage, or better known as NREM. The remaining fifth stage is called the rapid eye movement state, or REM state.
The changes in brain wave activity differentiate the NREM and REM states from each other. The REM stage also involves an irregular heartbeat, rapid breathing, increased blood pressure, and heightened activity within the brain. All this while, the muscles elsewhere in the body will be in a state of rest. The sleep that you experience during the first third of the night consists of mainly NREM sleep, but the last third of it will be REM sleep, which is what you will awaken from, after a night of “normal” sleep.
Stage 1 is a transitional period of light sleep. This sleep is light sleep, and it is easy to be aroused from this sleep. You might find yourself falling and waking several times. All people will have experienced hypnic myoclonia, which is a sudden contraction or jerking of the muscles. Also, feelings of drowsiness take over, and your eye movements will slow down. You may be aware of what’s going on, but slowly, you will sink deeper and deeper into sleep. The brain waves during this period, are in transition from alpha to theta waves.
Stage 2 makes up almost half of the entire sleeping period, during which the brain waves and heartbeat slow down even more, the eyes stop moving, and body temperature falls to a stable equilibrium. Occasionally, short periods of eye movement will occur. This is also the type of sleep that is not very refreshing or rejuvenating to the body. You need stage 3 and 4 for that.
Stage 3 and Stage 4 are the stages of deep sleep, during which the brain is in delta wave mode. Delta waves are really slow wave cycles. Bed wetting or sleep walking may occur during this phase. Stage 4 is really a more pronounced state of stage 3, and these 2 phases are important to getting a good night’s sleep.
Throughout the sleep period, the fifth stage, or the REM phase is actually taking place. REM sleep always follows a period of NREM sleep, and it makes up about 25 percent of the total time spent sleeping. The first REM occurs right after Stage 1 NREM, lasting for about 10 minutes, but the final REM stage lasts about an hour. A normal sleep period of 8-9 hours will have REM occurring about 4 to 5 times throughout the entire period. REM is the phase where the eyes are moving about rapidly, and dreaming occurs.
These phases of sleep repeat themselves throughout the night, and are called the sleep cycles. In a typical sleep period, the amount of REM sleep increases with the progression of the sleep cycles. Good quality sleep is an uninterrupted sequence of sleep cycles and REM sleep.