There are 2 main type of sleep: Rapid Eye Movement (REM) or Non-rapid Eye Movement (NREM). Sleep is classified into 4 stages: stage 1, stage 2, stage 3, and stage 4. After you progressed from stage 1 to stage 4, then you will go on into REM sleep. The complete cycle lasts for about 90 minutes. Therefore, an average adult will have 4 to 6 cycles each night.
Stage 1: Light Sleep
During first stage of sleep, we are in between awake and falling sleep. It usually last from 10 to 15 minutes. It is meant that we can be woken up easily. Our brain waves begin to slow down and our muscle activity will start to slow down and relax. This stage only occupies 2 to 5 percent of sleep time.
Stage 2: Light-Intermediate Sleep
After 10 minutes of stage 1, we will enter into stage 2. It will last for about 20 minutes. Our eyes movements stop and our brain waves slow down further. The breathing pattern and heart rate also start to slow down. Our body temperature will drop too. This stage will take up to 45 to 55 percent of our sleep time.
Stage 3 and 4: Deep Sleep
In stage 3, our brain start to produce delta waves which high amplitude (large) and low frequency (slow). Our breathing and heart rate also turn into slowest rate. Besides that, our blood pressure falls and body temperature also falls even lower. Our kidney function will be reduced, so we will produce less urine. In this moment, growth hormone will be released. This hormone will help to repair and maintain our immune system and body tissues. Therefore, insufficient deep sleep will affect our health.
In stage 4, it is characterized by rhythmic breathing and limited muscle activity. It occupies 40 percent of our sleep. It is difficult to rouse people from this stage. If we are woken during deep sleep, we cannot adjust ourselves immediately. Therefore, we will feel groggy and disoriented for several minutes.
REM sleep:
This stage will start about 70 to 90 minutes after we fall into deep sleep. Our brain start to active in this stage; sometime it will more active than we are awake. This is the period we dream the most. We will spend at least 2 hours dreaming every night. Sometime we will remember it, but sometime not. We can recall our dream in first few minutes after we wake up, because we can remember our dream from REM sleep, and most REM sleep takes place in the early hours. According to research, women are better than men at remembering their dreams.
Stage 1: Light Sleep
During first stage of sleep, we are in between awake and falling sleep. It usually last from 10 to 15 minutes. It is meant that we can be woken up easily. Our brain waves begin to slow down and our muscle activity will start to slow down and relax. This stage only occupies 2 to 5 percent of sleep time.
Stage 2: Light-Intermediate Sleep
After 10 minutes of stage 1, we will enter into stage 2. It will last for about 20 minutes. Our eyes movements stop and our brain waves slow down further. The breathing pattern and heart rate also start to slow down. Our body temperature will drop too. This stage will take up to 45 to 55 percent of our sleep time.
Stage 3 and 4: Deep Sleep
In stage 3, our brain start to produce delta waves which high amplitude (large) and low frequency (slow). Our breathing and heart rate also turn into slowest rate. Besides that, our blood pressure falls and body temperature also falls even lower. Our kidney function will be reduced, so we will produce less urine. In this moment, growth hormone will be released. This hormone will help to repair and maintain our immune system and body tissues. Therefore, insufficient deep sleep will affect our health.
In stage 4, it is characterized by rhythmic breathing and limited muscle activity. It occupies 40 percent of our sleep. It is difficult to rouse people from this stage. If we are woken during deep sleep, we cannot adjust ourselves immediately. Therefore, we will feel groggy and disoriented for several minutes.
REM sleep:
This stage will start about 70 to 90 minutes after we fall into deep sleep. Our brain start to active in this stage; sometime it will more active than we are awake. This is the period we dream the most. We will spend at least 2 hours dreaming every night. Sometime we will remember it, but sometime not. We can recall our dream in first few minutes after we wake up, because we can remember our dream from REM sleep, and most REM sleep takes place in the early hours. According to research, women are better than men at remembering their dreams.
From figure 1, we can understand our brain waves are different in every stage of sleep.
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