The Sleep Cycle

Hi/salam.

Today i'm going to tell all of you about the sleep cycle. I bet not many of you know about sleep cycle despite doing it's act every time you fall asleep. You spent 30% of your life in order to sleep and i think it's important for you to know the sleep cycle. If not, why do you spend 6-8 hours a day to sleep, right?

Alright. Sleep cycle consists of two parts, first is the non-rapid eye movement or simply NREM stage and next is rapid eye movement or REM stage. The NREM stage is further divided into four sub-stages which we called, stage 1, stage 2 and stage 3. During the early days, scientist believed that there are actually 4 stages, but in modern days, stage 3 and stage 4 is combined. That's how we got only 3 stages. The cycle begins the moment you fall asleep.

STAGE 1

this is the first stage. If someone falls into this stage, they will loose awareness of the surrounding but also felt as he/she actually never falls asleep. This is the stage if you see your friends sleep in class while the lecturer is teaching. The trademark of this stage is the hypnic jerk. People experience the hypnic jerk will tell you that they have the sensation of falling/being shot, anything that cause them to die or hurt very bad. After spending 5 to 15 minutes in this stage, we will now move in stage 2.

STAGE 2

During this stage, the alpha wave is replaced by the theta waves. If you monitor the sleep under the electroencephalogram, you will see "sleep spindles" and "K-complexes" signature. Basically these 2 things act as guardian to you. They will monitor the stimuli that we have while we are sleeping. If, the stimuli is consider dangerous, these two things will send a signal to your brain and you will suddenly wake up. For example, if you usually sleep with the light off, if you are in stage 2 and someone switch the light on, you will immediately wake up because it is categorized as dangerous.

STAGE 3

During this stage, the theta waves is replaced by delta waves, which indicates that the body is ready to enter stage deep sleep stage. Delta waves is a slow wave movement and that is also why this stage is sometimes refer to as slow wave sleep. During this stage, the body will totally become unaware of to what is happening on the surrounding. And if the body is forced to wake up during this stage, you will notice that the person will become very grumpy, mumbles a little bit and then continue with his/her sleep. So beware if you try to wake someone during this stage, you might consider bring some back up. XD

REM Stage.

After about an hour in NREM stage, the body will enter REM stage. During this stage, the delta wave is replaced back by the alpha wave. As I mentioned, alpha wave is the wave that occurs when your brain is active. That is why during this stage, most people will remember their dreams, which scientists believe as a result that occurs because your brain tries to sort all the information that we had during the day. REM stage occurs around 30 minutes for the first sleep cycle and continue to increase in time throughout the whole sleeping process.

The total time taken for one complete cycle to occurs is around one and a half hour. So in 6-8 hours sleep will have around 4 to 5 cycles. The cycle is also affected by the circadian rhythm, our activity during the day, eating habit and some other factor. And the cycles vary from one person and another but the one i mention here is the usual thing that happen. I do hope you manage your sleep well as good and fresh start in the morning helps you to get into the mood. That's all, thanks for reading.