Step 1: What is sleep?
Being asleep means you are effectively unconscious to the sensory world. That means you won't hear, feel, taste, or smell, and you wouldn't even see if your eyes were pulled open but if one or more stimulus is strong enough it will wake you.
You will experience 5 stages of sleep in recurring cycles of around 90 to 110 minutes.
Step 2: Stage one
Your stage one sleep cycle lasts around 10 minutes. Your body becomes more drowsy, your eyes shut but you will still be acutely aware of our surroundings. You can be woken easily during this stage and if you are then you'll feel like you've had no rest at all. Your body activity reduces by 50% at this early stage.
During this stage, many people experience sudden muscle contractions or a sensation of falling.
This gets the body ready for deeper sleep activity
Step 3: Stage two
Stage 2 lasts about 15 minutes, your eye movement all but stops and your brain waves become much slower called theta waves. Your muscles will tense and relax intermittently, which might make you twitch slightly. Your body temperature will also fall.
You are now ready for deeper sleep.
Step 4: Stages three and four
The third and fourth stages of sleep are known as deep sleep time or delta sleep. Breathing and heart rates reach their lowest levels and the brain starts to produce large slow waves known as delta waves. It's very difficult to be woken from deep sleep.
The brain produces slow delta waves almost exclusively and there will be no eye movement or muscle activity.
At this stage your glands secrete large amounts of growth hormones, and as a result helps restore your body from the wear and tear of daily activity.
This is when you may experience sleep walking or night terrors, and in the case of small children, bedwetting.
Stages 2 and 3 are repeated before the brain moves onto the final stage of sleep, REM.
Step 5: Stage five
Rapid eye movement or REM sleep is referred to as such because this is when you dream, so your eyes respond by moving rapidly beneath closed eyelids. Physically your breathing and blood pressure rise, although effectively your body is paralyzed from the neck down. This is said to be a way our bodies stop us from acting out our dreams.
There is much speculation as to the benefits of REM sleep, but there is strong evidence suggesting this is when you'll sort through all the information you picked up in the day. Your brain discards unnecessary information and consolidates all your new memories.
You will move into REM state around 70 to 90 minutes after going to sleep, and you'll return to this stage another 3 to 5 times during the night.
REM sleep completes your sleeping cycle before the whole process starts again.