Summary "Sleep and dreams"

Sleep is a reversible condition of reduced responsiveness usually associated with immobility, it is busy time to brain.

Sleep is divided in 4 different stages .The first one is the beginning of sleep and the fourth is the deepest stage of sleep. While sleep people fall in all this stage, sometimes repeatedly.

Another part of sleep is REM( rapid eye movement. Physiologically, certain neurons in the brain stem are particularly active during REM sleep, and are probably responsible for its occurrence.

There are some illnesses of sleep, for example, Insomnia, REM sleep behavior and etc., luckily these illnesses can be cured by drugs with no harm eventually.

To conclude, sleeping and dreaming is one of the most important thing for creatures, so disorders related with sleep must be analyzed as much as possible.