Why do we have to sleep?

No one is sure to have the right explanation. Of course, sleep rests the body, new cells are formed, the tissues are repaired.
But during sleep, the brain is very active. Some think that it sorts the events of the day, classifies the new information and organizes them with those already recorded.
This work can be used to learn from new experiences.
A newborn needs 16 hours of sleep a day, at 65 years 6 hours is enough. The areas of the brain that control movement and language remain awake: we can talk, sit and even walk in sleep, no one knows why we do it, and we do not remember when we wake up.

• We sleep, on average, 8 hours a day,  20 years in a lifetime!
• During sleep the heart rate is slowed down.
• Sleep consists of 4 or 5 cycles, which last from 60 to 100 minutes.
• They start with slow sleep and end with REM sleep.(Rapid Eye Movement)
• In adults, slow sleep accounts for about 80% of total sleep.
• Growth hormone is secreted during slow sleep.
• We dream mostly during REM sleep.
• We sleep more when we are sick because our body needs rest to get better.