1 When we fall asleep, our brain goes into "low energy" mode

2 sleep is divided into two main states: non-REM and REM

3 A newborn baby will sleep up to 19 hours a day, school pupil usually needs around 11 hours sleep,teenagers needs up to ten hours and adult generally needs around eight hours a night.

4. narcolepsy is a condition where a person can become incredibly sleepy with very little warning