Scientists believe they have discovered a new reason why we need to sleep - it replenishes a type of brain cell.
Sleep ramps up the production of cells that go on to make an insulating material known as myelin which protects our brain's circuitry.
http://www.bbc.co.uk/news/health-23932577
Sleep ramps up the production of cells that go on to make an insulating material known as myelin which protects our brain's circuitry.

http://www.bbc.co.uk/news/health-23932577