Ependimal cells produce cerebral spinal fluid. It helps, like he said, make the brain buoyant and washes away toxins. Found that am mic am that they didn't allow to sleep properly had volume changes of their cerebral spinal flood. They had a build up of metabolites overtime. So sleeping allows for you to create new cerebral spinfood and flash away these metabolites. Andit is potentially one of the reasons why, if you don't get enough sleep, you feel groggy,. because you've just accumulated metabolites that haven't beenable to be washed away.