Sleep is a condition of body and mind that typically recurs for several hours every night, in which the eyes are closed, the postural muscles relaxed, and the activity of the brain altered, and the consciousness of the surrounding practically suspended.
Sleep isn’t just lost time or just a way to rest when our important work is done. Instead, it is a critical function in which our body balances and regulates its vital systems, affecting respiration and regulating everything from circulation to growth and immune response.
Sleep is also crucial to our brain, with a fifth of our body’s circulatory blood being connected to it as we drift off. What goes on in our brain when we sleep is an intensely period of reconstructing that is crucial to our memories.