LecturerGood morning. We spend a third of our lives asleep, yet most of us understand it poorly. Today I'll explain what actually happens when we sleep, and how to do it better.
LecturerFirst, sleep is not one continuous state at all. It runs in repeating cycles right through the night.
LecturerEach full cycle lasts roughly ninety minutes, and a healthy sleeper goes through four or five of them.
LecturerDuring the deepest stage, the body repairs itself — muscles, tissues and the immune system are all quietly restored.
LecturerDreaming, by contrast, happens mainly in what we call REM sleep, which turns out to be vital for fixing memories.
LecturerBut what makes us feel drowsy in the first place? A hormone called melatonin, which the brain releases as it gets dark.
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