9781422273890

of a hormone called melatonin, which makes the person gradually begin to feel sleepy. The innate nature of the circadian rhythm explains why “jet lag” exists. Let’s say you take a flight from Boston to San Francisco. In that case, your internal clock will be running three hours ahead of the body clock of the person who picks you up at the airport. Fortunately, your circadian rhythm can adjust to changes in the environment; it may take a day or two, but your Boston-based body clock will get used to the new time zone. People who’ve experienced physical damage

Understanding Sleep

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