题型：阅读理解 题类：常考题 难易度：普通
安徽省蚌埠市第二中学2017-2018学年高二上学期英语8月月考试卷
Try this: For an entire day, forget about the clock. Eat when you're hungry and sleep when you're tired. What do you think will happen?
You may be surprised to find that your day is much like most other days. You'll probably get hungry when you normally eat and tired when you normally sleep. Even though you don't know what time it is, your body does.
These patterns of daily life are called circadian rhythms（生理节奏）, and they are more than just habits. Inside our bodies are several clocklike systems that follow a roughly 24-hour cycle. Throughout the day and night, our inner clocks direct changes in temperature, body chemicals, hunger, sleepiness and more.
Everyone's rhythms are different, which is why you might like to stay up late while your sister always wants to go to bed early. But on the whole, everyone is programmed to fell tired at night and energetic during the day.
Learning about our body clocks may help scientists understand why problems arise when we act out of step with our circadian rhythms. For example, traveling across time zones can make people wake up in the middle of the night. Regularly staying up late can make kids do worse in tests.
"There is a growing sense that when we eat and when we sleep are important parts of how healthy we are," says Steven Shea, director of the Sleep Disorders Program at Brigham and Women's Hospital in Boston.
One way to learn about how our body clocks tick is to mess them up and see what happens. That's what neurologist（神经病学家）Frank Scheer and his workmates did in a recent study.
Staying up night after night, their studies suggest, could make kids extra hungry and more likely to gain weight. And regularly sleeping too little, Scheer says, may be one cause of the recent increase in childhood obesity.
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