2020年初三英语中考复习 阅读指导课 有效使用阅读策略Skimming和Scanning （共29张PPT）+学案 无答案

The Mystery of Sleep It might seem like sleep is a big waste of time. But scientists know it isn’t. While you’re sleeping quietly in your bed, there are many things going on in your brain and body. The Stages of Sleep Every night, you go through more than one cycle of sleep, and each cycle is made of five different stages. When you begin to fall asleep, your body enters Stage 1. You are still very close to being awake, but your brain begins to work more slowly. Your body relaxes. After several minutes, you go into Stage 2. You are still easy to wake up, but you would know you are sleeping. Then you fall deeply asleep into Stage 3. Your heart slows down, and you breathe more slowly, too. Noises nearby would probably not wake you up. Finally, you go into Stage 4. Now you are in very deep sleep and it’s hard to wake you up. You will stay in Stage 4 for almost 20 minutes, which is the longest period of deep sleep you’ll have all night. After that, you slowly move back to Stages 3 and 2 again. And then your sleep gets really interesting. As you come back through Stage 2, you go into Stage 5. In Stage 5, your eyes move quickly back and forth behind your closed eyelids (眼皮). Your brain becomes much more active, almost as active as when you’re awake. While your eyes are moving from side to side, a detailed story is running through your head. That is when you’re dreaming.  After Stage 5, the cycle starts over again from Stage 1. Going Without Sleep Missing sleep can make you weaker than you were the day before. If you miss just 2 hours of sleep, you will feel slow the next day. You will not think as fast as usual. If you miss a whole night’s sleep you will feel worried and unhappy. Your body’s muscles heal (痊愈) and grow stronger during your sleep. If you get sick, you need your sleep to get better. You heal while you are sleeping. That’s when your body makes more chemicals (化学物质) that help create new skin, muscles and other parts of your body.  Sleep On It Scientists stil