11.High School English Listening

When you go back to work or class after lunch, why is it so hard to stay awake?
Although we get energy from food, we also use lots of energy to digest it.
Your energy use increases 25-50% as you digest a meal.
With all that action going on in the digestive system, the body sends extra blood to the gut to supply oxygen and other necessities.
As food enters the stomach, the intestines secrete substances that dilate, or expand, the blood vessels that supply them with blood.
As a result, more blood flows to the upper digestive tract,and there's a bit less to go around to the rest of the body.
That might make your arms and legsand brain feel a little sluggish!
At the same time, the small intestine releases a hormone that activates the part of the brain that controls sleep, making you drowsy.
Finally, the natural components in foods can also contribute tothe snooze effect. Certain foods, especially carbohydrates, increase production of serotonin in the brain.
Serotonin works both to stop sugar craving, and to make you very relaxed.
The larger the meal, the more pronounced that feeling can be.
With all of these physiological reasons why wemight feel sleepy after eating, a siesta after lunch sounds like a brilliant idea, and maybe after dinner and breakfast too!
译文：
当你午饭后回到工作或上课时，为什么很难保持清醒？
虽然我们从食物中获得能量，但我们也使用大量能量来消化食物。
当你消化一餐时，你的能量使用增加了25-50%。
随着消化系统中的所有行动，身体向肠道发送额外的血液以供应氧气和其他必需品。
当食物进入胃部时，肠道分泌的物质会扩张，或扩大为其提供血液的血管。
因此，更多的血液流向上消化道，而流向身体其他部位的血液就少了一点。
这可能会使你的手脚和大脑感觉有点迟钝!
同时，小肠会释放一种激素，激活大脑中控制睡眠的部分，使你昏昏欲睡。
最后，食物中的天然成分也能促成打盹效果。某些食物，特别是碳水化合物，会增加大脑中血清素的分泌。
血清素既能阻止对糖的渴望，又能使你非常放松。
饭量越大，这种感觉就越明显。
有了所有这些吃完饭后可能感到困倦的生理原因，午餐后的午睡听起来是一个绝妙的主意，也许晚餐和早餐后也是如此
重点词汇：
go back to 恢复 ; 重新开始 ; 重操 ; 回到
With all 尽管
digestive system 消化系统
blood vessels 血管 ; blood vessel的复数
As a result 因此
digestive tract 消化道
go around 造访 ; 拜访 ; 经常做 ; 习惯打扮成 ; 流传，传播 ; 都能分到 ; 够每人一份
a little 一点