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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 gut2 to supply oxygen and other necessities.
How does the body know when to do this?
As food enters the stomach, the intestines4 secrete5 substances that dilate6, or expand, the blood vessels7 that supply them with blood. As a result, more blood flows to the upper digestive tract8, and there’s a bit less to go around to the rest of the body. That might make your arms and legs and brain feel a little sluggish9!
At the same time, the small intestine3 releases a hormone10 that activates11 the part of the brain that controls sleep, making you drowsy12. Finally, the natural components13 in foods can also contribute to the snooze effect. Certain foods, especially carbohydrates14, increase production of serotonin in the brain. Serotonin works both to stop sugar craving15, and to make you very relaxed. The larger the meal, the more pronounced that feeling can be. With all of these physiological16 reasons why we might feel sleepy after eating, a siesta after lunch sounds like a brilliant idea, and maybe after dinner and breakfast too!
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1 siesta | |
n.午睡 | |
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2 gut | |
n.[pl.]胆量;内脏;adj.本能的;vt.取出内脏 | |
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3 intestine | |
adj.内部的;国内的;n.肠 | |
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4 intestines | |
n.肠( intestine的名词复数 ) | |
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5 secrete | |
vt.分泌;隐匿,使隐秘 | |
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6 dilate | |
vt.使膨胀,使扩大 | |
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7 vessels | |
n.血管( vessel的名词复数 );船;容器;(具有特殊品质或接受特殊品质的)人 | |
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8 tract | |
n.传单,小册子,大片(土地或森林) | |
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9 sluggish | |
adj.懒惰的,迟钝的,无精打采的 | |
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10 hormone | |
n.荷尔蒙,激素,内分泌 | |
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11 activates | |
使活动,起动,触发( activate的第三人称单数 ) | |
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12 drowsy | |
adj.昏昏欲睡的,令人发困的 | |
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13 components | |
(机器、设备等的)构成要素,零件,成分; 成分( component的名词复数 ); [物理化学]组分; [数学]分量; (混合物的)组成部分 | |
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14 carbohydrates | |
n.碳水化合物,糖类( carbohydrate的名词复数 );淀粉质或糖类食物 | |
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15 craving | |
n.渴望,热望 | |
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16 physiological | |
adj.生理学的,生理学上的 | |
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