你睡觉时身体干的四件疯狂事

It's a requirement for life, but scientists can't explain why we require sleep. Seriously… they have no idea. What we do know, is that your body starts doing some crazy stuff while you're out.
睡眠是生活的必需，然而科学家们却不能阐明其原因。说实在的，他们毫无头绪。而我们清楚的是：在你熟睡时，你的身体会开始做出一些疯狂的举动。

1. REHEARSE FOR REAL LIFE
1. 预演现实生活

There are more theories for why we dream than there are dreams. However, one pretty interesting theory says your dreams are your brain practicing certain situations to prepare for them happening in real life. Two studies in 2000 in the journal of Behavioral And Brain Sciences proposed a model that the brain uses dreams to see how you react to threatening situations, so you're better prepared in the real world. The theory goes on to say that "genetic memories" that are in our mind from birth contain many of these practice scenarios -- like a "starter pack." Which explains why people often have similar dreams.
解释为何做梦的理论比做的梦都多。然而，一个相当有趣的理论认为：梦境是你的大脑为特定情景在现实中的发生而做的练习。2000年，两个研究刊登在the Journal of Behavioral And Brain Sciences的研究提出了一个模型，认为大脑利用梦境考察你如何应对危机情境，由此在现实生活中你便会准备得更为充分。这个理论还认为，那个自出生起就在我们大脑中的"基因记忆"，包含了许多这些演练方案，它就像一个"启动包"。而这也正解释了为何人们通常拥有相似的梦境。

2. BRAIN WAVES START TO GET EERILY SPECIFIC
2. 脑电波变得异常具体

Neural oscillations, or brain waves, are created by the electrical signals in your brain. Certain waves correlate with certain activities. Scientists are aware of them, and can use them to measure stuff, but have absolutely no clue what purpose they serve. When you sleep however, your neural oscillations become oddly specific for each stage of sleep. Alpha activity, theta waves, delta waves... they all are emitted during very specific points in your sleep cycle. So much so, that scientists can pinpoint the exact part of sleep you're in -- just from the type of brain wave given off.
神经震荡，或脑电波，是由大脑内的电信号产生的。特定的脑电波与特定的活动相关联。科学家们了解这种联系，并能够利用它们判定事物，却毫不清楚它们有什么用途。然而当你熟睡时，神经震荡在睡眠的各个阶段变得异常具体。α行为，θ电波，δ电波……他们全都在睡眠周期中十分具体的点发射。如此，科学家们便可以仅仅通过发射出的脑电波类型，来精确指出你所处的睡眠阶段。

3. BLOOD FLOW TO YOUR HEAD IS RAMPED UP
3. 颅腔血流量增加

Your brain gets more oxygen and nutrients, and you can blame it upon a rush of blood to the head. (No Coldplay fans out there? Really?) Since your brain is one of the only parts of your body that's still fully functioning, what blood is still being pumped gets diverted to your head. This powers all the maintenance functions going on in your skull.
因为一股涌上大脑的血流，你的大脑将获得更多的氧气与营养物质。（这儿没有酷玩乐队的歌迷吧？真的么？）由于睡眠时大脑是身体内唯一满负荷运作的部分，所以仍在被泵出的的血液便转移到了那里。这便为颅腔内所有的维护功能供能。

4. LAST CALL... FOR MONOAMINE NEUROTRANSMITTERS
4. 最后……是单胺类神经递质

The neurotransmitters norepinephrine, serotonin and histamine are kind of like the cocaine, molly, and PCP of your brain -- respectively. They do a lot of important things when you're awake like sharpen your senses, make you feel good, and help regulate the immune system. During REM Sleep, all three of these neurotransmitters are switched off. Your brain is denied access to all three of them in favor of acetylcholine, which activates muscles and movement. The release of acetylcholine is thought to speed up brain waves -- maybe.
去甲肾上腺素、血清素、组胺这些神经递质依次和可卡因、莫利、PCP有些相像。它们在你清醒时起着重要作用，如使感觉更敏锐、提升愉悦感，并且可以帮助调节免疫系统。在快速眼动睡眠过程中，这三种神经递质全部被抑制了。你的大脑拒绝接受这三者，反而更愿意接受乙酰胆碱，它可以活跃肌肉与行为。乙酰胆碱的释放被认为会加速脑电波--但谁也不好说。