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We've been doing science for a couple thousand years,
我们研究科学已经有几千年了，
so you'd think we'd have most of the nervous system figured out by now.
所以你会认为，我们现在已经知道大部分神经系统了。
Or at least, that we'd know the parts of it, even if we aren't sure what they do.
或者我们至少知道了其中的一部分，即使不确定它们的作用。
Nope. We're still discovering new things all the time.
但事实并非如此。我们一直在发现新事物。
Like, recently, we found a hidden network in the brain called the glymphatic system,
比如最近，我们在大脑中发现了一个叫做胶状淋巴系统的隐藏网络，
whose main job is to clear away waste.
它的主要作用是清除废物。
It operates mostly when you're asleep, might prevent people from developing certain diseases,
它大多数时候在你睡觉时工作，可能会防止人们患上某些疾病，
and has impacted the way we understand how our brains works.
并影响我们理解大脑运作的方式。
Basically, finding it was a pretty awesome surprise.
基本上，它的发现是个相当了不起的惊喜。
Every minute of every day, your cells do all sorts of marvelous things,
你的细胞时时刻刻都会做各种奇妙的事情，
but they also produce waste, like carbon dioxide, water, and larger molecules like proteins.
但它们也会产生废物，比如二氧化碳、水和更大的分子，比如蛋白质。
But that doesn't mean you're, y'know... full of garbage.
但这并不意味着你……满是垃圾。
In most of your body, a network of vessels called the lymphatic system acts like a sewer to clear that junk away.
你身体的大部分有一个叫做淋巴系统的血管网络，它就像下水道一样清除垃圾。
It carries waste to your circulatory system,
它会把废物带到你的循环系统，
where it can then be taken to your liver and kidneys for disposal.
后者可以把废物带到肝脏和肾脏，让它们来处理。
But up until recently, scientists couldn't find anything like that in the brain.
但直到最近，科学家们在大脑中都找不到类似物质。
Even though, relative to other parts of your body, it produces a lot of waste.
尽管，相对于身体的其他部分而言，它会产生大量废物。
Instead, they thought that waste exited the brain by diffusing into the cerebrospinal fluid,
但他们认为废物通过扩散进入脑脊液
or the fluid around your brain and spinal cord.
或者大脑和脊髓周围的液体来排出大脑。
Then it could make its way into the circulatory system.
然后它可以进入循环系统。
For a while, this made sense, since scientists couldn't see any vessels.
有一段时间，这种方法能行得通，因为科学家看不到任何血管。
And that waste had to be going somewhere.
而这些废物必须要去某个地方。
But in 1971, one scientist named Dr. Helen Cserr realized this method wouldn't actually work.
但是在1971年，一位名叫海伦·卡瑟尔的科学家意识到这种方法实际行不通。
She did the math and realized that some of the large proteins in cellular waste would take too long to diffuse.
她通过数学演算意识到，细胞废物中的一些大蛋白质需要很长时间才能扩散。
Still, it wasn't clear where that gunk was going.
不过，它仍没弄明白黏性物质的去向。
And for decades, it was a bit of a head scratcher.
几十年来，这真是件让人头疼的事。
Then, in 2012, we finally figured it out.
直到2012年，我们最终弄明白了。
Scientists at the University of Rochester used a technique called two photon microscopy to look at mouse brains.
罗彻斯特大学的科学家们使用一种“多光子显微技术”来观察老鼠的大脑。
This technique uses lasers to allow scientists to look deep inside live tissues for extended periods of time.
这项技术使用激光，使得科学家们能够长时间观察活体组织内部。
With it, researchers saw that
有了它，研究人员发现
there was an active, directional flow of cerebrospinal fluid into the spaces between brain cells.
活跃的脑脊液定向流入脑细胞之间的空间。
Older fluid was draining out, and it was taking the brain's waste with it.
旧液体正在流失，它正带走大脑的废物。
They called this discovery the glymphatic system,
他们称这个发现为胶状淋巴系统，
and we've since found evidence that it's working in human brains as well.
从那以后，我们发现了它在人类大脑中同样起作用的证据。
Even though we've been studying the brain for a while now,
尽管我们研究大脑已经有一段时间了，
this system was hard to find for a couple of reasons.
但由于几个原因，这个系统很难找到。
One is that, unlike the lymphatic system, the glymphatic system doesn't really have vessels.
一方面，与淋巴系统不同，胶状淋巴系统并没有真正的血管。
So there's not a structure you can find in a dissection.
所以你在解剖中找不到一个结构。
Instead, the fluid flows in the space between blood vessels and the cells that surround them.
相反，液体在血管和环绕它们的细胞之间流动。
It's pretty sneaky.
它鬼鬼祟祟的。
Discovering this system was cool because it means we know more about how our bodies work.
发现这个系统很厉害，因为这意味着我们更了解身体的运作方式了。
But it also might have implications for health and medicine in general.
但它也可能对健康和医学产生影响。
Like, one thing that scientists have learned is that the glymphatic system is almost only turned on when you're sleeping.
比如，科学家们发现一件事，胶状淋巴系统近乎只在你睡觉时打开。
That's because, when you're awake, your body produces elevated amounts of a chemical called norepinephrine.
这是因为你醒着的时候，身体会产生一种叫做去甲肾上腺素的化学物质。
And at least in mice, which have somewhat similar brains to us,
至少在与类似大脑的鼠脑上，
norepinephrine suppresses the glymphatic system.
去甲肾上腺素会抑制胶状淋巴系统。
So, that's one more reason sleep is important for your health, it keeps your brain clean!
所以，这是睡眠对健康很重要的一个原因，它能让大脑保持清洁！
Scientists have also learned that, in mice, the glymphatic system gets less active as they get older.
科学家们也了解到，老鼠随着年龄的增长，胶状淋巴系统变得不那么活跃了。
This probably happens in humans, too, right around the time our risk of dementia is also increasing.
这可能也发生在人类身上，这时，我们患痴呆症的风险也在增加。
This suggests that problems with the glymphatic system
这说明胶状淋巴系统问题
could play a role in dementia and neurodegenerative diseases like Alzheimer's and Parkinson's.
可能在痴呆症和阿尔茨海默氏症与帕金森氏综合症等神经退行性疾病中发挥作用。
These diseases are associated with build-ups of large proteins in the brain,
这些疾病与大脑中累积的大蛋白质有关，
which are some of the junk that the glymphatic system is supposed to clear away.
这些蛋白质是胶状淋巴系统原本要清除的废物。
So understanding how the system works may help scientists figure out better ways
因此，了解系统的工作原理可以帮助科学家找出更好的办法，
to treat these diseases, along with other protein-related conditions.
来治疗这些疾病和其他与蛋白质相关的疾病。
But there's definitely a long way to go.
但肯定还有很长的路要走。
Now, finding the glymphatic system seemed like a huge victory,
现在，发现胶状淋巴系统似乎是个巨大的胜利，
but the surprises weren't quite over yet.
但惊喜还没结束。
Because in 2017, scientists found lymphatic vessels in the human brain, too.
因为在2017年，科学家也在人类大脑中发现了淋巴管。
The ones that weren't supposed to exist.
它们本不应该存在的。
They were hiding in the meninges, the outer membranes that cover the brain and spinal cord.
它们隐藏在脑膜中，脑膜是覆盖大脑和脊髓的外膜。
We didn't know about these vessels before because they're hidden inside a tough membrane.
我们以前不知道这些血管是因为它们隐藏在坚硬的脑膜里。
And they run alongside some pretty prominent blood vessels.
它们和一些相当突出的血管一起运行。
When you're looking at a brain, with an MRI, for example,
比如，当你用核磁共振成像看一个大脑时，
these lymphatic vessels are difficult to see because the blood vessels are in the way.
这些淋巴管很难看到，因为血管挡路。
Kind of like a photobomb.
这有点儿像照片炸弹。
Still, now that we've found all these new systems,
现在，我们既然已经发现了所有这些新系统，
we kind of have more questions than answers.
就会有多余答案的问题。
The next steps are for scientists to figure out how the glymphatic system is involved in human disease,
科学家们接下来要做的是弄清楚胶状淋巴系统如何参与人类疾病的，
and how it and those new lymphatic vessels might work together.
以及它和那些新淋巴管如何一起工作的。
Then, someday, maybe we can use that knowledge to treat disease.
然后总有一天，我们也许可以用这些知识来治疗疾病。
All this goes to show that, even though we're pretty smart,
所有这些都表明，尽管我们很聪明，
we still have a lot to learn about our brains.
但仍有很多要了解大脑的地方。
But the next time someone accuses you of having a dirty mind,
但下次有人指责你有肮脏的想法时，
you can let them know they don't need to worry.
你可以让他们知道他们不需要担心。
Your glymphatic system and those lymphatic vessels, keep your brain sparkling clean!
你的胶状淋巴系统和淋巴管会帮助大脑保持清洁！
Thanks for watching this episode of SciShow Psych, a Complexly production.
感谢您收看本期的心理科学秀，它是一个复杂的成果。
If you'd like to learn even more about your brain's anatomy and the rest of your body,
如果你想更多了解大脑解剖和身体的其他部分，
you can check out Crash Course Anatomy &, Physiology over at youtube.com/crashcourse.
你可以在youtube.com/crashcourse查看速成课程的解剖学和生理学。
