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We've been doing science for a couple thousand years,
我們研究科學已經有幾千年了，
so you'd think we'd have most of the nervous system figured out by now.
所以你會認為，我們現在已經知道大部分神經系統了。
Or at least, that we'd know the parts of it, even if we aren't sure what they do.
或者我們至少知道了其中的一部分，即使不確定它們的作用。
Nope. We're still discovering new things all the time.
但事實并非如此。我們一直在發現新事物。
Like, recently, we found a hidden network in the brain called the glymphatic system,
比如最近，我們在大腦中發現了一個叫做膠狀淋巴系統的隱藏網絡，
whose main job is to clear away waste.
它的主要作用是清除廢物。
It operates mostly when you're asleep, might prevent people from developing certain diseases,
它大多數時候在你睡覺時工作，可能會防止人們患上某些疾病，
and has impacted the way we understand how our brains works.
并影響我們理解大腦運作的方式。
Basically, finding it was a pretty awesome surprise.
基本上，它的發現是個相當了不起的驚喜。
Every minute of every day, your cells do all sorts of marvelous things,
你的細胞時時刻刻都會做各種奇妙的事情，
but they also produce waste, like carbon dioxide, water, and larger molecules like proteins.
但它們也會產生廢物，比如二氧化碳、水和更大的分子，比如蛋白質。
But that doesn't mean you're, y'know... full of garbage.
但這并不意味著你……滿是垃圾。
In most of your body, a network of vessels called the lymphatic system acts like a sewer to clear that junk away.
你身體的大部分有一個叫做淋巴系統的血管網絡，它就像下水道一樣清除垃圾。
It carries waste to your circulatory system,
它會把廢物帶到你的循環系統，
where it can then be taken to your liver and kidneys for disposal.
后者可以把廢物帶到肝臟和腎臟，讓它們來處理。
But up until recently, scientists couldn't find anything like that in the brain.
但直到最近，科學家們在大腦中都找不到類似物質。
Even though, relative to other parts of your body, it produces a lot of waste.
盡管，相對于身體的其他部分而言，它會產生大量廢物。
Instead, they thought that waste exited the brain by diffusing into the cerebrospinal fluid,
但他們認為廢物通過擴散進入腦脊液
or the fluid around your brain and spinal cord.
或者大腦和脊髓周圍的液體來排出大腦。
Then it could make its way into the circulatory system.
然后它可以進入循環系統。
For a while, this made sense, since scientists couldn't see any vessels.
有一段時間，這種方法能行得通，因為科學家看不到任何血管。
And that waste had to be going somewhere.
而這些廢物必須要去某個地方。
But in 1971, one scientist named Dr. Helen Cserr realized this method wouldn't actually work.
但是在1971年，一位名叫海倫·卡瑟爾的科學家意識到這種方法實際行不通。
She did the math and realized that some of the large proteins in cellular waste would take too long to diffuse.
她通過數學演算意識到，細胞廢物中的一些大蛋白質需要很長時間才能擴散。
Still, it wasn't clear where that gunk was going.
不過，它仍沒弄明白黏性物質的去向。
And for decades, it was a bit of a head scratcher.
幾十年來，這真是件讓人頭疼的事。
Then, in 2012, we finally figured it out.
直到2012年，我們最終弄明白了。
Scientists at the University of Rochester used a technique called two photon microscopy to look at mouse brains.
羅徹斯特大學的科學家們使用一種“多光子顯微技術”來觀察老鼠的大腦。
This technique uses lasers to allow scientists to look deep inside live tissues for extended periods of time.
這項技術使用激光，使得科學家們能夠長時間觀察活體組織內部。
With it, researchers saw that
有了它，研究人員發現
there was an active, directional flow of cerebrospinal fluid into the spaces between brain cells.
活躍的腦脊液定向流入腦細胞之間的空間。
Older fluid was draining out, and it was taking the brain's waste with it.
舊液體正在流失，它正帶走大腦的廢物。
They called this discovery the glymphatic system,
他們稱這個發現為膠狀淋巴系統，
and we've since found evidence that it's working in human brains as well.
從那以后，我們發現了它在人類大腦中同樣起作用的證據。
Even though we've been studying the brain for a while now,
盡管我們研究大腦已經有一段時間了，
this system was hard to find for a couple of reasons.
但由于幾個原因，這個系統很難找到。
One is that, unlike the lymphatic system, the glymphatic system doesn't really have vessels.
一方面，與淋巴系統不同，膠狀淋巴系統并沒有真正的血管。
So there's not a structure you can find in a dissection.
所以你在解剖中找不到一個結構。
Instead, the fluid flows in the space between blood vessels and the cells that surround them.
相反，液體在血管和環繞它們的細胞之間流動。
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.
發現這個系統很厲害，因為這意味著我們更了解身體的運作方式了。
But it also might have implications for health and medicine in general.
但它也可能對健康和醫學產生影響。
Like, one thing that scientists have learned is that the glymphatic system is almost only turned on when you're sleeping.
比如，科學家們發現一件事，膠狀淋巴系統近乎只在你睡覺時打開。
That's because, when you're awake, your body produces elevated amounts of a chemical called norepinephrine.
這是因為你醒著的時候，身體會產生一種叫做去甲腎上腺素的化學物質。
And at least in mice, which have somewhat similar brains to us,
至少在與類似大腦的鼠腦上，
norepinephrine suppresses the glymphatic system.
去甲腎上腺素會抑制膠狀淋巴系統。
So, that's one more reason sleep is important for your health, it keeps your brain clean!
所以，這是睡眠對健康很重要的一個原因，它能讓大腦保持清潔！
Scientists have also learned that, in mice, the glymphatic system gets less active as they get older.
科學家們也了解到，老鼠隨著年齡的增長，膠狀淋巴系統變得不那么活躍了。
This probably happens in humans, too, right around the time our risk of dementia is also increasing.
這可能也發生在人類身上，這時，我們患癡呆癥的風險也在增加。
This suggests that problems with the glymphatic system
這說明膠狀淋巴系統問題
could play a role in dementia and neurodegenerative diseases like Alzheimer's and Parkinson's.
可能在癡呆癥和阿爾茨海默氏癥與帕金森氏綜合癥等神經退行性疾病中發揮作用。
These diseases are associated with build-ups of large proteins in the brain,
這些疾病與大腦中累積的大蛋白質有關，
which are some of the junk that the glymphatic system is supposed to clear away.
這些蛋白質是膠狀淋巴系統原本要清除的廢物。
So understanding how the system works may help scientists figure out better ways
因此，了解系統的工作原理可以幫助科學家找出更好的辦法，
to treat these diseases, along with other protein-related conditions.
來治療這些疾病和其他與蛋白質相關的疾病。
But there's definitely a long way to go.
但肯定還有很長的路要走。
Now, finding the glymphatic system seemed like a huge victory,
現在，發現膠狀淋巴系統似乎是個巨大的勝利，
but the surprises weren't quite over yet.
但驚喜還沒結束。
Because in 2017, scientists found lymphatic vessels in the human brain, too.
因為在2017年，科學家也在人類大腦中發現了淋巴管。
The ones that weren't supposed to exist.
它們本不應該存在的。
They were hiding in the meninges, the outer membranes that cover the brain and spinal cord.
它們隱藏在腦膜中，腦膜是覆蓋大腦和脊髓的外膜。
We didn't know about these vessels before because they're hidden inside a tough membrane.
我們以前不知道這些血管是因為它們隱藏在堅硬的腦膜里。
And they run alongside some pretty prominent blood vessels.
它們和一些相當突出的血管一起運行。
When you're looking at a brain, with an MRI, for example,
比如，當你用核磁共振成像看一個大腦時，
these lymphatic vessels are difficult to see because the blood vessels are in the way.
這些淋巴管很難看到，因為血管擋路。
Kind of like a photobomb.
這有點兒像照片炸彈。
Still, now that we've found all these new systems,
現在，我們既然已經發現了所有這些新系統，
we kind of have more questions than answers.
就會有多余答案的問題。
The next steps are for scientists to figure out how the glymphatic system is involved in human disease,
科學家們接下來要做的是弄清楚膠狀淋巴系統如何參與人類疾病的，
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.
然后總有一天，我們也許可以用這些知識來治療疾病。
All this goes to show that, even though we're pretty smart,
所有這些都表明，盡管我們很聰明，
we still have a lot to learn about our brains.
但仍有很多要了解大腦的地方。
But the next time someone accuses you of having a dirty mind,
但下次有人指責你有骯臟的想法時，
you can let them know they don't need to worry.
你可以讓他們知道他們不需要擔心。
Your glymphatic system and those lymphatic vessels, keep your brain sparkling clean!
你的膠狀淋巴系統和淋巴管會幫助大腦保持清潔！
Thanks for watching this episode of SciShow Psych, a Complexly production.
感謝您收看本期的心理科學秀，它是一個復雜的成果。
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腦解剖和身體的其他部分，
you can check out Crash Course Anatomy &, Physiology over at youtube.com/crashcourse.
你可以在youtube.com/crashcourse查看速成課程的解剖學和生理學。
