Let me know if this sounds familiar.
你是否有这样的经历
You’re texting someone,
你正给一个人发信息
nothing all that timely or important.
不需要及时回复 也不是那么重要
You’re just having a friendly chat about your day at work,
你只是随便聊聊今天的工作
catching them up on some office gossip.
聊一聊办公室八卦
While you’re texting, you check social media
聊天之余 你翻看社交媒体
see that the friend you are texting with
看到你正聊天的朋友
posted a video of their new baby
发布了一个他们小孩的视频
and it’s adorable.
非常可爱
So you send them a message through that social media app.
于是你又在这个社交软件上给他发了消息
Now you’re in a pickle.
这下你就尴尬了
For us overthinkers, this is a nightmare.
对容易想多的人而言 这是噩梦
Do you acknowledge that you’re having
你意识到你正用两个
two separate conversations through two different apps?
不同的软件进行单独的对话吗？
Do you keep on living this double life
你是否继续过着这种双重生活
where two different realities of yourself exist
在某种薛定谔式的短信对话中
in a kind of shrodinger’s text message conversation?
存在两个不同现实世界的自己？
Do you do the unthinkable and call that person on the phone?
你会做难以置信的事 给那个人打电话吗？
This is what our cells are trying to juggle at a much bigger level,
这就是我们体内的细胞要应付之事的宏观版本
but without the added pressure of social contracts.
只不过细胞不需要考虑人情世故
You don’t have just two different conversations happening in two different apps.
你不仅是在用两个不同的社交软件聊天
You have trillions of conversations happening
你体内也有数以亿计的交流
between cells or within cells,
在细胞间或细胞内发生
both between cells right next to each other
可以是相邻细胞间的交流
and between cells over a meter apart.
也可以相距一米以外的细胞间的交流
And it’s not just the number of messages,
这种交流不仅基于信息数量
but the mode of messaging.
也基于信息传递方式
So in today’s video,
所以在今天的视频中
we’re going to learn what exactly is a cellular message,
我们将了解到底什么是细胞信号
and how cells get messages from point A to point B.
以及细胞如何从A点到B点获得信息
Because I hate to break it to you,
我本来不想告诉你
but cells don’t use emoji.
但细胞不使用表情符号
In order to communicate, you have to have some kind of language.
为了交流 你必须掌握某类语言
And while I’ve personally had conversations in a language composed entirely of Nicholas Cage gifs,
虽然我个人完全能用尼古拉斯•凯奇的表情包进行交流
your cells aren’t quite as sophisticated.
但你体内的细胞用起来没那么熟练
I know what you’re thinking,
我知道你在想什么
that is clearly a man of exquisite taste and culture
他是一个既有品位又有文化的人
and I agree.
我完全同意
Your cells, on the other hand, speak a language of chemicals.
另一方面 细胞用的是化学语言
The message they send out is a chemical called a ligand.
细胞释放的信息是一种叫配体的化学物质
These ligands come in all shapes and sizes,
配体的形状和大小多样
calling something a ligand just means it’s a molecule that binds to a receptor,
配体就是能与受体结合的分子
and receptors are exactly what they sound like.
受体就是字面意思所表示的那样
Some kind of protein built to receive a particular ligand.
某种合成的蛋白质只能接受特定的配体
These things can be on the outside of the cell or within a cell,
受体可以存在于细胞外或细胞内
and as you can imagine,
可想而知
there’s a time and place to use different ligands and receptors.
不同的情况会使用不同的配体与受体
Like we mentioned in our hormone episode,
就像讲激素那一期提到的
some chemicals like steroids can cross the cell membrane
一些化学物质像类固醇能穿过细胞膜
and bind to receptors inside the cell.
与细胞内的受体结合
But other protein-based hormones can’t pass through the membrane,
但其他蛋白质类激素不能穿过细胞膜
but they can bind to receptors on the surface of the cell,
只能与细胞表面的受体结合
and communicate their message that way.
并且用这种方式交流信息
Once the ligand binds to a receptor,
一旦配体与受体结合
the chemical messages get interpreted
化学信号就被解读
and any number of biological reactions can happen.
然后引发一系列的生物反应
Cellular processes can start or speed up or slow down,
最终启动 加速或减慢细胞活动
often leading to complex chains of events
这常导致复杂的级联反应
that make up the important processes in our biology.
级联反应组成了生物体的重要活动过程
But in this video we’re focusing on
但本期视频 我们主要学习
how messages are spoken and heard,
信息如何发送和接收
not what the cells do with that information.
而不是细胞对信息做出什么反应
Right off the bat,
一开始
when we’re looking at the different ways cells communicate,
当我们了解到细胞通讯的不同方式时
we care about the distance that the ligand has to travel.
我们要关注配体移动的距离
Just like when you communicate with your friends,
就像当你与朋友交流时
some modes of communication are built for different situations.
针对不同情景会有不同的交流方式
In some cases, cells can be in direct contact
一些情况下 细胞间直接接触
and pass ligands straight to each other.
并直接将配体传给对方
It’s especially useful
这样效率很高
when you want to pass tiny particles like Calcium and other ions
当你想传递很小的粒子到邻近细胞时
through to neighboring cells.
比如钙离子和其他的离子
In this case, Calcium is the ligand
这种情况下 钙离子是配体
that’s sent off to a receptor in the neighboring cell.
它会被送至邻近细胞的受体处
Not surprisingly, this method is called direct signaling,
毫无疑问 这种方式就叫直接联系
and we can see it in action in the electrical activity of the heart muscle.
我们可以看到它在心肌电活动中起作用
As a general rule, you want your heart muscle to contract in sync with other parts of the heart muscle,
通常 我们希望所有心肌同步收缩
and to do that,
要做到这一点
your heart needs to transmit an electrical signal across itself extremely quickly.
你的心脏自身需要非常快速地传递电信号
So the heart has little proteins between each cardiac muscle
因此心脏各心肌间有很小的连接蛋白
called gap junctions,
这叫做间隙连接
that let ions pass through super fast.
这可使离子快速通过
It’s basically a direct connection
这基本上就是一种
from the inside of one cell to another
两个细胞内部的直接联系
that’s only big enough for every tiny particles.
这种连接只能让非常微小的粒子通过
This makes for a faster and more coordinated contraction,
这使心肌收缩一致且更快
ultimately allowing for a normal heart beat.
最终实现正常的心跳
But eventually our cells have to start talking with other types of cells,
但最终细胞要完成与其他类型细胞的通讯
which is what the next type of direct signaling does well.
就要依靠下一类直接信号的作用
Almost all of our cells have proteins on their surfaces,
几乎所有细胞表面都有蛋白质
and other cells can have complementary matching proteins on their surfaces,
其他细胞表面有与其匹配的蛋白质复合物
like a lock and key.
就像锁与钥匙
When those proteins match up to proteins on other cells,
当不同细胞表面的蛋白相互匹配时
they create some kind of reaction and pass on the signal.
它们会做出某些反应并传递信号
Think about it like passing notes in class.
就像上课传纸条一样
You could write a note, crumple it up,
你可以写一个纸条 将它揉成一团
and kick it across the ground to your friend,
然后从地上踢给你朋友
or you could just hand it off.
你也可以把纸条直接递给朋友
This is a fool-proof note passing strategy,
这是种十分安全的传纸条方式
trust me, I was a junior high teacher.
相信我 因为我曾是一名初中教师
This type of cell communications
这种类型的细胞通讯
is how our immune systems
是我们体内免疫系统
distinguish healthy cells from foreign invaders.
区分健康细胞与外来入侵细胞的方法
Our healthy cells have a protein on its surface
我们体内健康细胞表面有一种
called major histocompatibility complex 1,
叫主要组织相容性复合体1
or MHC class 1 for short.
简称MHC1的蛋白质
And immune cells called Natural Killer cells
一种叫做自然杀伤细胞的免疫细胞
have proteins on their surface that temporarily bind to these MHC class 1 proteins.
表面有能暂时结合MHC1类蛋白的蛋白质
In this case, the Natural Killer displays a receptor,
这种情况下 自然杀伤细胞是受体
and the MHC class 1 is the ligand.
MHC1类分子是配体
When that happens,
当两者识别后
the cell is identified as part of your own body
这一细胞被确认是你体内的一部分
and the Natural Killer cell leaves it alone.
自然杀伤细胞就会放过它
But when our cells are infected by viruses,
但当细胞被病毒感染时
say the chickenpox or herpes virus,
如水痘或疱疹病毒
those MHC class 1s don’t get displayed anymore,
MHC1类分子不再表达
and the Natural Killer cell destroys it.
自然杀伤细胞就会裂解受感染细胞
It’s the ultimate version of not knowing the secret password.
这就是不知道密码的终极结局
You don’t have MHC?
你没有MHC？
Ohh, I guess you’re gonna die then.
噢 我猜你会死的
Now, the cardiac gap junction and the Natural Killer cell examples
心脏的间隙连接和自然杀伤细胞
both depend on the cells touching each other.
都是需要细胞间互相接触的例子
But what if you wanted to talk to cells a little farther away?
但如果想与比较远的的细胞通讯呢？
Well, it depends on how far away.
那取决于有多远
If you want to communicate with cells in the nearby,
如果是与附近的细胞交流
and just the nearby— vicinity,
就只是在邻近的细胞之间
that’s where paracrine signaling comes in handy.
旁分泌信号就派上用场了
In this type of signaling,
在这类的细胞信号中
a cell will release a wave of ligands to the liquid around itself,
细胞会释放配体到它周围的组织液中
and potentially they run into receptors for that ligand.
它们可能会遇到相匹配的受体
If not, the ligand doesn’t exert an effect and gets broken down.
如果没有的话 配体不会起作用然后被降解
You can see this in action whenever you get a cut.
当你被割伤时就会看到这一效应
When something disrupts the endothelium,
当血管内部的薄层上皮细胞
that thin layer of epithelial cells on the inside of a blood vessel,
也就是内皮细胞被破坏时
it releases chemicals into the bloodstream around it.
它会向周围的血液中释放一些化学物质
Those chemicals kick off a series of biological reactions
这些化学物质会引发一系列生物反应
that recruits platelets to the scene of the injury.
从而使血小板聚集于伤口处
Those platelets stick together with other connective tissue on top of the injury
血小板与其他结缔组织聚集在伤口表面
and provide the first steps to healing that cut.
开始伤口愈合的第一步
This is a great use of paracrine signaling,
这就是旁分泌信号的伟大之处
since you only want the ligand to affect cells in the nearby area.
因为你只想让配体作用于周围的细胞
It would be bad news if all the platelets in your blood suddenly clumped together.
如果血液里的血小板突然全部聚集 这会很糟
So paracrine signaling is a good way of communicating with nearby cells,
所以旁分泌是和周围细胞通讯的好方法
but they can use some of the same mechanisms to talk to themselves.
但它们也可以通过一些相同的机制与自身通讯
It’s called autocrine signaling—
这就是自分泌信号
a cell releases a ligand lands on a receptor it has on its own surface.
细胞释放配体并与自身表面的受体结合
It’s like writing yourself a message on a sticky note in the morning
这就像早上给自己写了个便条
and reading it at noon.
然后中午看了它
We see this in a few different places,
我们在几个不同的地方看到自分泌信号
mainly when it comes to tissues that are growing or differentiating
主要是在正在生长和分化的组织中
like when we’re developing in the womb.
例如在子宫中发育的胚胎
For instance, epithelial cells secrete a ligand called epithelial growth factor
例如上皮细胞会分泌一种叫表皮生长因子
that stimulates them to grow.
可以促进细胞生长的配体
But not every cell is cut out for autocrine signaling.
但不是每个细胞都适合自分泌信号
This type of communication relies on the cell having a lot of receptors on its surface
这种通讯方式需要细胞表面有大量的受体
that readily bind to that ligand
来与配体结合
which makes them more likely to hear the message they just sent out.
使细胞更容易接收自身发出的信息
We have one final way of communicating around the body,
最后要讲的一种体内细胞通讯方式
and it involves my favorite chemicals— hormones.
它涉及到我最喜欢的化学物质——激素
Endocrine signaling is what our endocrine system does,
内分泌信号是由内分泌系统分泌的
pumps hormones into the bloodstreamm
并把激素泵到血液中
so it can land on a cell somewhere else in the body
这样它就能随血液到达身体其他部位的细胞
and have its effect.
并发挥作用
Compared to all the other forms of communication,
与其他细胞通讯方式相比较
endocrine signaling is slow
内分泌信号比较慢
and by the time the hormone gets to its receptor,
当内分泌激素到达它的受体时
it’s a weaker message compared to paracrine or autocrine signaling
与配体浓度更高的旁分泌和和自分泌信号相比
where the ligands are more concentrated.
它的信号比较弱
So they’re slower,
虽然比较慢
but their message lasts longer and reaches more cells.
但它们作用时间长且影响范围广泛
And that’s exactly why we’d want to use them.
这正是我们要用内分泌信号的原因
Take growth hormone, a hormone secreted by the pituitary gland
例如生长激素 一种由垂体分泌
that promotes the growth of tissues like bone and cartilage.
能够促进骨骼和软骨等组织生长的激素
Clearly, we don’t just have a single patch of bone tissue hanging out next to the pituitary gland,
显然 我们并不是只有一块位于垂体旁边的骨头
so paracrine signaling won’t work.
因此旁分泌信号发挥不了作用
By secreting growth hormone into the blood,
而通过向血液中分泌生长激素
you make sure that
就可以确保
lots of different tissue gets this chemical message.
体内许多不同的组织会收到这种化学信号
Now, oftentimes endocrine signaling gets compared to a long distance call.
现在我们常将内分泌信号与远距离通话类比
And while it’s true that hormones can travel a long distance
虽然激素的确可以通过血液
through the bloodstream to their target,
被运送到距它们很远的靶点细胞
and that analogy isn’t perfect.
但这个比喻并不精确
It’s more like putting a bunch of messages in bottles,
它更像是将大量信息装进漂流瓶
and letting a river take them to your friends downstream.
通过河流将它们带给下游的朋友们
As you can see from the few examples in this video,
就像你在本视频中的例子看到的那样
a ton of functions around the body depend on
人体内很多功能都取决于
cell communication to happen in a timely manner.
及时的细胞通讯
One of them that we barely touched on in this video was the immune response,
本视频中我们几乎没有提到免疫反应
a topic that requires some more attention.
因为免疫这一话题需要更多的关注
In the next episode,
下期视频
we’ll discover how our immune cells learn how to fight off invading pathogens
我们将学习免疫细胞如何学习对抗入侵的病原体
and how they never forget.
及如何永久免疫
Thanks for watching this episode of Seeker Human.
感谢收看人类探索新闻台
I’m Patrick Kelly.
我是 Patrick Kelly