Gravity and the human body - Jay Buckey

重力与人体--杰 巴克利

翻译人员: stas zhu 校对人员: Zhiting Chen

Some of the issues that are important

如果人类想长期置身太空

if you want to have people in space

有几个重要的问题

for long periods of time.

（不得不考虑）

One is that people will tend to lose

其中之一就是

bone and muscle mass.

骨质疏松与肌肉萎缩

We know this.

我们都知道

If you have to put a cast on your leg,

如果在你的腿上打上石膏

and you take the cast off after a few weeks,

几周之后取下石膏

you'll see that your muscles have shrunk in size.

你会看到你的肌肉体积萎缩了

And if you measured the bone strength,

并且如果你测量骨骼的强度

you'd also see that might have gone down a little bit, too.

也将看到些许下降

And so, it's very interesting that our body has that ability

而且，我们的身体可以适应加在之其上的负重

to adapt to the loads that are put on it,

这是相当有意思的。

so that bones and muscles aren't static,

所以我们的骨骼和肌肉不是永恒不变的

they're always changing.

它们在不停发生变化

While we think of bone as being a solid thing

即使我们认为很牢靠的骨骼

that doesn't change very much,

并不怎么变化

it changes too.

但其实它也会变化。

And it turns out that in weightlessness,

事实上，在失重状态下

you lose bone.

骨质会发生流失

And then you also cause the muscles

并且

that work against gravity,

我们称之为“肌姿势”的

what are called the postural muscles,

用以对抗重力的肌肉

they'll start to shrink and lose strength.

也会开始萎缩并失去力量

There are other things in the cardiovascular system,

再来看看心血管系统：

the heart and blood vessels.

心脏及血管

And if you think about it,

你想象一下

standing up in gravity

你在重力环境下站起来

means you have to work against gravity

必须对抗重力

in order to keep blood pumping to your head.

以保证血液流向头脑

So, if you couldn't keep blood pumping in the head,

所以，当你不能保证血液流向头脑

you'd pass out every time you stood up

你每次躺下后起身会会感到头晕

because when you're lying down,

这是因为当你躺下来的时候

you don't have to push against gravity.

不需要对抗重力

But when you stand up,

但是当你站起来的时候

you got to work against gravity

你必须再次对抗重力

to keep blood flowing to your head.

以保障血液流向你的头脑

And your heart and blood vessels

每当上述情况发生

have a really nicely worked-out system

你的心脏和血管

to make that happen every time.

有一套自发的应付机制。

But that system can also change in weightlessness.

但是在失重条件下这套机制也会变化

And then the other area that changes

另一个也会发生变化的地方

is the system that has to do with balance.

就是平衡系统

Again, maintaining your balance

同样的，保持平衡

is something that you're doing against gravity, right?

是在重力环境下做的事情，对吧？

If you didn't have gravity present,

如果没有重力存在

you wouldn't have to worry about falling.

我们也不用担心跌倒了

But you obviously do have to worry about falling,

但是很明显你需要担心跌倒

and we have a very highly developed sense of balance

并且我们已经有相当发达的平衡感知

to keep us upright

来使得我们保持直立

and to prevent us from falling.

并防止跌倒

And when you see what skaters do,

而且等你看过别人玩滑板之后

you realize just how exquisite a system it is.

你就会意识到这个系统有多么精妙了

But when you go into weightlessness,

但是当进入失重环境时

your balance system changes.

你的平衡系统跟着变化

You don't really notice it

在失重状态下

while you are in weightlessness,

你可能无法意识到这一点

but when you come back,

但当你回到正常状态

you do notice it,

你就会注意到

that your balance has changed

and you have a little bit of trouble

你的平衡能力已经发生改变

这时候想保持平衡

maintaining your balance.

会有点困难了

And what it shows is that while you're in space,

当你置身太空

your brain is trying to allow you

大脑会设法让你

to function in weightlessness.

失重环境下活动

And so, it re-adapts you to be weightless,

这样，你再次适应了失重环境

which you don't notice until you come back

在你回到正常状态之前不会意识到这些的

and find out that you're now back on Earth

落地之后你会发现

with a balance system that's been adapted to space.

你的平衡系统已经适应了太空环境

You know, all life developed here on Earth

你知道，地球上的生物

with gravity being present,

在重力环境下生存

so life evolved under the influence of gravity,

在重力影响下进化

and then we grow up with gravity being present,

在重力的前提下成长

so we learn how to walk

所以我们学会如何走路

and catch a ball

如何接球

and ice skate

以及溜冰

or whatever,

等等等等

all with gravity being present.

都与重力的存在息息相关

And what if you were to grow up without gravity?

那么如果你不是在重力环境下长大的呢？

What about the systems that depend on gravity,

那些依赖重力的身体系统怎么样呢

like your muscles

比如你的肌肉

or your balance system

或者你的平衡系统

or the heart and blood vessels?

或者心血管系统

Would they develop normally,

它们会正常发展吗？

or would they be different in some way?

或者会有所不同吗？

One reason why you might think

你可能觉得

that it would go down a different pathway

事情会朝另一个方向发展

is from an experiment

不久以前

that was done some time ago

两个叫做休博尔和维瑟尔的神经学家

by two neuroscientists

所做的实验

called Hubel and Wiesel.

替你给出了理由

And what they did is they had a kitten,

他们有一只小猫

and they put a patch over the eye of the kitten.

他们给小猫的一只眼睛戴上眼罩

And then the kitten grew up to be a cat,

小猫长大后

and they removed the patch.

他们为其取下眼罩

And so, the question is,

那么，问题是

can the cat see out of that eye?

它能用那只眼睛看到东西么？

Now, there's nothing wrong with the eye, right?

现在，眼睛本身没有任何问题，对吧？

But it just hasn't seen anything,

但是猫看不到任何东西

there hasn't been any light coming in.

这只眼睛感知不见任何光线

And the answer is that the cat can't see out of that eye

答案是，猫不能从那只眼睛看到任何东西

because what happens is that the brain

因为它在大脑发育的上

goes down a different pathway when it develops

出了岔子

and the connections that would ordinarily develop

本应该发育的与那只眼睛的连接

to that eye don't develop.

没有发育

And that can't be undone,

而且这是不可逆的

that's a permanent change.

这是一个永久的改变

So, the brain of that cat

所以，这只猫的大脑

is fundamentally different from the brain of a cat

与通过那只眼睛视物长大的猫的大脑

that grew up seeing out of that eye.

根本上是不一样的

That cat grew up with a different brain, in essence.

本质上，那只猫长出了一个不一样的大脑

So, then you wonder,

然后，你会奇怪

well, what about gravity?

好吧，那么重力怎么说？

What if you don't have the forces

如果失去重力的影响

that gravity produces?

会怎么样？

Is your balance organ going to develop

你的平衡系统将会以同样的方式

in the same way,

来发育吗？

or will it be different?

抑或是按另一种方式发育？

If somebody grew up in space,

如果有人在太空中长大

could they come back to Earth and function,

他们能回到地球上并且功能健全吗？

or would they really be a different person?

又或者他们实际上会变成一个不一样的人？