Gravity and the human body - Jay Buckey
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0:07 - 0:09Some of the issues that are important
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0:09 - 0:10if you want to have people in space
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0:10 - 0:12for long periods of time.
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0:12 - 0:14One is that people will tend to lose
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0:14 - 0:16bone and muscle mass.
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0:16 - 0:17We know this.
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0:17 - 0:18If you have to put a cast on your leg,
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0:18 - 0:20and you take the cast off after a few weeks,
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0:20 - 0:24you'll see that your muscles have shrunk in size.
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0:24 - 0:26And if you measured the bone strength,
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0:26 - 0:29you'd also see that might have gone down a little bit, too.
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0:29 - 0:32And so, it's very interesting that our body has that ability
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0:32 - 0:34to adapt to the loads that are put on it,
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0:34 - 0:36so that bones and muscles aren't static,
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0:36 - 0:38they're always changing.
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0:38 - 0:40While we think of bone as being a solid thing
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0:40 - 0:42that doesn't change very much,
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0:42 - 0:43it changes too.
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0:43 - 0:46And it turns out that in weightlessness,
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0:46 - 0:47you lose bone.
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0:47 - 0:49And then you also cause the muscles
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0:49 - 0:51that work against gravity,
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0:51 - 0:53what are called the postural muscles,
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0:53 - 0:56they'll start to shrink and lose strength.
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0:56 - 0:58There are other things in the cardiovascular system,
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0:58 - 1:00the heart and blood vessels.
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1:00 - 1:01And if you think about it,
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1:01 - 1:04standing up in gravity
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1:04 - 1:06means you have to work against gravity
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1:06 - 1:08in order to keep blood pumping to your head.
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1:08 - 1:11So, if you couldn't keep blood pumping in the head,
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1:11 - 1:14you'd pass out every time you stood up
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1:14 - 1:15because when you're lying down,
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1:15 - 1:17you don't have to push against gravity.
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1:17 - 1:18But when you stand up,
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1:18 - 1:20you got to work against gravity
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1:20 - 1:21to keep blood flowing to your head.
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1:21 - 1:23And your heart and blood vessels
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1:23 - 1:25have a really nicely worked-out system
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1:25 - 1:27to make that happen every time.
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1:29 - 1:32But that system can also change in weightlessness.
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1:32 - 1:34And then the other area that changes
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1:34 - 1:36is the system that has to do with balance.
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1:36 - 1:38Again, maintaining your balance
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1:38 - 1:41is something that you're doing against gravity, right?
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1:41 - 1:43If you didn't have gravity present,
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1:43 - 1:46you wouldn't have to worry about falling.
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1:46 - 1:48But you obviously do have to worry about falling,
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1:48 - 1:51and we have a very highly developed sense of balance
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1:51 - 1:52to keep us upright
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1:52 - 1:54and to prevent us from falling.
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1:54 - 1:56And when you see what skaters do,
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1:56 - 1:59you realize just how exquisite a system it is.
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1:59 - 2:01But when you go into weightlessness,
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2:01 - 2:03your balance system changes.
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2:03 - 2:04You don't really notice it
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2:04 - 2:05while you are in weightlessness,
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2:05 - 2:07but when you come back,
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2:07 - 2:08you do notice it,
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2:08 - 2:09that your balance has changed
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2:09 - 2:10and you have a little bit of trouble
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2:10 - 2:12maintaining your balance.
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2:12 - 2:15And what it shows is that while you're in space,
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2:15 - 2:18your brain is trying to allow you
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2:18 - 2:20to function in weightlessness.
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2:20 - 2:22And so, it re-adapts you to be weightless,
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2:22 - 2:24which you don't notice until you come back
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2:24 - 2:27and find out that you're now back on Earth
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2:27 - 2:30with a balance system that's been adapted to space.
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2:30 - 2:33You know, all life developed here on Earth
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2:33 - 2:35with gravity being present,
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2:35 - 2:39so life evolved under the influence of gravity,
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2:39 - 2:42and then we grow up with gravity being present,
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2:42 - 2:44so we learn how to walk
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2:44 - 2:45and catch a ball
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2:45 - 2:46and ice skate
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2:46 - 2:47or whatever,
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2:47 - 2:50all with gravity being present.
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2:50 - 2:54And what if you were to grow up without gravity?
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2:54 - 2:57What about the systems that depend on gravity,
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2:57 - 2:59like your muscles
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2:59 - 3:01or your balance system
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3:01 - 3:04or the heart and blood vessels?
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3:04 - 3:05Would they develop normally,
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3:05 - 3:08or would they be different in some way?
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3:08 - 3:09One reason why you might think
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3:09 - 3:12that it would go down a different pathway
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3:12 - 3:13is from an experiment
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3:13 - 3:15that was done some time ago
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3:15 - 3:17by two neuroscientists
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3:17 - 3:18called Hubel and Wiesel.
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3:18 - 3:22And what they did is they had a kitten,
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3:22 - 3:25and they put a patch over the eye of the kitten.
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3:25 - 3:27And then the kitten grew up to be a cat,
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3:27 - 3:30and they removed the patch.
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3:30 - 3:32And so, the question is,
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3:32 - 3:35can the cat see out of that eye?
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3:35 - 3:37Now, there's nothing wrong with the eye, right?
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3:37 - 3:39But it just hasn't seen anything,
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3:39 - 3:42there hasn't been any light coming in.
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3:42 - 3:46And the answer is that the cat can't see out of that eye
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3:46 - 3:49because what happens is that the brain
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3:49 - 3:51goes down a different pathway when it develops
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3:51 - 3:54and the connections that would ordinarily develop
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3:54 - 3:56to that eye don't develop.
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3:56 - 3:59And that can't be undone,
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3:59 - 4:00that's a permanent change.
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4:00 - 4:02So, the brain of that cat
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4:02 - 4:05is fundamentally different from the brain of a cat
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4:05 - 4:08that grew up seeing out of that eye.
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4:08 - 4:11That cat grew up with a different brain, in essence.
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4:11 - 4:12So, then you wonder,
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4:12 - 4:14well, what about gravity?
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4:14 - 4:15What if you don't have the forces
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4:15 - 4:17that gravity produces?
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4:17 - 4:20Is your balance organ going to develop
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4:20 - 4:21in the same way,
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4:21 - 4:23or will it be different?
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4:23 - 4:25If somebody grew up in space,
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4:25 - 4:27could they come back to Earth and function,
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4:27 - 4:31or would they really be a different person?
- Title:
- Gravity and the human body - Jay Buckey
- Description:
-
View full lesson: http://ed.ted.com/lessons/gravity-and-the-human-body-jay-buckey
Our bodies function necessarily under the presence of gravity; how blood pumps, a sense of balance and bone growth are all due to life in a world where gravity is an inescapable reality. Armed with experiments from neuroscientists David Hubel and Torsten Wiesel, astronaut Jay Buckey presents a thought experiment: How would our bodies work without the force of gravity?
Lesson by Jay Buckey, animation by TED-Ed.
- Video Language:
- English
- Team:
- closed TED
- Project:
- TED-Ed
- Duration:
- 04:46
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Andrea McDonough edited English subtitles for Gravity and the human body - Jay Buckey |