Human Senses - S1.E6 ∙ Balance
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TVTranscript
00:00It keeps us standing, it helps us move and it tells us which way is up.
00:07It's our sense of balance and I'm going to give mine a workout that's out of this world.
00:12This plane is used by the Russians to train their cosmonauts.
00:13In a short while it's going to drop like a stone and I'm going to experience weightlessness.
00:14This plane is used by the Russians to train their cosmonauts.
00:21In a short while, it's going to drop like a stone, and I'm going to experience weightlessness.
00:32I'm on board what's called the Vomit Common, and after a steep climb, we're going into freefall.
00:39My first one, I'm so nervous!
00:42How on earth am I going to cope with an environment that my sense of balance was never designed for?
00:49Woah!
01:07Tonight, we're going to discover the secrets of our sense of balance.
01:11How we can do this, and even this.
01:14But then this makes us fall over.
01:19You feel really sick. Everything's just turning and turning about until you just fall to the ground.
01:26I'm Nigel Marvin, and I'm going to reveal why everything we do is an incredible challenge for our sense of balance.
01:35I'll discover how we keep track of exactly how our bodies are moving, even when the world is spinning around us.
01:44And what it takes to bring it all crashing down.
01:50I've spent my whole life studying animals, but there are very few that can tell me about our strange human sense of balance.
02:00We're one of a very select club of creatures that get about on just their hind legs.
02:08There are only two kinds of animals that spend much of their lives performing that tricky balancing act of walking on two feet.
02:17Us, and a few flightless birds.
02:22And neither of us has the ideal design for it.
02:29If you wanted to design an animal to balance on two legs, you wouldn't necessarily end up with a human being or an ostrich.
02:40An ostrich has to work really hard not to topple over.
02:43A lot of its body weight is hanging over the front of its legs.
02:49Our body mass, on the other hand, is easier to handle, with a nice upright torso with all our weight directly over our legs.
02:59But our problem is a big heavy head at the top that can tip us over.
03:03And if walking on two legs isn't hard enough, we go and make things even more difficult.
03:09What makes life really tough for our human sense of balance is the crazy things we do with our bodies.
03:23Unlike any other animal, we take pleasure in devising new ways of balancing.
03:28And because we do all this, it's a monumental challenge to keep track of where we are at all times.
03:40The world can be a pretty confusing place.
03:44Which way are we moving?
03:47And which way are we going?
03:50The world can be a pretty confusing place.
03:55Which way are we moving? Which way are we spinning? Which way is the right way up?
04:01What exactly is going on?
04:06In order to keep control, you have to know how your body is moving through space.
04:11And when you're a stuntman like Mark Pass, being aware of your own movements is vital to the job.
04:19I mean, your coordination, your balance systems, you've got to use them with pinpoint accuracy, haven't you?
04:25As we're doing now.
04:27Yeah, absolutely. I mean, it's really important for every stuntman to have good body coordination, know where they are in space.
04:34Otherwise, it could be a matter of life or death.
04:36As if you're spinning in a car or dropping from a helicopter.
04:39Absolutely.
04:41So how do we sense which way our body is moving?
04:45For that basic information, we rely on a set of special balance organs deep within the ear.
04:52This series of tubes and chambers, no bigger than a pea, monitors every move made by our head.
05:00So, when we take off.
05:06Or skip to a halt.
05:09Or go into a spin.
05:15These movements are sensed within the inner ear.
05:19The tubes are full of fluid.
05:22Inside the tubes, there are tufts of microscopic hair cells.
05:26When we move our heads, the fluid moves and the hair cells are bent.
05:31They send nerve signals to the brain.
05:34The tubes point in three different directions and that's how we can sense movement in three dimensions.
05:39Some moves, well, they get the whole system going.
05:43Is this it, Mark? Here you go.
05:47The balance sensors in the ear tell us one other vital thing.
05:51Which way is up?
06:10And which way is down?
06:18Flipping hell.
06:20Thanks, Mark. Well done.
06:22You don't have to throw your body around that violently to test your balancing systems.
06:27Sometimes, even standing upright can be a challenge.
06:31Getting around on two legs means we need to know what virtually every inch of the body is doing.
06:37So, walking is an incredible challenge.
06:45Most of the time, we're actually balancing on one foot.
06:49As we move, almost every muscle in our body is involved in a furious battle to stop us from toppling over.
06:56So, besides the balance organs in the ear, we need sensors in our limbs and torso to let the brain know what the body is doing.
07:06Within a fraction of a second, the brain sends out millions of signals to the muscles to make corrections that keep us balanced.
07:15But we're actually born without any ability to balance upright at all.
07:21We have to learn it through trial and error.
07:28And it takes years before the information between our limbs and our brain can be used to help us balance upright.
07:34Eventually, walking becomes second nature.
07:37But it's such a complex operation that even the tiniest change can upset everything.
07:43Like puberty.
07:48And it's not just walking.
07:50It's the way we move.
07:52It's the way we move.
07:54It's the way we move.
07:56It's the way we move.
07:58It's the way we move.
08:00It's the way we move.
08:01It's the way we move.
08:06With our bodies growing so fast, the nerve circuitry in our brains can't keep up with the changes to the body.
08:14The wrong signals are sent to the limbs and so for a while we're gawky and clumsy.
08:20When you realise just how difficult walking is,
08:24it's no surprise that anything a little bit more tricky takes a phenomenal amount of practice.
08:39It's not just our bodies we have to balance on our two legs.
08:43We also pick things up and put them together.
08:45It's not just our bodies we have to balance on our two legs.
08:48We also pick things up and carry them around.
08:52Doing this creates an even greater challenge for our sense of balance.
09:00The secret of our success is that we actually prepare ourselves before we do it.
09:07Take a look at this.
09:09We've set up a simple test with a suitcase, some weights and a group of unsuspecting volunteers.
09:16First, the suitcase is filled with around 12 kilos of weight.
09:24The volunteers are asked to pick up the suitcase and repeat the movement a few times.
09:31Then we take them out of the studio and ask them a question that has nothing to do with the experiment.
09:36So it's actually an observational test. Did you notice the colour of the cameraman's t-shirt?
09:42Erm, no.
09:44And while the volunteer is preoccupied, we replace the weighted suitcase with an empty one.
09:50OK, we'll go back to our studio.
09:51OK, we'll go back to our studio.
10:01Because they don't know that a switch has been made, they automatically balance themselves for a heavy case.
10:17So they falter, but they don't fall over.
10:22Amazingly, it takes just a fraction of a second for our sense of balance to detect what's wrong, adjust and keep us upright.
10:36With our top-heavy design, moving around on two legs is a fantastic balancing act.
10:43We use sensors in the ear and throughout the body to guide constant, minute adjustments to thousands of muscles.
10:51But there's one other vital component to our sense of balance.
10:59To see that vital component in action, I've come here to the Circus Centre in San Francisco.
11:10It's awe-inspiring what these acrobats can do, and some of these manoeuvres, they take years of training.
11:16But I've come to see a stunt that will test even their sense of balance to the absolute limit.
11:24We've asked these acrobats to perform one of the most difficult stunts in their repertoire, the Human Tower.
11:30It's going to take four people, nerves of steel and a very strong foundation.
11:37And you're the base man, you know, that's a pretty tough job. What do you have to do?
11:42Well, basically I have to be the floor, or at least do my best to be the floor.
11:46So I have to be as solid and as strong as possible and provide the people on top of me the best foundation that I can.
11:53So let's see this in practice then. Let's see what you and your friends can do.
11:59It's teamwork. Everybody should be working together. Back strong, legs strong. Stay there. Stay tight.
12:08Okay? Thank you. Good luck.
12:11Alright, let's do it.
12:13Are we ready?
12:14I'm just going to hang on.
12:20As each person is added to the tower, the problems multiply.
12:24If the tower is to stay standing, everyone has to stay as perfectly still and upright as possible.
12:31Tighter. Shoulders and the back. Legs. Special legs.
12:36It's a hair-raising test for their sense of balance.
12:39Look up a little bit. Yes. Hold it.
12:41Every detail supplied to the brain by the sensors in the inner ear and the limbs is crucial.
12:47Stomach.
12:49But it's actually something else that's keeping Alec's team standing.
12:55Lift.
12:57Neither the movement sensors in their heads or their limbs can stop the really minute wobbles.
13:02For that, they need their eyes.
13:05Their eyes tell them when they're swaying even slightly, because they can see the room's moving.
13:12So how well will they manage without their eyes?
13:16To find out, they've agreed to build the tower again, but once they're up, we're going to turn out the lights.
13:25They won't be able to see anything, but we'll be able to with the help of this thermal imaging camera.
13:31Okay, Alec, this is the moment of truth.
13:35Are you steady?
13:37The troop is going to attempt a tower of three.
13:41Yes.
13:43Okay, are you steady now?
13:48There we are. A tower of three.
13:51Okay. Totally controlled, totally poised.
13:54Okay. Three, two, one, go!
14:02Can these masters of balance keep the tower standing in complete darkness?
14:07I hear the feet shuffling already.
14:12You've gone. That didn't take very long.
14:17Bad luck, but I reckon this is still a world record.
14:21As far as we know, no one has ever maintained a tower of three in the dark,
14:25because it's so difficult to balance without the help of your eyes.
14:31As far as I'm concerned, that really is pretty good proof that the balance sensors in our ears and in our limbs,
14:36they collect the basic information, but when it comes to really precise manoeuvres,
14:42they need a little help from our eyes.
14:46In fact, we all rely on vision when it comes to keeping our balance.
14:51Standing on one leg is a bit tricky, but with eyes open, most of us can do it for quite a while.
14:57But what happens when you close your eyes?
15:07You quickly discover how much vision is keeping you upright.
15:26Yeah, I lose balance a bit when I close my eyes.
15:29What was that?
15:37Our sense of balance is an extraordinary combination of three separate sensory systems in our ears, our limbs and our eyes.
15:53When they're all working together in harmony, we can even stay upright in the most testing situations.
16:07But all of the time, our balance system operates right at the limit,
16:12so even the slightest malfunction can send us crashing to the floor.
16:23When we move around, the inner ear is normally superb at sensing the movement,
16:28but it's actually quite a delicate system.
16:36These junior school children from West London have volunteered to be thrown off balance.
16:43Games which involve running about and making quick turns are no problem,
16:48but change the movement slightly and it's a very different story.
16:57If you keep spinning round and round, the fluid in your balance organ starts to move round and round too.
17:04The problem starts when we stop.
17:25Well, at first you feel like you're moving around with the earth,
17:28but when you stop, the earth seems to move round without you.
17:35We may have stopped spinning, but the fluid in the ear is still moving,
17:40so the brain thinks we're still turning round and round.
17:44We feel really sick. Everything's just turning and turning about until we just fall to the ground.
17:51But it's not just children's games that throw us off balance.
17:55The over-18s have a ways too.
18:03When we stop, the fluid in the ear is still moving,
18:07but when we stop, the fluid in the ear is still moving.
18:13The world moves in a mysterious way
18:16if the signals from the balance centres in our brain are disrupted or delayed in any way.
18:22And there's a liquid that's very good at doing just that.
18:26Alcohol.
18:29If we drink enough alcohol, it starts to disrupt the nerve signals in the cerebellum.
18:34That's the brain's balance centre.
18:37It's the part of the brain that coordinates all our movements
18:40and our muscles, particularly in the legs.
18:43And once you start affecting the cerebellum, the tendency is to sway all over the place.
19:01Alcohol slows down the nerve signals from the brain to the legs,
19:05which destroys our sense of balance.
19:07So before the advent of the breathalyser, the test for drunk drivers was walking the line.
19:17But alcohol can have a second effect on our sense of balance.
19:21Drink enough of it, and it even starts to mess with the balance organs in our inner ear,
19:26which creates a very unpleasant sensation.
19:30It's called the screaming horizontals.
19:33It's when you put your head back, particularly if you have your eyes closed as well,
19:37that suddenly the room seems to take off.
19:40The world starts to lurch, and it makes you feel quite sick and disoriented.
19:47The alcohol in the blood gets into the inner ear, affecting the tiny hair cells which sense movement.
19:53That tricks the brain into thinking that movements are much more exaggerated than they are.
20:01So a small move feels like a complete 360 degree head spin.
20:07It's a foolish party, it's all that I'm giving up to.
20:12Well, OK, I'm a little bit dizzy to be perfectly honest.
20:16But apart from that, not too bad.
20:24We rely on our separate balance systems to work together to keep us upright.
20:29But what happens if they're each telling us different things?
20:38Southeast 5, increasing 6 to gale 8.
20:42Veering south later, perhaps severe gale 9 later in Portland.
20:46Rain, good and poor.
20:49Southeast 5, increasing 6 to gale 8.
20:52Veering southerly gale 8, or severe gale.
20:57Out here in the North Sea, it's hard work putting one foot in front of the other,
21:02let alone keeping down lunch.
21:05These conditions, they really aren't great for a pleasure cruise.
21:10But they are perfect if you want to learn about seasickness.
21:15Even though I'm being chucked around, the sensors that make up my sense of balance are all working perfectly well.
21:22So why do I feel queasy? And why, if I go below deck, is it even worse?
21:28It's only wobbling around a bit. How are you feeling?
21:32Who better to explain why than former Rear Admiral Frank Golden.
21:37Frank, so why is it people feel more seasick below deck?
21:41The fluid in the inner ear is sloshing around, telling the brain that there's violent movement taking place.
21:47But sadly, that's not being confirmed by the eyes.
21:50The eyes really are perceiving everything as fairly static.
21:52I'm looking at a man who's barely moving, but my inner ear can sense that the boat is crashing up and down.
21:58The different components of my sense of balance just can't agree, making me feel awful.
22:04Is it the same principle when people try to read in a moving car and get car sick?
22:09Absolutely identical situation. Another conflict of sensory information going to the brain.
22:14Yeah, I'm sorry, I'm feeling a little bit nauseous. Can we go up on deck?
22:19With pleasure.
22:20Up on deck.
22:23Back on deck, I can see the horizon bouncing around, which confirms just how much we're moving about.
22:31Now all the parts of my balance system are telling me the same thing, and I feel much better.
22:38Believe it or not, there's another situation that tests our sense of balance even more than these rough seas.
22:46We make life hard by throwing ourselves around like no other animal on the planet.
22:53Even our ability to walk upright is a massive achievement for our sense of balance.
22:59But we don't stop there. We're always testing how far we can go.
23:05And we push ourselves even further by going where no creature on Earth was ever meant to go,
23:12by venturing into the weightlessness of space.
23:19But if our sense of balance is so precarious, how on Earth will I deal with weightlessness?
23:25To find out, I've come to Star City in Russia.
23:28This is a Russian jet plane that's been modified for a very special purpose.
23:33When this thing gets into the air, it does something that's extraordinary.
23:41For decades, the Russians have been using zero-gravity flights to prepare cosmonauts for life in space.
23:48Hope I'm all right.
23:51The conditions are so severe, unless your body's up to scratch, you aren't safe.
23:56If your body's up to scratch, you aren't allowed to fly.
24:01How am I?
24:03Like a cosmonaut.
24:05Like a cosmonaut. Thank you.
24:10Now I've passed the medical, there's no turning back.
24:14Every little kid wants to experience what it's like to be an astronaut floating in space.
24:19This is going to be a very special flight. I'm nervous about it.
24:22Some people in this plane, they get so sick, they've got to go to hospital and be on a drip,
24:28because they lose so much fluid when they're being sick.
24:36To create zero-gravity, the pilot has to execute an enormous arc at 25,000 feet.
24:46First, the plane makes a steep climb at full throttle.
24:50Then the power's cut, and the plane arcs over into a dive.
24:56And everything on board becomes weightless.
25:01The steep climbs and nosedives are so ferocious, that according to some cosmonauts,
25:07a trip on the Vomit Comet is tougher on our sense of balance than space itself.
25:13This is going to be like learning to walk again.
25:15My first one, I'm so nervous.
25:24Look at this. I can't feel my arms.
25:28I'm feeling soaked. It's like I don't know where my hands and arms are.
25:34And I'm feeling, oh, squeezy too.
25:38Will my balance systems ever get used to this?
25:42Will they ever get used to this? Oh, my goodness.
25:50To find out if they will, I'll be lifting off several more times.