All language subtitles for National.Geographic.Incredible.Human.Machine.XviD.AC3.MVGroup.org.eng

There is nothing more familiar
or more mysterious...

more breathtaking in its action...

marvellous in its mechanics...

exquisite in its range of senses...

and staggering in its ability to understand.

On a fantastic voyage
through a single day,

we plunge deep into the routine miracles
of the human body.

Dream on, dream on...

Our instruments,

engines,

infrastructure,

roadways and circuitry.

Through 1 0,000 blinks,

20,000 breaths,

1 00,000 beats...

Hello.

..today is an ordinary, extraordinary day

in the life of the incredible human machine.

Bits of stardust is really all we are.

Oxygen, carbon, hydrogen

and a handful of elements that would cost
very little at any chemical supply shop.

But get these chemicals together,

marinate in a hospitable place
for about 3.8 billion years

and the mundane mix of molecules
becomes precious.

There are more than six billion human bodies
living on Earth

and each of us is the amalgamation of
some 1 00 trillion microscopic cells.

While the blueprint for each individual
are 99.9 per cent identical,

no two of us are exactly the same.

As a new day dawns,

each human machine begins
the succession of miracles

that will take it from morning to midnight.

Cells, senses,

muscles, bones,

hearts, brains,

all must marshal their forces and unite
just to wake us up.

(Alarm beeps)

(Sighs)

At the surface of it all,

a velvety overcoat of cells and protein
keeps us in

and the rest of the world out.

lt's our armour,

our radiator,

our entree to pain and pleasure.

lt is the body's largest organ -

our skin.

Smooth and silky to the eyes and touch

a closer look
presents a very different landscape.

Magnified 600 times,
our outermost skin is nothing but dead cells,

riddled with ridges and grooves

and pocked with countless bumps
and holes.

Look closer still and we find
hundreds of thousands of bacteria

inhabit every square inch of us.

With every tick of the clock,
our dead skin gets sloughed off.

We shed at least 600,000 particles of skin
an hour-

about a pound-and-a-half's-worth each year,

which accounts for as much as 80 per cent
of the dust in our houses.

But there's plenty of skin to go around.

lf we could peel it off and lay it out flat,

the average person's skin
would cover some 1 8 square feet.

Though just millimetres thick,

it would weigh about 6lb.

And we're constantly making more.

Just wait a month or so
and you'll have a shiny new coat.

Which means skin can't be all dead.

Dip below the surface
and you find cells continuously dividing

to replace those dead cells above.

Kilometres of blood vessels
pulse to skin's connective tissues.

Not forgetting
all those precious nerve endings.

45 miles-worth of nerves stretch
from our heads down to our toes,

and many reach to our skin.

Some parts more than others.

lf sensitivity were size-dependent,
we would look something like this.

Our supersensitive hands, feet,
tongue and lips,

each packed with touch receptors,
would swell enormously.

Our legs, on the other hand,
would resemble a chicken's.

Good thing for us there is more to this organ
than touch.

Skin is also our heating and cooling system.

And by helping maintain
that comfy 98.6 degrees Fahrenheit

it keeps us alive.

Through its network of blood vessels,

skin carries as much as one-third
of the heart's hot, freshly-pumped blood.

Get too hot and these vessels can widen
to release heat from our bodies.

But sometimes that's not enough.

A good workout can raise the body's
temperature several degrees above normal -

a potentially deadly state
if it weren't for skin's slick safety net..

sweat.

More than two million holes across our skin

can produce up to half a gallon of the liquid
in an hour.

The heated droplets evaporate into the air,
and leave the body cool.

Through a special camera that images heat,
not light,

we can see this air-conditioning system at work.

The hotter the body, the deeper the red.

No surprise, some of the warmest parts
of our bodies -

our foreheads, palms, and armpits -

correlate with the greatest concentration
of sweat glands.

But we're more likely to encounter the opposite
extreme in our morning routine.

Exposed to a chill,
tiny musclesjerk our hairs to attention,

bulging the skin around them.

We call them goose bumps.

Scientists have dubbed us ''the naked ape''.

But look closely

and we find we're anything but naked.

Some of our skin cells form tubes
that produce hair.

And we have as many of these follicles
punctuating our skin

as do our hairy relatives.

Some five million of them.

As the new hair cells divide,

they push old ones up and out.

By the time our hair breaches the surface,
it's dead.

Which is why we don't feel pain
with every haircut.

Cleaned and groomed,
we venture into the bustling morning world.

Around us, other incredible human machines
greet the day,

in all different sizes and shapes,

colours and textures.

But on some level, we all inhabit the same skin.

Below the surface, each of us has
about the same number of melanocytes,

the cells that pump the dark pigment melanin
into our hair and skin

and give them colour.

lt'sjust the amount of melanin
these cells produce

that determines whether we are black or white,
brunette or blonde.

Generally speaking,
the more melanin, the darker.

That same chemical adds colour
to a very different sensory organ.

Blue or brown,

green or hazel,

they are the most vital sensory organ
that the incredible machine has.

Our day hasjust begun,

and the magnificent miracle of sight
leads the way.

Navigating the morning rush hour is something
most human machines do on autopilot,

oblivious to the staggering task
we leave to two gelatinous orbs.

Eyes sit squarely on the front of our faces
for a reason.

Peering forward, and set apartjust enough
to let us gauge distance,

they let us spot and track whatever we desire.

ln microseconds, our eyes sight, follow,

focus and process images
fractions of an inch long

or moving at hundreds of miles per hour

enabling us to assess and appreciate
the world around us more than any other sense.

They may be the windows to our souls,

but on a less poetic level,
eyes are just hungry harvesters of light,

trapping and translating it into
electrical impulses the brain can understand.

Light hits the cornea first.

This transparent layer, cleansed and lubricated
about 1 0 times a minute with every blink,

admits and directs incoming light rays.

From there, they pass through
the dark opening of the pupil,

then a transparent protein lens.

Gatekeepers of light, the muscles of
the colourful iris squeeze the pupil closed

against too much light.

Not enough, the iris relaxes
and the pupil opens.

And in just a fraction of a second,
it can slide back and forth between the two.

Focused by cornea and lens,

light then flies through the jelly-like bulk
of the eye and onto its rear wall.

Just about a hundredth of an inch thick,
this is the retina,

where more than 1 20 million photoreceptors
convert light into electrical impulses,

before processing
and shipping them off to the brain.

ln a mind-boggling feat that soaks up
about a third of our brain power,

our brains continually compare new data with
information processed a split second before.

Combine that with
what they already expect to be there

and vision is born.

At least, that's how it's supposed to work.

When it doesn't,
the world can look more like this.

62-year-old Linda Morfoot has a genetic disease
called retinitis pigmentosa.

which has been gradually degrading her
eyes'photoreceptors for the past 40 years.

They haven't turned light into sight
for the last ten.

lt's frustrating to lose your sight

because you run into things,
you run into people.

And it can be depressing.

Just open up real wide.

Very good.

Now, thanks to Dr Mark Humayun
of the University of Southern California,

she may see again.

All along we've been told it's impossible,
it's science fiction, it can't happen.

Look up.

Humayun has implanted an ingenious
little device at the back of Linda's eye.

Just 1 6 electrodes
that should act as a simple retina,

turning light into impulses
that can be sent to the brain.

We lay it right on the retina

and the current stimulates
the underlying nerve cells.

When this information is received by the brain,
you see a spot of light.

To perceive those spots, Linda had to first wear
a special pair of sunglasses that capture light,

convert it into electrical signals,

and fire up the implants in her eyes.

As the doctors activated the electrodes
one by one,

it started to work.

lt was crude,
but Linda could now see light and movement.

As they turned more and more electrodes on,

l could see the lights on
or the doorway.

l could tell the difference
between black and white.

lt was exciting. Yes, it was.

1 6 signals hardly compares to the million or so
a working retina transmits.

But with each passing day,
her brain compensates,

and Linda sees more detail.

We thought that 1 6 electrodes would never ever
give Linda or any other patients

the level of vision they have been able to attain.

The brain fills in the missing gaps.

From simple flashes of light

our brains can somehow conjure
meaningful images.

So, now, after 1 0 years of blindness,

Linda can see the grandchildren
she never saw before.

They like to run in front of me.
''Where am l, Grandma? Where am l?''

l'm more connected to them,

a little more part of their lives, you know.

Even for those of us lucky enough
to see 20/20

the sense of sight does not work alone
in the incredible human machine.

On either side of our heads
are the body's microphones - ears.

But ears do much more than hear.

They give us balance, telling us
where we are in space at any given moment.

Riding a bike, landing,

perfecting a dive,

even taking a baby step,

all would be impossible without
the intricate gadgetry deep inside our ears.

Here, three fluid-filled tubes work like
carpenters'levels to help keep us balanced.

When we turn our heads, the fluids move,
stimulating nerve cells,

and orienting the brain in three dimensions.

Up-down, left-right,

forward-backward.

lt's a powerful little mechanism
that we can stimulate artificially.

Welcome to the weird world of tomorrow.

With a special electrified headset,

scientists in Japan have taken hold of
our balancing centres.

By sending current down to those nerves
in our inner ears

they've created remote-controlled
human beings.

TRANSLATOR: l've never experienced
such a sensation.

lt was like being drunk on the deck of a boat
rocking in the waves.

The current is low voltage,

just enough to throw people off balance
and compel them to walk left, right,

even trace the shape of a giant pretzel.

TRANSLATOR: My body was out of control.

lt was swaying to the left and to the right.

We can even remote control ourselves.

We're not trying to control people

or manipulate their actions.

Rather, we want to help them,

help guide them.

Especially people with balance problems
or dizziness.

The researchers say one day it may even help
navigational devices, like GPS,

to physically guide us to our destinations,

or make a video game
feel more like a rollercoaster.

Our ears provide another powerful sensation
to enrich our day.

Every time we, or anything else for that matter,

make a move or vibrate,
we create ripples in the air.

Distinct waves all travelling at
different frequencies,

which waft into our ears at some 750mph

and produce sound.

Like radar dishes, our ears channel
the sound waves deep into our skulls.

Our eardrums vibrate in tune to the frequencies,

moving three tiny bones,
each about as long as a grain of rice.

Magnified 20 times we can see the ear
hear,

inside...

..and out.

Love in an elevator

Livin' it up when l'm going down

Love in an elevator

Turnin' it up till l'm upside down...

The bones'movements get converted to pulses
of pressure

which vibrates fluid

which disturbs tiny hairs

which excite nerve cells

which translate all of this to the brain.

One sound perhaps more than any other
is music to our ears -

the human voice.

lt's an astonishingly versatile instrument,
but it's vulnerable.

As lead singer for Aerosmith,

Steven Tyler's work depends on his vocal cords.

l need a girl like an open book

To read between the lines

Few of us think about the trauma we generate
in our voice boxes when we talk, sing, laugh

or scream.

But if you were to look down the gullet
of Steven Tyler,

it would show why he,
and millions of others,

are wreaking havoc on a delicate instrument.

Thank you!

Tonight, as Aerosmith perform,

Dr Steven Zeitels and his team
from Massachusetts General Hospital

will get a rare treat.

With the help of special
monitoring equipment

they'll see how this famous pair of vocal cords
holds up to such extremes.

Dr Zeitels, one time for my kids,
what is this monitoring?

What we're going to be doing is looking at
the vibrations on the skin of your neck,

which is going to pick up the intensity
of your voice,

it's going to be picking up the loudness
of your voice.

Thank you, Doctor.

lnto the abyss.

lnto the great beyond with Dr Zeitels.

Backstage throughout tonight's concert,

Zeitels will use an endoscope
to examine Tyler's voice box up close.

Try not to touch the sides.

Stick your tongue out for me.

Just breathe. Say ''Ah''.

Ahhh!

lt's a rare insight into what goes on
in a high-performance singer.

Real time measures of a performer

who is at the top of his game

doing a live performance
in front of thousands of people -

that's a first, hasn't been done before.

(Sings high note)

(Laughs)

To produce these kinds of sounds,

Tyler's vocal cords are slamming together
an average of 1 70 times a second.

That's more than half a million times
during the course of a concert

and nearly a billion times during the course
of his 30-year professional career.

There's no part of the human body

that likely sees these kinds of collision forces
and shearing stresses,

which is why vocal folds
essentially wear out over time.

lt's also why just months earlier damaged
vocal cords cancelled much of Aerosmith's tour.

Tyler could barely sing...

(Sings high note)

Just breathe.

..forcing him to undergo Zeitels'knife,

or laser, in this case.

Steven basically had a vocal bleed,
which is very common in performers.

Common, in fact, to many with the gift of gab,

from attorneys to telemarketers.

The laser surgery,
which Zeitels and his team pioneered,

works by sealing off damaged vessels
to stop the bleeding.

This is Steven Tyler's voice box

and these are his fragile blood vessels
disappearing.

He was able to just zap those blood vessels

so l go out there and sing
and hope for the best.

Now, as Steven heads on stage,
his finely tuned vocal cords spring into action.

(Guitar intro)

This is Steven Tyler outside...

Every time that l look in the mirror

- ..and in.
- Every time that l look in the mirror

All these lines on my face getting clearer

Every time we exhale,

we force air through our
two membranous vocal cords.

When we bring them together, they vibrate.

Dream on...

These vibrations produce sound,

much like a guitar string after it's been plucked.

Dream on...

Muscles open and close the chords
and change the sound's pitch.

During low notes, the chords are loose
and vibrate more slowly.

Dream on, dream on, dream on...

But for those falsettos...

(High-pitched) Dream on, dream on

His chords stretch to the limit

and vibrate virtually off the charts.

(Holds high note)

A surprisingly simple feat
for Tyler's pliable chords.

l mean, to go from,

(Gruffly) ''l woke up this morning
on the wrong side of the bed

And how l got to thinking
And all them things l said''

but it's in that voice.

And then, you know, of course...
(Higher) ''And l don't want to miss a thing''

is in that voice.

And then Dream On is:
(Falsetto) ''Dream on, dream on''

and they've asked me before,
''How do you sing that song every night?''

That's one of the easiest ones
for me to sing.

Go.

(Rising pitch)

As for what translates these vocal vibrations
into song

that happens much further up

in the throat, the mouth,
the tongue, and the nose.

These are what put the stamp
on human sound,

distinguishing the likes of Steven Tyler
from just about anyone else.

After some two hours of vocal gymnastics,

initial data reveal that Tyler's chords
crashed together more than half a million times,

and covered the equivalent of
more than six miles.

To read between the lines

(Wild cheering)

And there's no indication
they'll be wearing out anytime soon.

Thank you!

Dramatic as it may be, singing is a side effect
of a much more crucial process.

The real reason why air passes through
our mouths is breathing.

We wouldn't survive much more than
a couple of minutes if we didn't.

With every inhalation our noses or mouths
suck in about a pint of air

some 20,000 times a day.

We can follow it on itsjourney down the throat

past the voice box

and into the windpipe or trachea.

As it approaches the lungs,

air has a choice - left or right,

but both lungs lead to the same end.

The lungs'bronchi divide and divide into
thousands of smaller and smaller branches,

progressively filtering chemicals,
dust and smoke in the air,

until finally they come to an end

in this pouch-like ball called an alveolus.

More than 300 million of them
spread across each lung

with a combined surface area
roughly a third the size of a tennis court.

ln less than a second,
oxygen molecules exit the lungs here

through wallsjust one cell thick.

They'll then cross into a surging bloodstream,

be whisked throughout the body

and provide precious resources
to every one of our trillions of cells,

assuming air gets to this point.

The blue here shows how a healthy lung
empties oxygen into the bloodstream.

ln this smoker's lung,
oxygen can't empty nearly as well.

Then there's the exhalation.

Carbon dioxide.

The waste product of breathing
makes the opposite journey back out.

Another inhalation and our breathing apparatus
offers yet another gift,

with delightful or disgusting results.

With every new breath, our noses can
distinguish as many as 1 0,000 different odours.

Some pleasing...

..some not.

They can calm, caution,
or make our mouths water.

But the essence of any aroma,
from a day at the beach to fresh baked bread,

is pure chemistry.

lsobutyl acetate, vanillic acid and more than
300 different chemicals, for example,

come together to give chocolate
its unmistakable bouquet.

A rose by any other name
might be phenyl ethyl alcohol.

And once fish is past its prime,

it owes its stench to trimethylamine,

a by-product of the bacteria growing inside it.

Whatever the chemical

deep inside our noses,
there is a small patch of about 1 0 million cells

waiting to sniff it out.

These cells carry about a thousand
different kinds of receptors on their surfaces.

When the right odour chemical
meets up with the right receptor

an electrical signal gets sent to the brain,

and, finally, the incredible machine smells.

All in all, our respiratory systems
are ingenious multi-taskers,

sorting thousands of smells at each intake,

capable of making thousands of sounds
on the way out.

(Laughter)

But no matter how pleasant the by-product,

there is a higher calling to breathing.

Every breath we take delivers oxygen
to our trillions of power-hungry cells

and gets our hearts to pump.

(Heartbeats)

Every second of every day,

every cell in our body needs oxygen
to power its activities and survive.

More than a gallon of blood needs to travel
through some 60,000 miles-worth of arteries,

veins and capillaries.

And one little 1 0-ounce heart has the
Herculean task of driving the whole system.

lt begins with a heartbeat

which sends fresh, oxygenated blood
from the lungs streaming into the heart.

lf you stored up the power
from all the heartbeats in a day,

it could lift a car some 30 feet into the air.

The heart is a muscular pump to its core.

Even if it's removed,
it can still function all on its own.

lts genius lies in its cardiac cells -

millions of them all beating in tune.

But heart cells don't necessarily
have to be born in the heart.

These are stem cells
coaxed into beating by Dr Amit Patel

and his colleagues from
the University of Pittsburgh Medical Center.

Those cells had nothing to do with
becoming heart muscle.

But within less than a week,

we were able to train them
to become heart muscle.

Stem cells live in many tissues in our bodies,

standing by for maintenance and repair.

Unlike our other cells, stem cells can develop
into just about any kind of cell -

brain, muscle, bone, fat.

Almost anything you could possibly think of
in the body,

over 220 different cell types,

all come from stem cells.

49-year-old Michael Carlat desperately hopes
that stem cells can turn into heart cells

in his own body.

A few years ago, his heart started to give out.

Catastrophically.

Mr Carlat's heart is very sick.

He had a very large heart attack.

When you look at the heart, it's a pump.

Normally, 60% of what goes into the heart
should come out with every heartbeat.

ln Mr Carlat, only 30% comes out.

l was put on this heart transplant list

and waited over a year for something to happen.

There's 4,500 people on the list.

l'm 275lb. l'm 6'4''.

lt's hard to find a match for me.

Waiting on that list would have been waiting to
play out the last couple of years and that'll be it.

With few other options,

Michael enrolled in
a highly-experimental clinical trial,

in which Patel performs a risky bypass
on his heart's damaged area,

extracts stem cells from his hip bone,

and injects them back into Michael's heart.

lt's not clear what these cells will do there.

Help grow new blood vessels?

lncrease the number of muscle fibres?

The hope is that they'll help coax Michael's heart
into healing itself.

We don't know what they do,
but they seem to know what's required.

And though it's early, in Michael's case
they already seem to be working.

Just three months after his surgery,

Michael's heart pumps 25% more blood
than it did before.

The difference between barely climbing
a flight of stairs

and playing basketball.

lt's working,
so l'm not going to ask why, how, what.

He saved my life.
lf l didn't go to him, l probably would have just...

..not been around today.

Of course, it takes more than just a good pump
to give life-giving liquids around the body.

lt takes good plumbing.

Once out of the heart,

blood carries our vital oxygen supply
through smaller and smaller arteries,

eventually reaching an even narrower
network of capillaries.

These tubes are so thin that red blood cells
thousandths of an inch across,

must squeeze through single file.

Ten billion capillaries fan throughout the body

so that our organs and tissues
are never far from a fresh supply of oxygen.

Carbon dioxide and other toxins need to get out

and veins are crucial drainpipes
carrying the blood back to the heart,

then to the lungs for cleaning.

Blood travels through
more than 60,000 miles of vessels -

more than twice around the Earth.

lt circulates all around the body
in less than a minute,

every minute of our lives.

And sometimes blood moves even faster.

The more oxygen our cells burn,

the harder our heart and blood vessels
have to work to deliver more.

When we eat, it rushes to our stomachs.

When we run, to our muscles.

Even when we read,
more oxygen must get to our brains.

As efficient as this blood delivery system is,
though,

it has its limits.

Limits experienced by pilots in the US Navy.

These are the Blue Angels,

the US Navy's elite flight exhibition team.

Experiencing up to 9Gs at times -
nine times the force of gravity -

these pilots routinely push their bodies
to extremes.

Well, 9Gs to me squashes me in the seat
pretty hard.

l weigh about 1 80lb, so it's nine times that.

l'm not going to do the math for you right now

but it squashes me pretty hard.

Some 1,600lb of pressure on solo pilot
Ted Steelman

is enough to push the precious
oxygen-carrying blood right out of his brain.

Same thing as if somebody strangles you
or anything like that.

You're going to lose blood to your brain
and you're going to pass out.

To counteract this
fighter pilots typically wear gravity or G suits,

which automatically inflate
to squeeze blood where it's needed.

Flying a mere foot-and-a-half apart,

the Blue Angels can't chance it.

The slightest jolt from a G suit on the stick
could be disastrous.

When you're talking about stick inputs
of as much as a sixteenth of an inch,

when you're doing 400mph
a mere 1 8 inches from the guy next to you,

it actually has huge ramifications.

So, no movement of the stick unless intended
is what you're looking for.

Which means that these pilots
must use their muscle

to force blood up to their brains.

What l do is what we call a hick manoeuvre.

lt's a culmination of breathing technique

in that you contract the chest with a ''hick-k''

to keep the overall pressure
within the chest cavity high

in about 3-4 second intervals

as well as isometric contractions
from the waist down.

By simply breathing and contracting muscles

the body can be trained to withstand
extreme forces.

To do it, pilots must face this - the centrifuge.

Like an extreme amusement park ride
that spins blood from brains to toes

and tests how long a pilot is able to resist.

They train their bodies,
like a marathoner will train their body

to go out and run 26 miles
at five-minute miles.

These guys train their bodies
to respond to the Gs.

Legs and glutes, keep them in.

But even highly-trained specialists like Steelman
can only defy physics for so long.

lt happened right at the very end of the run.

l expected a G release, so what did l do?
l relaxed my body.

The moment you relax,
the absolute moment you relax,

every single time you're going to pass out
under G like that.

Now, when Steelman takes to the skies,

he knows the warning signs
and takes evasive action.

Passengers, on the other hand,
are a different story.

You'll hear them executing the hick manoeuvre,
working hard,

and suddenly it gets quiet, and you look back
in the mirror and they just do this.

Their heads are down to their chest.

Fortunately, the effects are only temporary.

Whoa! Did we do it?

Blood is something our brains,
and the rest of our organs for that matter,

never want to be without.

But there's more to this liquid than oxygen.

ln a single drop of blood,

up to 400,000 infection-fighting white blood cells
are constantly patrolling

and seeking out foreign agents,
like viruses and bacteria,

and internal threats like cancer,

and attacking them.

Unfortunately, they don't always win.

And when that happens,

aggressors like these rogue melanoma cells
can grow out of control.

Whether our cells work with us or against us,

one thing is certain -

we are tirelessly working for them.

Since we woke up, our heart has beaten
more than 20,000 times,

bringing vital oxygen
to a hundred billion microscopic masters.

But it takes more than air to feed the machine.

lt takes fuel.

Every time we swallow a morsel of food,

we set it on a journey
designed to suck everything useful out of it.

Sit down to lunch, and in the 30 or so hours
and 20-plus feet it takes to digest it,

we convert plants or animals into energy

and absorb their chemical building blocks
into our own flesh and blood.

Carbohydrates, proteins, fats,
vitamins, and minerals -

all of our nutrients come from what we eat.

Digestion actually starts
before food crosses our lips.

Just the idea of food
can get our mouths to water.

We salivate roughly a pint every day.

And in that saliva are enzymes that,
along with our teeth,

begin to break down the food that we eat.

But not before we get to savour it first.

Some 1 0,000 taste buds line our tongues,

each one home to about 50 taste receptor cells
that tell the brain what we're eating.

And if some of those precious receptors
are scorched off,

it will only take a week to 1 0 days
to grow back a brand-new set.

Once the muscular tongue manoeuvres food
into our oesophagus, we're on autopilot.

When we eat, a flap of skin called the epiglottis
seals off our windpipes.

Except when it doesn't.

l'm OK.

Then it's back to the beginning.

A typical journey down the oesophagus
takes about five seconds.

From here it's squeezed, like toothpaste.

Once it passes into the stomach as it's doing
here it's time to slow down a bit and digest.

Normally this stretchy, J-shaped bag
isn't much bigger than a fist.

(Groan)

But after a big meal,
it can expand to more than 20 times that size.

For the next several hours highly acidic gastric
juices spew from the stomach's walls,

breaking down proteins in our food while muscle
contractions knead and churn it into a pulp.

The acid here is so strong the stomach must
continuously secrete a layer of protective mucus

so that it doesn't digest itself.

lt absorbs very few nutrients, though.

For that we pass into the 20-foot
''dis-assembly'' line of the small intestine

with the help of a specialised camera pill.

For about five hours, food's building blocks
are pushed, prodded,

sprayed with digestive juices
and wrung like a rag here,

until its vital elements
are forced through the intestinal wall

and into the bloodstream.

From here, most of our meal's nutrients
will flow directly to the liver,

the body's largest internal organ.

The liver breaks down, repackages and delivers
nutrients to our cells for growth and power.

Our bodies ultimately try to balance
energy intake.

But sometimes more goes in than out.

The result.. fat.

This is how fat looks on the inside...
and on the outside.

lt doesn't take a lot of excess calories
to make you gain weight.

Just 1 5 more a day than you need -
about the amount in four pistachio nuts -

will add a pound and a half of fat over a year.

Once the small intestine
has taken in everything worth ingesting,

the rest is pushed along to the large intestine.

For another 20 hours or so,
the last of the water is absorbed,

and billions of bacteria work to break down
the remaining contents.

ln the end,
anything we can't digest gets flushed...

(Toilet flushing)

..out of our bodies.

Food's complicated journey
has a larger purpose.

Once we've extracted what we need
to feed the incredible machine

and gotten our cellular engines humming,

it's nothing short of astounding
what we can do with them,

thanks to amazing contraptions called muscle.

The incredible human machine in action.

Just about every body part,
from our skin receptors

to the balance centre in our inner ears,

help to make these amazing complexities of
movement seem almost effortless,

automatic even.

But if we peer beneath our skin,

we see that one tissue above all
propels us into a thousand different positions.

From the soles of our feet
to the tips of our fingers some 650 muscles,

about 40% of our body mass,
power every move we make.

As our day pushes on,

these skeletal muscles lift us through it
usually without our thinking about it.

Without them we couldn't run or blink,
smile or speak for that matter.

Hello?

Just muttering a single word...

Hello?

(Prolonged) Hello?

..involves muscles in the face, lips, tongue, jaw,
larynx - as many as 1 00 muscles.

Many of the same muscles let us form a frown.

Turn them upside down and all 34 muscles
in the face let us deliver a kiss.

Walking,. a highly coordinated series of falls

that we've taken for granted
since we were toddlers

requires no fewer than 200 skeletal muscles.

Back muscles to keep you from falling forward,

abdominal muscles
to keep you from falling back.

lt takes 40 or so musclesjust to raise one leg
and move it forward.

Now, add into that running,

swimming,

shooting, riding,

and fencing,

and you get an idea of how many different
muscles are at work inside Eli Bremer,

top-seeded US Olympic pentathlete.

l think what l do is very normal and someone
will ask what a typical training day is.

And l'll tell them, ''Swim about four miles
and run about ten miles.''

You know, it's not that big of a deal.

l mean, l think anybody could do it.

And then l get this weird look like,
''You must be crazy.''

So, what propels him?

lf we zoom in on one of these muscles in motion

and closer still at the hundreds of muscle fibres
that run its length,

we find two proteins, actin and myosin.

And their actions couldn't be simpler.

They link up,
squeezing together like cogs on a wheel.

And then they relax,
releasing their grip and going back to normal.

lf during a fencing bout
Eli wants to strike an opponent

the actin and myosin in his tricep bind,

while in his biceps they release.

When he winds up for another blow
the opposite happens.

Now his biceps bind and his triceps release.

By binding and releasing
all our skeletal muscles

we get our every motion.

And 3, 2, 1 ...go!

The more we work our muscles
the more actin and myosin we make,

the bulkier our skeletal muscles become,

as Olympic hopeful Doreen Fullhart
demonstrates.

To lift, her brain sends electrical impulses down
nerves to muscle fibres

telling the actin and myosin to bind...

..and release.

But for our muscles to work,
that signal from the brain must get through.

That requires an intricate but delicate
wiring system.

(Monitor beeps)

- Have you met Dr Redett?
- Good to see you again.

Good to see you.

34-year-old Jason Keck severed some nerves
in a logging accident three months ago

and he hasn't moved his left arm since.

Just a few years ago, doctors could do virtually
nothing to fix this kind of damage.

Today Doctor Dr Allan Belzberg and his team
at Johns Hopkins School of Medicine

will try to get Jason's wiring system
working again.

The nerve is just an electric cable,
when all is said and done.

A very sophisticated one,
but nonetheless an electrical cable.

We have a nerve that's been broken,
that's been stretched and snapped.

We can bring the ends together and fix it.

lf we can't get the ends together we can fill
the gap in and splice in some material.

And if we can't do that
then again we go to this nerve transfer concept

of robbing Peter to pay Paul.

Anything? Nothing?

Paul in this case is Jason's arm.

To find a suitable Peter to rob,
Belzberg zaps various nerves with electricity

to see where current is being lost.

Not unlike an electrician checking wires
in a house.

What makes this interesting
is everybody's wired just a little bit differently.

The hope is that at least some wires
are still plugged in.

Sadly, Belzberg discovers
this isn't the case with Jason.

Just terrible.

Unfortunately, all five of the major nerves
that leave the spinal cord

that go to control the arm and the hand
have been ripped right out.

There is no connection with the brain.

So far, no-one has figured out how to plug
nerves back into the spinal cord.

The team will need to patch in somewhere else.

This looks fairly scarred in here as well.

So we do a somewhat heroic manoeuvre
where we go down

and we take some of the nerves
that normally feed the ribs,

normally feed the muscles in-between the ribs
and help you breathe.

We're using those nerves now
to eventually make his arm move.

Jason's nerves
don't reach from his ribs to his arms

so first they'll have to get extra wiring
from his leg.

So l'm harvesting the splicing wire now
from his leg that we're gonna use.

Trading what will become a scar and a numb
patch on his foot for a bend at his elbow.

lf the nerves take
his left arm's only connection to his brain

will be through the breathing muscles in his ribs.

That means with every breath Jason takes
his arm will bend.

Every breath.
That will only last perhaps six months.

Then the brain will relearn and stop doing that.

lt will take time before we know how
much movement Jason will get back.

Axons,. the fibres extending from the nerve cells
that carry electrical signals

grow about an inch a month.

Jason is receiving about nine inches worth.

So if all goes well, he'll have some feeling
and motion return within the year.

He went through a heck of an operation.

l'm sure he's going to have a lot of pain from it,
a lot of expense from it.

But to him, if this works,
l suspect it will be worth it.

Nerves to muscles -
the system is a marvel to behold.

But whether we're competing
at the Olympic level

or simply making dinner plans
and picking up groceries,

the whole thing would be absolutely useless
without an infrastructure.

Follow any muscle to its base, through a bundle
of strong, flexible fibres called tendons,

down to the very point where it's anchored

and you'll find one of the world's
most remarkable materials - bone.

Some 206 of these engineering marvels
are strewn throughout the body.

Strong enough to support up to 20 times
our body weight,

light enough to defy gravity - however briefly,

flexible enough to absorb unfathomable impacts

and connected in such a way as to provide
a seemingly endless range of movement.

Accounting for some 1 5 percent
of our body mass,

bones are what give us our shape.

(Squelching)

Without them, we would all look like this.

But despite the amazing strength and support
our inner frameworks provide,

they're usually portrayed
in a more sinister manner.

Descend 60 feet under the streets of Paris
to its catacombs hundreds of years old

and we get the stereotypical image of bone.

Dry, sterile,

white,

dead.

That's not exactly surprising.

This is the only way
most of us ever to get see bones.

And these are the only bits of us
that are going to be left.

This was the world's first glimpse of bone
inside a living human body.

The left hand of Frau Bertha Roentgen

as imaged in 1 895 by her husband
Wilhelm Roentgen, discoverer of the X-ray.

We've come a long way since then
and it turns out bones are anything but dry.

Deep in the centre of many bones,
in this tissue called the marrow,

some 1 20 million oxygen-carrying
red blood cells

and seven million microbe-fighting
white blood cells are born every minute

and shipped off to the rest of the body.

Toward the surface, specialised cells
continually lay down new bone

while others do the opposite
and whisk away old layers.

This is how bone grows with us
throughout our youth

and keeps itself strong long after we're grown.

lf we suck away all that marrow, we see bone
is mainly a blend of two substances -

the mineral calcium phosphate
and the protein collagen.

lt's a match made in heaven.

Without flexible collagen,
bone would be as brittle as glass.

Without calcium phosphate,
it would be as unstructured as rubber.

Together they're light enough to manoeuvre,

strong enough to shelter
our most delicate inner organs

and resilient enough to last a lifetime.

Go!

Champion gymnasts like Joey Hagerty
routinely push the limits of bone.

They train them to grow and adapt to extremes.

OK, Joe. Ready? Three...

Sports physiologist Bill Sands tries to ensure
this isn't past the breaking point.

Bone are living tissue like all other living tissues,
so the things we ask the tissue to do,

as long as we provide those stimuli carefully,
slowly, progressively,

we can usually get tissues
to withstand astonishing things.

lt is this adaptive property of bone that allows
a martial arts expert to punch through concrete.

SANDS:
You don't do that the first day, of course.

You have to build them up more
and more and more over multiple years.

The same goes for gymnasts whose bones
absorb a tremendous amount of shock.

Yeah, don't hook your toes.

Sands uses a variety of apparatuses
to measure this,.

like these inserts
that measure the forces on Joey's feet,

and high-speed cameras to record the impact.

Ready? Three, two, one.

Go.

Well, right here
he's over 1 50lbs per square inch.

Trust me, that's a big force.

The forces generally seen in gymnastics are
the biggest forces we've had recorded so far.

1 4 to 20 times body weight.

The unsung heroes of all this movement are not
our bones, but what brings them together.

lngenious devices called joints.

From our knees to our knuckles,

some 1 87 separate joints allow our bones
to slide back and forth,

side to side, up, down,

and round and round like a well-oiled machine.

While bones have an almost
miraculous tendency to heal,

joints are prone to break down.

Hey, Mark, how you doing?

The surgery that we're going to be doing today
is to go through...

Whether it's due to football,
weight-lifting or biking,

45-year-old Mark Kramer
has had eight shoulder operations

over the last decade and a half.

Pretty easy.

Today, Dr Carl Basamania and his team
at the Duke University Medical Center

will give him his ninth.

Number one: l hope to be out of pain.

When you live with pain every day
it makes life challenging.

(Monitor beeps)

Basamania first assesses the damage to Mark's
shoulder with an arthroscopic camera.

He discovers one of the tendons

that is supposed to hold the ball and socket joint
of Mark's shoulder in place is eroding,

causing Mark intense pain.

l can show you on the X-ray,
but the ball is sitting quite a way forward now,

because there's nothing to really hold it in place.

Basamania wants more than to simply pop
Mark's shoulder back into place.

He wants to keep it there.

And to do that he'll turn to this -

a specially engineered biological material
called extracellular matrix, or ECM,

that has the power to regenerate tissue.

Suck away the cells
from just about any tissue in the body

and ECM is what will be left.

Mother Nature's done a really good job
of bringing this material together.

Stephen Badylak of Pittsburgh's McGowan
lnstitute for Regenerative Medicine

helped discover ECM's power,

which, like stem cells, has the potential
to heal many tissues in the body.

The real magic of the material,
if you wanna call it magic,

is that this is loaded with signalling molecules

that instruct the surrounding cells and tissues
to heal in a specific way.

So if we examine...

The best part is that extracellular matrix
is found in all animals.

Pig ECM, for example,
is not that different from human ECM.

lt's not that much different than a mouse
or a dinosaur's as far as that goes.

Therefore, when we take ECM from one species
and put it in another,

it tends to be accepted as self.

We can even extract the material
from one tissue, like pig's small intestine,

and put it into another
like Mark Kramer's shoulder.

We're going to have graft, tendon
and then more graft.

This is what l refer to as a taco repair,
simply cos it looks like a taco.

Basamania simply wraps the material
around Mark's damaged tendon

and sutures it into place.

Mark's own cells will then attach to the graft

and then within weeks his own body
will reconstruct the tissue and heal itself.

For me this is very satisfying
to go from a flimsy material

to now he has what looks like
a very nice healthy-looking tendon.

Oh, he'll be back in the gym before too long.

Extracellular matrix has already been used
to grow and treat things

like the oesophagus, skin, bladder.

Even to heal the damaged dorsal fin
of a dolphin.

This idea of coaxing the body to fix itself
may offer a whole new way to treat disease.

Salamanders and newts and starfish
can regrow entire legs. Why can't we do it?

Our goal is to tell the body,
''We don't want you to just heal this tissue again.

We want you to reconstruct this tissue.''

Perhaps one day we will grow a new arm
or leg as easily as a wounded starfish does.

For now,
we're stuck with the limbs our parents gave us.

And as the sun sets on our day,

just getting two incredible machines
to reproduce at all is challenge enough.

( Violin plays a tango)

lt's a simple biological function.

The swapping of genetic material
to improve the adaptability of the species.

But getting together is anything but easy.

The seduction.

The courtship.

The commitment.

lt's all part of an intricate dance
originated millions of years ago

and choreographed over countless generations.

So why all the fuss?

Why don't humans simply do
as an amoeba does?

Just split in two.

lf all we wanted was to make exact copies
of ourselves that is exactly what we would do.

But humans,
along with practically the entire animal kingdom,

want more out of life than to simply survive.

We're built to thrive

and mixing up genes through sexual
reproduction is the best way to do it.

The dance may begin with an attractive sight.

A smell, a touch.

Soon enough the heart beats faster,
blood pressure rises.

Breathing accelerates.

Skin gets flushed.

And whether or not baby-making
is on the agenda tonight,

the baby-making machinery is raring to go.

Every second of every day,
a man produces more than 1,000 sperm.

That's 60,000 sperm per minute
or 1 4 million during the course of an evening.

They may only be about two-thousandths
of an inch long,

but 300 million are always ready
to fulfil their life's mission -

to fertilise...one of these.

Unlike a man, a woman is born with her
allotment of sex cells, about one million of them.

Only about 400 eggs will ever get released,

less than half the sperm cells
a man produces every second.

Once the egg is pushed out of the ovary
each month,

it's swooped into the fallopian tube
for about a day,.

life's window of opportunity.

lf no suitor appears the egg dissolves.

But far more interesting is what happens
when one does.

Of the millions of sperm
engaged in this genetic race

only a few will defy all the odds
and glimpse the finish line.

And as the body's smallest cells
meet the largest, only one will make it across.

There was a time just a few centuries ago,

when some scholars believed that every sperm
cell had a fully-formed miniature person inside

called a homunculus.

(Babies laugh and gurgle)

We now confidently know this is not the case.

Deep within each of the body's 1 00 trillion cells

is a complete blueprint for a human being -
a genome.

Here our DNA molecules are tightly packaged
into bundles called chromosomes.

Each cell has 23 pairs of chromosomes.

Sperm and egg cells, though,
only have half a blueprint each.

They need each other.

And during that fateful meeting, their DNA fuses,

mingling the mother
and the father's genetic traits.

For several days, the fertilised egg journeys
through the fallopian tube towards the uterus,

growing and dividing along the way.

About 20 hours after fertilisation,
it divides into two cells.

ln 48 hours, four. 1 2 hours later, it's eight cells.

And by 72 hours, it's 1 6.

Each of the new cells
is genetically identical to the original.

At this stage everything from eye
and hair colour, gender,

and even to some extent height, weight,
intelligence, sense of humour and personality,

are all pre-determined.

ln fact, scientists can even sift through
a dish of embryos to choose gender

or identify genetic defects and remove them.

But not if couples have a baby
the old-fashioned way.

By the end of the first week, the free-floating
ball of cells, now known as a blastocyst,

has entered the uterus.

Cells continue to divide here
before they find a place to settle.

lt's official,. she is pregnant.

As the weeks pass, cells start to specialise
and forms begin to take shape.

At three weeks a groove marks the beginning
of a nervous system,

the top of the tube destined to become a brain
and the lower portion the spinal cord.

By eight weeks,
almost all of the organs and systems

in this walnut-sized embryo are in place,
earning it by week nine the official title of foetus.

And now growth really kicks in.

By 1 2 weeks, just as expectant parents
get their first glimpse into the watery womb,

the foetus may practise breathing,
taking in amniotic fluid instead of air.

Already it can punch and kick.

At 1 4 weeks, it can swallow and suck its thumb.

(Woman laughs)

By 24, it can hear.

By 32, it responds to music, voices.

OK, so that's... Oh, there's her eyes.

That's eyes, nose, mouth.

Now her mouth is wide open.

And at 40 weeks, give or take,
it's ready to enter the world.

Push.

- Ten, nine. Ten.
- (Exhales heavily)

- That's it.
- Now push.

Great, great. Great, honey.

Another push.

- Oh, my God.
- There's your baby.

Good job!

22:30.

- Oh, my God.
- Good job.

- 1 0:31 .
- There you go.

Oh, my gosh.

(Air hisses)

(Cries)

- lt's a big girl.
- lt's a big girl.

ln the nine months it takes her to go from
fertilised egg to fully formed human baby

she will have grown
more than 5,000 times bigger.

As women around the globe can attest,
getting to this point is no easy task.

And yet some 260 humans
are born this way every minute.

That's 37 4,000 every day
and more than 1 36 million every year.

(Laughter)

Why evolve such a painful and risky way
to keep a species going?

lt's the price we pay for our giant brains.

Hi.

Billions of neurons
are buzzing around in that head of hers,

virtually all the nerve cells
her brain will ever need.

Throughout her childhood
they'll be reaching out to other neurons,

making more connections
with each new experience.

With each connection mind and body fuse
to form the thing that is us.

And at the helm, the most remarkable
command centre in the world.

Every system in the body is complex, but there
is only one presiding over everything we do.

Every second since our day began,

our brains have been guiding,
guarding and giving orders.

Defining nothing less than what we are.

Through an information superhighway of nerves
fanning throughout our bodies

our brains keep tabs on every part of us -

eyes and ears, skin and bones,
heart and muscles.

Through a hundred billion specialised cells
called neurons

zapping millions of electrical and chemical
signals at up to 200 miles per hour

these three-pound blobs of fat and water
let us think, feel, want, remember and react.

lt really is what makes us human,

because it encapsulates everything
from our ability to paint a beautiful picture

to construct a building,

to render violence on somebody else.

lf l transplant your heart, for example,
you're still you.

But if we do something that damages your brain,

the very character,
your very personality may change.

And so the brain is you.

And when this unremarkable-looking organ
is under assault,

everything that defines you is at risk.

Hi, Brandon. This is Dr Liau.
They're gonna be putting you to sleep now, OK?

- OK.
- l'll see you when you wake up.

Everyone in this UCLA operating room
is acutely aware of the brain's vulnerability.

23-year-old Brandon Carson
has a large cancerous tumour

near a region of his brain critical for language.

His tumour is very close to Broca's area.

(Whirring)

lt's probably one of the closer ones l've seen.

The challenge to Dr Linda Liau
and the team of doctors

is to remove the tumour
whilst keeping Brandon's speech intact.

Brandon, wake up.

Which is why once they've opened his skull
and revealed his brain

the doctors do their best
to keep Brandon awake.

Brandon, open your eyes.

The brain doesn't have pain receptors,
so Brandon doesn't feel anything,

even when they do wake him up.

- Give it a try.
- Brandon.

(Low conversation)

- No, no.
- No, you can't.

Don't sit up.

Can we do this test real quick?

DR LlAU: Language is a function
we can't map when a patient is asleep.

We can measure muscle and things like that,

but we can't really with a 1 00% certainty
know where his language areas are

unless we wake him up
and stimulate those particular areas.

OK. What's this?

Good. And this one?

Using easily-identifiable flash cards, a
psychologist tests Brandon's language capacity.

Simultaneously, Liau disrupts tiny areas of
his language centre with a mild electric shock.

Let's try that same area again.

lf Brandon has trouble recognising these
images while the shock is being delivered,

the team then knows this is a critical area
and makes sure to work around it.

Jessica, there's an area that l think is safe.

l'm going to start there
and you just keep talking to him.

By imaging the brain before and during surgery,
something she couldn't do just ten years ago,

Liau can cut out the tumour with confidence.

And with a living, functioning,
awake brain exposed,

neuroscientists get a rare opportunity
to peer inside down to individual blood vessels

and glimpse the mysterious organ in action.

Mapping the human brain is a Holy Grail -
we all want to do it.

We want to create a map
where we know what structures are where

and what the function is in those structures.

But unlike the map of the Earth where there's
latitude and longitude and so forth,

the human brain is individualised.

Each is different from the other;
it's what makes us unique.

At UCLA's Laboratory of Neuro lmaging,

Dr Arthur Toga isjust beginning to understand
these differences

with what is called the Brain Atlas.

lt's a collection of thousands and thousands
of scans of human subjects.

Various ages, various groups, various genders.

With it, we can watch a brain develop
from five years old to 90

and see it start to degrade during middle age.

Comparing a man and a woman's brain.

His may have more volume
but hers has added surface area.

Here's the brain activity of someone who speaks
one language, and someone who speaks two.

A right-hander and a left.

The Brain Atlas looks at our master organ
from a variety of perspectives,

right down to individual neurons.

Through functional magnetic
resonance imaging, or FMRl,

we can see the exact spots where conscious
thoughts originate as they form.

Navigating a map, listening to music,
experiencing fear and laughter.

This is remarkable.

You can watch the human brain function
in a normal, living individual.

FMRl also allows us to watch the brain
as it malfunctions.

Two years ago a severe car crash
left 22-year-old Kimberlee Lizarraga

crippled by pain in her neck and shoulders,
and she feels it to this day.

Just picking up groceries or driving a car
can be excruciating.

The pain that l felt was so unexplainable.
l can't even explain the pain that l felt.

lt affects my job,
it affects my whole life tremendously.

Kimberlee suffered no brain trauma in the
accident and her injuries are completely healed.

Her pain lives only in her brain.

And with the help of Stanford's Dr Sean Mackey
and an FMRl, Kimberlee is learning to control it.

Pain doesn't live in one region.

We believe it is ultimately a flow of information,
a flow of neural activity

between a multitude of regions within the brain.

What we're working on now is actually
trying to control the volume on... the faucet,

so to speak,
on information flowing back and forth.

Mackey doesn't want to stop
that flow completely.

Pain does have its place.

What's wonderful about pain
is that it's so terrible.

My son only had to touch a hot stove once
to learn not to do it.

The problem is when pain becomes chronic.

When it lasts beyond the time you would expect
for the tissue to have healed after an injury.

lt's persistent.
lt robs our soul, it robs of who we are.

All right, Kimberlee, we're going to take
anatomical images of your brain.

This is gonna take about two minutes.

Which explains why Kimberlee submits to
the confines of this claustrophobic machine.

While she's in there
the Stanford team gives her a real-time picture

of the activity in her brain's pain areas.

Represented by either a line graph or a flame.

By simply thinking about
putting those flames out,

Kimberlee is, for the first time,
putting her pain out.

The idea is to drive the activity down.

And in doing so, we also hope to see
that the flame goes down.

We still don't understand
how the brain does this.

But one thing is clear,.

we can physically change the activity
in our brains and the FMRl lets us watch.

What we showed here is that you can
actually focus on a particular region,

a particular area, and learn to control that.

And that's the first time this has been done.

This new-found power over our brains
has applications well beyond pain

to mental illnesses like depression,
phobias and addiction.

Our brains are highly malleable,
plastic, changeable.

We really can control and change our brain.

And so the opportunities are truly limitless,

because there's no area of the brain
that we can't now tap into

and have somebody learn how to control it.

What's news to neuroscientists has been
practised by others for thousands of years.

Using nothing but simple meditation, some of us
have already learned how to control the brain.

Our brains enable us to do extraordinary things,

but some are much better than others
at harnessing its power.

Buddhist monks have used their brains
to dry wet sheets on their backs,

slow their heart rates,
or be incredibly resistant to pain.

For Souei Sakamoto, a Shingon Buddhist,
it's meditating half an hour a day

under a frigid waterfall in Toyama, Japan.

A ritual that dates back hundreds of years.

(Speaks Japanese)

TRANSLATOR:
We have an old saying in Japan;

''Clear your mind of all mundane thoughts
and you'll find that even fire is cool.''

When you learn to control your brain
it may be possible to use the brain

to influence the body in very unusual ways.

To understand the brain's power

Richard Davidson
of the University of Wisconsin-Madison

studies the effects of meditation
on Buddhist monks.

Specifically, measuring how their ancient
practices physically change their brains.

These are individuals who we can think of
as the Olympic athletes of meditation.

They have spent years cultivating
certain qualities of mind

and they are virtuosos in many respects.

This is just to keep any water that might drip
down from getting on your clothing.

- Oh.
- A little bit of water might drip on you.

East meets West in Davidson's lab

as FMRls, PETscans
and electroencephalograms, or EEGs,

which involve this unusual contraption,

are all aimed at monks deep in meditation.

Today it's 84-year-old Geshe Lhundab Sopa,

who's been an ordained Tibetan monk
since 1 932.

You have an interesting new hat, Geshe.
You look very futuristic.

By attaching these 1 28 wire-laden sponges
to Geshe Sopa's head,

the Wisconsin team can record
the tiny electrical currents

that continuously emanate through his scalp.

A measure of the millions of neurons firing away
in his brain at any given moment.

He'll begin with a traditional
compassion meditation.

So we'll begin in the neutral state, Geshe,

and l'll let you know when to begin
the compassion meditation.

Experienced meditators can enter a deep,
meditative state in less than 20 seconds

and with the EEG we can watch as it happens.

Compassion, compassion.

Just at the start of the transition
when a practitioner begins to meditate

there is a very discernible change
in these brain signals.

And together with FMRl data,

Davidson has located these changes
in several areas of the brain

including the prefrontal cortex.

So this is an area here
that is in the left prefrontal cortex,

that we find more activated in the practitioners,

particularly when they're generating
this compassion meditation.

Left activity in this region is associated
with enthusiasm and happiness,

right with negativity and stress.

By meditating these monks are able to shift
their neurons'activity from right to left.

DAVlDSON: These changes are changes
that have not been seen before

and so this opens up whole vistas
of new possibilities

that we're only just beginning
to scratch the surface with.

Already, Davidson and others have found
that meditation's effects on brain activity

can lower levels of stress hormones
and boost immune function.

And for as little as two minutes three times a day

he believes even those on a much lower plane
of enlightenment can reap these benefits too.

Whether we control them or they control us,

our brains more than anything else
set us apart from all other species,

and one another.

But thought, feeling and selfhood are fragile.

Though it's only about 2% of our body weight,
the brain exhausts 20% of our oxygen.

lf the brain is without oxygen for
just ten seconds we lose consciousness.

Four minutes,
and the damage can be permanent.

And unlike other cells in the body,

when neurons get badly damaged
they cannot be replaced.

WOMAN: (over speakerphone) OK,
this is the result for patient Carson, Brandon.

For section No.1 left frontal tumour,
the diagnosis is...

At UCLA Dr Linda Liau continues to work
on 23-year-old Brandon Carson.

After mapping the speech areas of his brain,
she's ready to remove a cancerous tumour.

That darkened mass, yes.

What l'm trying to do is dissect around it.

As an electronic scalpel cuts into his brain
Brandon is still responding to those flash cards.

Not a scrap of cancerous tissue can stay.

And just the tiniest sliver of brain
can be removed.

There's some deeper parts of the tumour
that are near blood vessels,

and, obviously, we don't want to take out
any necessary blood vessels.

The only way we could see that
is through the microscope.

This is the hole where the tumour used to be.

Thanks to these new real-time glimpses
into the brain

Brandon will soon wake up from his surgery,
tumour-free and speech intact.

We inch one step closer to understanding
how it all works

and how far we still have to go.

l think that as you learn, you know,
where vision is

and where l control my hand from
and where my speech is located,

you begin to feel like,
''l'm understanding this circuitry.

l think l understand how the brain works.''

And then you get into it a little more deeply

and you realise you don't know very much at all.

That the wonder of the human brain is sort of
one of these great frontiers. That's the truth.

The more you learn
the dumber you realise you are.

The same applies to all parts
of the incredible machine.

Whether it's our control centre
or pumping station,

our security or exhaust system,

our power plants or copying machines,

the human body has been a marvel
of complexity for more than 1 00,000 years.

From its surface to its core,
amongst its trillions of cells,

and throughout its roadways and circuitry,

at the end of the day,

somehow all of these systems converge
into one truly incredible design.

Even while we sleep, our bodies are always
working, always breathing, always beating,

always ready to begin another day.

And though there may be an infinite number
of species born of stars long gone,

we can all rest easy knowing there is nothing
quite like the incredible human machine.