Anatomy for Beginners (2005) s01e01 Episode Script

A 55 year old man,
who made an extraordinary wish before he died
that his remains be used by me
to educate people about human anatomy.
I met him several times.
He was passionate about science
and about the enlightenment of lay people.
Tonight, I will dissect him
and unravel the mysteries beneath his skin.
LESSON ONE | MOVEMEN
Wiggling your toes
it seems an almost inconsequential action,
yet the systems that underlie | it are amazingly complex.
In this series,
we will be revealing the | systems of the human body
so that you can see them for yourselves.
And in this programme, we will | be beginning with Movement.
We will be taking you to | the core of the human body,
to the central controllers of | the brain and the spinal cord.
And how they are connected to our | movement machines - the muscles.
And how the muscles transfer their energy
to the system of levers which is our skeleton.
But to get there, we first-have to peel away
the part of human anatomy that is most familiar.
Dissection has been done since centuries.
This picture originates from 1747
and the approach is always the same
at first we have to take off the | skin to look at the muscles.
And to dissect those,
I go over here to our specimen, | which is in upright position,
because this is the position | we move our muscles.
For reasons of anonymity,
I have covered the face.
We want to start from the back,
therefore I want to turn around.
Marius, could you be of help, | thank you very much.
To take the skin away takes a while,
therefore we have already started,
so we are faster.
And I start here.
It's a side and I want to take off | the skin in one large piece.
This is a fresh specimen
we have not fixed it.
This way, the muscles are more flexible,
it is easier to show you, | later on, their function.
If you think of the skin as an organ,
the skin is actually our | largest continuous organ.
I think you will be surprised | at just quite how big it is
when it has actually been fully removed.
The skin forms our interface | with the external world.
It has a number of functions:
it conveys sensory information from the | outside world to our nervous system;
it is responsible for heat regulation
because the sweat glands | are located in our skin.
The skin also makes specialised | structures such as hair and nails,
and although it is a continuous organ,
it does have specialised areas,
for example only our scalp tends | to make hair in profusion,
only the skin near the tips of our | fingers and toes makes nails.
Although the skin itself, when it is removed | in this way is a very large organ,
a lot of the material that you see is | actually composed of tough, connective tissue
and subcutaneous fat,
which also helps to keep us warm.
But the actual active portion of | the skin is a small growing layer
just between the fat and connective | tissue and the surface,
which is what rubs off | when we are in the bath.
This layer is only a single cell thick
probably about a 10th of a millimetre thick,
and thinner than a piece of tissue paper
and as easy to tear or probably easier to tear.
But without that growing layer,
we wouldn't actually have a skin to protect us.
I want to save the ear and the face.
So the skin is loosened and I actually | take it now with scissors off the body.
Would you help me a little bit?
The hand, hold it please.
The colour of the subcutaneous fat that you see
is exactly the same as a Surgeon sees | when he is doing an operation.
Actually, the skin,
the largest organ,
depending on the amount of subcutaneous | tissue between 3 and 30 kg heavy.
You want to put it neatly, you know?
This was very important that | the specimen looks nice.
This now is the skin in its entirety.
Here, the skin from the head.
The right and left extremity is here the leg.
And in fact, although this | may seem, and indeed is,
a very strange sight
it has a long history in art.
One of the most famous examples of | the skin being painted in this state
can be found on the roof of the Sistine Chapel,
where Michelangelo has painted a portrait of | himself as the flayed skin of St. Bartholomew.
To give you an overview about the muscles
they are all covered by loose, connective tissue
the muscle sheaths, and inside | the muscle contracts.
Over the trunk, they are the | muscles in a flat shape.
They move the shoulder blade,
they move the rib cage,
they move the hips,
but, as for the extremities
the muscles always have a rather round shape
and they usually end in tendons | in dense, connective tissue,
like here in the lower arm, | or like here in the biceps.
Well the logic of dissection means that | we must start our study of movement
from the outside, with the muscles.
So let's first have a look at | some muscles in action,
and over here we have Juliet, | our resident anatomical artist,
who is just drawing some muscles | on our model Dennis's arm here,
which we will come to in a moment.
But first let me show you a muscle in action,
and if I could just ask you to hold that for me,
I will swap it with a ruler,
and Dennis here has a particularly fine biceps
that we can do a useful demonstration | of muscle action on.
If you just hold your arm there,
and I am just going to extend this ruler
and if I put the end of the | ruler near the one there,
at the end of Dennis's biceps.
If you now tense your bicep Dennis,
you can see that bulge - it shortened | really quite considerably.
Just relax again, OK.
Let's do that one more time,
so there it is and the muscle has actually | shortened about half of its length.
Thanks.
Well, it used to be thought that
muscles were some type of spring
and that they pinged together | when they shortened,
perhaps the proteins coiled up.
But, in fact, the modern understanding of | muscle was only established in about the 1950s
when it was found out using electron microscopy
very high magnification microscopy ,
the muscles really are constructed | like little machines.
They are made out of interlacing | filaments which overlap in this way.
And when the muscle is switched on,
actually via an arriving nerve impulse,
this causes the filaments to interact in such | a way that they slide past one another,
and when the muscle is switched off,
they then relax again.
So muscles really are constructed | like a small machine,
which moves past and back and past and | back in shortening and lengthening.
Well, if we now have a look at the muscles | that Juliet has drawn on Dennis's forearm here
we have mentioned the biceps | in the top of the arm.
Muscles can, of course, only contract.
Which means that for every group of muscles,
there has to be a group of muscles | on the other side of the bone
to pull in the other direction.
These muscles here, this package of muscles
is the group which extends the wrist, | it bends the wrist back in this direction.
If you just contract those | muscles there for us Dennis,
you can see the muscle groups here and the | tendons running down into Dennis's wrist.
We are now going to have a look at these | groups of muscles in our dissection specimen.
To show you this on the specimen | now we have to turn it around and,
okay here are the biceps which we | just demonstrated in the live model
and here you see the lower arm,
and this is a flexion and this is extension
and so it is actually the muscles on the | lower arm which moves the hands.
It is like a puppet show,
otherwise there would be too | much muscles on the hand.
All the small tendons going here, only | a few muscles at the hand itself.
So I want to demonstrate this by taking | off the flexor muscles of the hand.
For that I have to cut off the | flexor muscles of the lower arm,
which originate here from the | medial part of the lower arm,
so I just do that.
When I pull here,
one moment, give me the knife again.
I need to do this also to the periphery,
and you will see in a moment that, indeed,
the muscles go forward, this takes a moment.
There is actually a large band | of connective tissue to avoid,
its normally the tendons move out,
and I have to open this canal.
And then I am able to take the muscles out.
All of our muscles and tendons are | constructed around our skeleton.
Our skeleton is the central strut and | force-transmitting tissue of the body,
composed of bone.
And the area that we are looking at on | the dissection specimen at the moment,
is the tendons running into the hand | and the bulk of the forearm muscle,
mass of muscles, here.
The tendons themselves actually | form a firm join with the bone,
which transmits the force from | the muscle to the bone,
causing movement of the bone at joints.
What I open, here, is a | so-called 'tendinous sheath'.
It is actually the bed where | the tendons move to and fro.
That's right, one of the important things | about muscles and tendons is that,
throughout our lives, they have to be | able to move and slide over one another,
and not get stuck to either themselves | or other structures.
So muscles are all contained | within their own bags
and the tendons also contained | within their own sheaths.
Sometimes, indeed, you get inflammation | of the tendon sheaths called tendonitis.
And that can actually cause a painful | sensation in the area affected by it.
So as you see, the tendons actually | take a quite complicated pathway, here
and when I now pull the | muscle of the lower arm,
the tendons actually are tight | and the hand is moving up.
And you can imagine how much fine movement | must be exerted by the nervous system now.
For example, when playing the violin.
That's a very striking demonstration | of the way we really are constructed
according to mechanical principles.
There is actually a way you can | demonstrate this as well, for yourselves.
If you hold your middle finger in | the position that I am showing here,
you will find that you can't actually | move the bottom part of your finger.
That's because you have actually lengthened | the tendon across this joint here,
and the muscle now has no pull,
so you find that that will be immobile whereas | obviously when you straighten your fingers,
the fingers can move again.
The extensor muscles of the | hand originate out here,
mainly from the back of the lower arm.
All the tendons are, again,
together with the muscles | in sheets of very soft,
connective tissue, which I would | need hours to dissect fully away.
But what is important for me | to show you is the function.
The ulna is the bone in the forearm which runs | along the side nearest your little finger.
It's probably worth pointing out | while this is just continuing,
that muscles can only contract.
So, wherever you find a group of muscles,
you will find an opposing group of muscles.
If a joint moves one way, it has to have another | group of muscles to move it the other way.
So the muscles that have just been demonstrated | on the palm side of the forearm
are called the flexors because | they bend the hand forward.
And an opposing group of muscle is | found on the back side of the forearm
called the extensors
and they are used to move the | hand in the opposite direction.
You can actually now see the mechanical | struts of the forearm revealed here
the ulna on this side and the radius | on the side nearest the thumb.
In anatomical lectures in this | section course for students,
this takes about a day to do,
but I do here in a few minutes.
So, this is all connective tissue | which you have to remove,
So I move not only the finger, | but I also move the wrist.
It's probably worth pointing out that | there are also some small muscles,
in fact, quite a large number of | small muscles within the hand itself,
and these are mainly used for | the very fine movements.
And there are all the connects and bones | together to pad, actually, the palm.
For that reason, we have on the palm-side | more muscles than on the upper side.
By now we understand a very | important construction feature
of the muscles of the extremities.
The fingers are moved by | muscles of the lower arm.
The lower arm is moved by the | muscles of the upper arm
and the upper arm is moved by the muscles | of the shoulder girdle of the scapula
and the same holds true, here for the leg.
The upper leg is moved by muscles on the | buttock and within the abdominal cavity.
The lower leg is moved by muscles, | here, of the upper leg,
primarily by the largest muscle | of the human body,
which has four heads just in front of the thigh,
which is called quadriceps femoris.
And I want to show you this | muscle by demonstrating,
use the fascia - the connective tissue sheets,
where the muscle actually lives in and moves in,
and, here very nicely, you can see now
I actually can go with a hand inside,
between the muscles,
between the muscle and this fascia | which actually are the supporters
and so to expose the muscle in full,
I show it all down to this bone,
which is the patella,
and it serves for moving the power | across the joints, the knee joint,
to the lower leg.
One of the unique peculiarities of being | human is that we walk on two legs.
And this means that whereas | the bones in the upper arm
can be fairly slender and the muscles can | be small and deal with fine movement,
the bones in our two legs have to | transmit all the force to the ground
and the muscles are very large.
And we can see the point about weight | bearing on our skeleton over here.
If you compare the size, for example, | of the humerus in our upper arm
with the femur in our upper leg,
you can see that the femur is substantially | greater than the humerus.
And if you could just pass me, | we have got over here, thanks.
Our bones are often taken to | be dead, inert structures
because we tend to see them in | preserved skeletons like this,
but in real life, they have a blood | circulation going to them
and they are constantly being remodelled
to take into account the stresses and | strains that are falling on them.
And we can see this very clearly in | a bone like this - this is a femur
that we have been able to bisect.
And if I open this femur up here,
you can see that it has a really | quite striking internal structure.
I'm just going to put one half down.
And you can see that the bones are actually | constructed a bit like a box-girder bridge
there is a thick, outside layer | called the cortical bone
and inside there are numerous fine | trabeculae of trabecular bone.
And these small, strands of bone
serve to transmit the forces from | the outer layers of bone,
through into the other area, outer layers | of bone, and maximise the strength of bone.
The point of this is to have the maximum | strength for the minimum weight,
so we don't carry too many | bones around with us.
And these little trabeculae are constantly | being remodelled throughout life.
Another feature we should draw | attention to at this point, is our joints,
because our joints are necessary for the muscles | to be able to move the bones on one another,
and I can demonstrate some aspects | of joints for you using this pelvis.
First of all, the bones had to be | very carefully held together
and the structures that do this are ligaments.
Ligaments are these very, very | tough connective tissue sheaths
that extend from one bone to another bone.
They are tightly bound to the bone at each side,
so that the bones can't come apart.
And indeed if you fall awkwardly or | pull your bones awkwardly,
a rip in one of these ligaments or a strain in | one of these ligaments is known as a sprain
a sprain is when you actually damage | the ligamented sheath of the bones.
In real life, bones are capped by | special structure called cartilage.
And cartilage forms the interface | between one bone and another bone.
It is the glistening gristle that | you see on bones in meat,
but it has a very important structure, it is | also constantly remodelled during life.
And particularly important for the purpose | of especially weight-bearing joints,
it is self-lubricating.
When one set of cartilage presses | on another piece of cartilage,
a tiny amount of the fluid inside the | cartilage comes onto the surface
in a similar way to the way an ice skater is able | to skate over the ice on a thin film of fluid,
so the cartilage actually glide over | one another on a thin film of fluid,
and damage to this cartilage is particularly | important in a condition for example,
osteoarthritis,
where the cartilage gets damaged and the bones | begin to grind directly onto one another,
which is extremely painful and | causes distortion of the bone
and limitation of joint | movement and is, in fact,
a very important cause of illness in our | society, especially in elderly people.
The patella tendon here that is being exposed | is one of the biggest tendons in the body
and these very large tendons often develop | what are called a special type of bone
a sesamoid bone
within them and the kneecap or patella | is the biggest such bone in the body,
and the idea of this bone is that it is located | in the middle of this very big tendon
to give added strength.
This moment is a real anatomical highlight.
We see here on the end of | the femur with its cartilage,
we have opened the knee joint and | here are the crucial ligaments,
here are both of the menisci on | the outer and the inner side,
and here is the patella tendon going to be | kneecap and here the large quadriceps muscle.
Now, let's take action,
I flap it back and when I pull here,
Again.
The individual parts of human | anatomy are surprisingly heavy
when they don't have muscular | power of their own,
so it's actually quite difficult | to pull, with your arms,
the lower leg, even though our quadriceps | muscle in the thigh, manages it with ease.
There are so much more muscles, more | muscles than I have in both of my biceps.
Therefore I have a hard time to | move the lower leg in front.
While let's just remind ourselves | where these muscles are,
over on our live model.
If I could just turn Dennis round again, here.
Juliet has drawn the quadriceps femoris | in the front of the thigh here,
going down to the patella,
which you can demonstrate moving for yourself | by flexing and extending your leg.
And then another group of muscles | has been drawn, here,
in the anterior compartment of the lower leg.
These are the muscles which flex the foot and the | tendons can be seen there, going into the foot.
Well, we have seen quite a | lot about muscles now,
we have figured out roughly how they work,
we have seen how they are attached to bones
and how the bones move on each other,
but what controls all this activity?
Well, the central controllers are | the brain and spinal cord,
and they are buried deep inside our bodies,
and that is what we are | going to have a look at next.
The next what I have to do | to turn the body around,
because all the muscle actions they | are actually commanded by the brain,
so we have to expose now, the brain.
We have pre-dissected it to a certain extent,
and I have to go a little bit up,
and I cut through the skull.
Well, it looks a little bit gross,
but in the whole world, they do it every day
all anatomists, so
There is no other way, you know? To go inside..
And that is cut, oh, I already see the brain.
I am sorry, one moment later you will see it.
I go to the other side..
The brain is a difficult organ to expose,
because it is hidden away inside | a bony case, the cranium,
and the reason for this will become apparent | just as soon as we have managed to
take the back off the cranium | here and expose the brain.
I need a little bit more of the saw, | we didn't pre-saw sufficient.
Yes, this should make it.
I go through the bone, | through the base of the skull.
I have to be careful and | strong at the same time,
because suddenly it may fall down and | then what happens with the brain?
The brain has a consistency of | blancmange and when I touch it,
it is elastic and very soft.
So what I do now, because we want to show | the brain and the spinal cord as one organ,
I'll put it back, put it in the | same natural condition.
And now, I like to show you the consistency | of a brain in a simple experiment.
We have actually prepared a blancmange
and it has, remember, exactly | the same consistency.
And when I drop it down here,
up to 200 million nerve | cells will look like that.
Well, the brain may not look | like much from the outside,
and it may have a very soft consistency,
but internally it is actually | a miracle of organisation.
The brain is composed of | about 10 billion nerve cells
and you can see one or two of these on | this rather beautiful micrograph here.
This is actually prepared by a technique
that only shows about one in 50 or | one in 100 of the nerve cells
present within a given volume of brain.
These little black dots that you can see here,
are the nerve-cell bodies,
the little wiggly lines coming off them
are the dendrites and axons - | the processors of the nerve cells
that ramify throughout the nervous | system and interconnect with one another.
An individual nerve cell may have | up to 10,000 different branches,
so you can imagine when you have this number | of nerve cells interconnected in this way,
that the brain has an astonishingly | detailed organisation inside.
And it is why the brain is so difficult | to repair if it gets injured
the fine structure is such that we | could hardly hope to intervene.
This is a brain which has been preserved by | immersing it in a substance called formalin,
which firms up its structure.
The human brain is a truly remarkable organ
it is no exaggeration to say that it is the | most complex object in the known universe.
This is the organ through which | we see, hear, feel, love,
in fact, perform all of the functions | that we are aware of,
and indeed, many that we are not aware of.
Let me show you very briefly, some of | the key features of the human brain.
It sits in a head like this.
The area, here, towards the side
is an area which was first identified as | having a speech-function, in the brain.
The area in the back of the brain, here,
is the area that is responsible | for processing vision.
The area at the front of the brain, here,
is involved in our personalities.
The cerebellum, the little brain sitting | underneath the brain, here,
is involved with motor learning | and motor coordination.
And underneath the brain,
you can see the brain-stem running down here,
which is responsible for a lot of | automatic functions of the body,
like breathing, and circulation.
Well, let's show you inside the brain | in a little bit more detail now,
and we can do this by slicing it open.
And I want to slice it professionally,
and therefore I need assistance and will do it | with a machine you may have seen before.
I will now cut the brain in one centimetre | slices in the frontal plane.
It is injected.
Therefore you see here, inside,
white matter
and grey matter.
Now, I go to two centimetres of slice.
And it actually here you see | down the spinal cord,
so I
order it
in consecutive order
The human brain has been studied | intensively for over 150 years
and there is still so much about | it that we don't know.
But is probably worth pointing out one | or two features on these brain slices.
First of all, if you look closely here,
you can see that there is a rim running | round the outside, the cortex.
And a medulla, a white area in the middle.
It is in the cortex that most of | the nerve cells are found,
whereas the fibres running from them are | mainly found in the white matter, further in.
This band of white matter here, running | from one side of the brain to the other
is known as the corpus callosum,
and it is through this that information travels | from one cerebral hemisphere to the other.
And finally, this area, here, shows | part of the basal ganglia
and you can see some white matter | and running down through it.
This is the tract which takes | most of the information
directing movement from the cortex | down to the spinal cord,
and it is in this area that a large | number of strokes happen
that is part of the brain dies when | its blood supply is interrupted
which is why strokes are so commonly | associated with paralysis.
Well, let's follow our movement order now
from the motor cortex of the brain,
through the internal capsule | and down the spinal cord.
And to expose, now, the spinal cord,
I have to open first, the | spinal vertibral column.
And just while this is happening,
we can show you over here | on a plastinated model,
the organisation that you can | find at the back of the body.
You have already seen the brain,
you have seen the brain stem | coming down from the brain,
and the spinal cord is hidden away in | the protection of the vertebra
running in a canal, right through | the middle of the vertebral column
that is what is being exposed now | on the dissection specimen.
What I do now, I have a flap here.
The muscles, the so called | erector of the trunk,
is quite thick here, I flap it back.
In order I have easy access | to the vertibral column,
to expose the spinal cord.
What I have actually to take away | are the spinious processes,
and for that, I have to saw from both sides.
It's often thought that the spinal cord
is just a connecting trunk between | the brain and the peripheral nerves,
which take the nerve impulses out to | the limbs and the rest of the body,
but in fact, the spinal cord is part | of the central nervous system
and an impressive amount of processing of the | descending motor impulses that help you move,
actually happens within the spinal cord, itself.
These are the spinious processes,
which we don't need now any more.
And they are just covering up here,
the spinal cord in its dural sack.
I will now cut the connection between | the brain and the spinal cord, here.
And having seen the degree of structure | that there is within both the brain
and, by implication, the spinal cord,
you can understand why it is so necessary | that the spinal cord has to be protected
within this bony sheath,
because it is a very, very delicate structure
with an enormous amount of computing | power buried within it.
Well, what I cut off now on both sides,
the nerves which, like telephone lines,
go to the right and left in with | the body along the rib cage,
to the arms and down to the leg.
And from the vertibral canal now,
I remove the spinal cord in its dural sack.
This is connective tissue and what I cut | off from both sides are the nerve roots,
which go into the whole body to both sides.
So I now have already reached | here, the lumber region.
Go-ahead. Marius would you help? | Thank you.
The organisation of the spinal cord
preserves a memory of when we | used to be much simpler creatures
maybe a wormlike creature.
And our bodies actually divided into segments,
with the nerves coming off
paired nerves coming off at each level,
supplying those segments.
The spinal cord is also organised in segments,
which gives information out to | the various body segments
both the muscles in those body segments,
and the sensory impulses coming back.
The spinal cord, although it is | protected within the vertibral canal,
is clearly is susceptible to | injury if the back is injured.
And clearly, if a complete transection,
that is a complete cut across | the spinal cord occurs,
then the individual will be | paralysed below that level,
and will also not be able to feel | anything below that level.
About at the point we are at now, | is the nerves to the leg.
It may be worth just saying that | the actual spinal cord
finishes higher up in the vertebral | canal than people often think.
It actually finishes in the small of the back,
and much of the rest of the vertebral canal | is occupied by leashes of nerve fibres
running down towards the lower limbs.
Which you can very clearly see here, | because these are all nerve fibres, you see.
That's right, and we are never going | to follow the longest of those down
to take us back to our wiggling toes.
Cut this, please.
So the end, you see it very clearly,
the end of the spinal cord is here | and all of these are now nerves,
and we follow the largest one through | this sciatic nerve at the back of the thigh.
Therefore, I have to remove | now the gluteal muscle.
The spinal cord contains tens | of millions of nerve fibres.
So, every minute of every day,
there are tens of millions of signals | passing down your spinal cord
to connect with motor neurons | which move your muscles,
as well as many other tens of | millions of sensory impulses,
coming back towards the brain.
It is an amount of computing power
that is actually equalled by | nothing else that we know.
Well I have to remove here, | now part of the sacrum
because within the sacrum | the plexus runs down.
I continue now to take
the spinal cord, or better to say,
the nerves at the end of the spinal cord, out.
The initial little roots that come out of the | spinal cord contain either motor movement,
fibres - those that come out of the front,
or sensory fibres for those | that come in at the back,
but the peripheral nerves which | we are now coming down-to,
contain both mixed motor and sensory fibres,
which is why a nerve injury usually produces | both mixed movement and sensory symptoms.
So, what I actually removed is the | sacrum in parts of the bone.
And I was, too, careful - I cut | the nerves on the right side.
Here, I expose the rectum, the | large intestine from behind.
So, put it all up please, here.
And we are now already down here, | the sciatic nerve, here,
and you go all down, so you see.
Within the sciatic nerve, you | see the different nerve fibres.
If the central nervous system, | that is the brain and spinal cord
and are the main central processors,
the peripheral nerves are the wires that | connect these central processors to the muscles.
The peripheral nerves take movement | signals down to groups of muscles
to induce a particular type of movement,
and they also take sensory feedback,
which allows us to continuously | monitor what we are doing.
We follow the nerve down to the toes,
cutting off the muscle branches which | innovate the muscles of the calf.
Then take the nerve all out of its bed,
all the way down and now we are | already down here, at the ankle.
So I cut off, now, the nerve that comes | to the last muscles of the toe
and now I take it all out from the top.
I take the spinal cord out of the vertibral canal,
take it out here, the spinal plexus,
sciatic nerve, peripheral nerve | and all down to the toe,
and I bring it over here.
And I need some assistance now.
I don't need this machine any more, could | you bring it away, Nadine and Marius.
down to the toe.
Well, let's try and give you an idea | of the staggering complexity,
as well as the real beauty, of | our nerve-fibre network.
If I just come over here to our live model
and if we could just begin to | take the lights down, please.
So, here we have projected onto Dennis's back,
a model of both our central | and peripheral nervous systems.
And so we have finally been able to | show you the full journey of a thought
which started with wiggling | the toes up in the brain,
passed down the spinal column,
into a leash of nerves passing down the legs
and was then able to give the | muscles in the front of the leg,
the signal to wiggle the toes.
A movement which seemed inconsequential,
but which I think you will now agree,
has an amazing complexity behind it.
Now we have time for some questions please.
Once the heart stops to beat,
how long does it take before | brain cells begin to die?
The brain is actually the most sensitive | organ in the body to lack of oxygen,
and it starts to die within a minute.
Next question please.
Sometimes when we get a pick feeling in our | skin we say that it is a 'nerve ending'.
Is that really a nerve ending, or is | it just some sensation in the skin?
If you get a sensation of pins | and needles in the skin,
it's because a lack of oxygen to the hand, say, | because it has been in a funny position,
causes the nerve fibres to fire-off | and we feel that as a sensation,
even though it is only actually | originating from the nerve fibres.
Next question.
I know you said at the start you did | some pre-stuff to get the skin off.
If the person had had more fat, would it | have been harder for you to get the skin off?
When the person would have more fat,
I would need much more time | about five times as long.
One more question?
When the spinal cord was severed,
it reminded me of when | Christopher Reeve broke his neck.
Now, in doing so, all of the muscles,
I mean, he broke his neck, so that | just severed everything for him, right?
As compared to some people who are | paraplegic so have some movement?
Very important is the head.
When it happens up here,
it is quadriplegic and nothing moves any more,
perhaps he can open the | eyes and close the eyes.
When it goes down here,
then he cannot move his leg | any more is a paraplegic.
So it depends very much on the head and only | on the cut or the damage at the spinal cord.
Let's assume our model now decides | "I want to wiggle my toe".
The command starts here | in the cortex of the brain,
runs down, through the spinal cord,
down the sciatic nerve to the toe.
And to demonstrate to you this,
at our model, I like now, please, | assistance to go over to our model.
Dennis, thank you very much | for presenting yourself.
So, what actually happens.
Because we did at the same side.
Dennis' brain, spinal cord
and could you follow it exactly right to the | toe, you see the length is absolutely proper.
And this is the summary of our programme,
when Dennis - shown here in the rear specimen,
decides to wiggle his toe | it goes from this brain,
as you see it in this section, | down the spinal cord,
down the nerves, into the toe,
so he can wiggle it, please.