- [Voiceover] The central nervous system really is only
made up of two things:
The brain and spinal cord.
Now obviously the brain and spinal cord
are very important for the body.
So you have several different ways of protecting it.
You have a bony protection around the brain, your skull.
You have a bony protection around the spinal cord,
your vertebrae.
But you also have these meninges.
These are membranes that cover the brain and spinal cord.
They're called the dura mater, arachno mater and pia mater.
They're meant to give extra protection, extra nutrients
to the brain and spinal cord.
Pretty much ensuring that it stays healthy.
But then we also have this cerebrospinal fluid.
The cerebrospinal fluid is to be found around the brain
and spinal cord as well as within the brain and spinal cord.
It acts like this shock absorber in your head.
That's why if your head also moves forward,
you don't get a huge headache right away,
because your brain didn't bounce off
the front of your skull.
But in certain cases, maybe in a car accident,
also when your head really smashes forward quickly,
or a roller coaster and your head all of a sudden
snaps to one side,
the brain can actually bounce off of the bone.
Sometimes it might give a little feeling of disorientation
or a headache.
And all of the cerebrospinal fluid is meant to protect
by cushioning, but also providing nutrients.
And all that fluid is made right within the brain
in these open spaces called ventricles.
We have this blood-brain barrier.
Now the blood-brain barrier is actually
a network of blood vessels.
Capillaries, to be precise.
These capillaries are trying to prevent chemicals
and pathogens and basically items that we don't want
in our body from getting into the brain.
So here we have a picture of the brain
and a truncated view of the spinal cord.
So you're looking at,
can see all the hair, the scalp, sure it's still protection.
Helps keep the sun, helps keep the elements
out of the brain.
We have the skull.
Nice, solid, bony encasement.
We have meninges, dura, arachnoid, pia mater,
all forming different layers around
the central nervous system.
When you get through that, the very bottom
is where we hit the brain tissue.
Now all the blue coloration you're seeing here,
that's where the cerebrospinal fluid is located.
You can see how it encases the entire outside of the brain.
The entire outside of the spinal cord.
But it's also found within.
So that is your cerebrospinal fluid.
Now as far as the cerebrospinal fluid production.
They're produced in the ventricles.
You can see in the bottom left you have this anterior view
or view from the front of the brain.
You have a right and left ventricle.
But you also have a third ventricle, which is right
in the dead-center of your brain.
And a fourth ventricle, which is a little further down
towards the spinal cord.
All four of these ventricles are fluid-filled spaces.
So the fluid is your cerebrospinal fluid.
It's being produced in these open spaces.
The spinal cord really is an extension of the brain.
It's a way of getting information out of the brain,
but also a way of getting information back into the brain.
Pretty much functions like a superhighway.
It conducts some of the fastest speeds for action potentials
there are in the body.
The signals can fly up and down the spinal cord.
It's made up of two different types of matter.
A white matter and a grey matter.
Now the white matter is the outer portion
of the spinal cord.
It's where you have all the myelination.
It's where you have all that insulation.
You're gonna have both your sensory and motor tracts here.
So this is how the information goes up
and down the spinal cord.
The grey matter, well that's more at the center
of the spinal cord.
In this location, it's not really relaying information
up and down the spinal cord.
It's how the information gets into the spinal cord
and how it leaves the spinal cord.
You have all these cell bodies and neurons and dendrites.
Are all coming into the grey matter
from throughout the body and then leaving the grey matter
to go to the body.
So white matter going up and down the spinal cord.
Grey matter allows information into
and out of the spinal cord.
So here we have a view of the spinal cord.
You can notice, if you look in the middle
at that picture b here.
You can see how the vertebra actually encases
the spinal cord.
It forms a bony protection all the way around it.
While taking the majority of the weight on the
actual body, that main chunk of the vertebra.
If you go up to the top right, you can see there's a cut.
A transverse slice.
Imagine that someone took the spinal cord running from
your neck down towards your torso and cut right through it,
creating a top and bottom half.
This is what it looks like.
You can see the white matter around the outside
and the grey matter on the inside.
You can see a hole on.
That grey matter's not really touching the edge.
That's true.
The neurons will actually run through the white matter
to get to the grey matter.
So the brain itself.
It really is your command center.
Even though your spinal cord can have spinal reflexes,
it can make certain decisions on its own.
Even when a decision is made, it still tells the brain
what it did.
Now there are three major divisions.
One is called the hind brain.
And this one is dealing with basic coordination,
automatic control, vital tasks.
Things that you don't even think about.
They just happen.
You have a mid-brain.
Now this is coordinating your muscle groups.
When a sight or sound occurs around you,
this part of the brain will react to that sight
or react to that sound.
And then we have this fore-brain.
The fore-brain is meant to receive signals.
It's meant to take that sensory information
and integrate it, to put it together,
to understand what's going on.
It helps you to determine or create your complex behaviors.
Well if you're thinking, "Complex behavior, what's that?"
The simple act of grabbing a glass of water
and bring it to your mouth and drinking
can integrate dozens of muscles all at once.
Plus continual visual feedback.
So you know it reaches your mouth.
Plus touch receptors on your fingers to apply
the correct pressure to the glass so it doesn't slip
or isn't crushed.
Plus the muscles in your throat to swallow.
I mean, the list goes on and on.
Almost every action we do is a complex behavior.
We're looking at right now, is a
picture of a human brain.
That is a real human brain, not a model.
We can see in the hind-brain, we have the pons,
medulla oblongata, cerebellum.
These are all the more primitive parts of our brain.
The things that deal with our basic functionality.
We're talking about heart, lungs, talking about the basic
coordination for internal organs.
So that's your hind-brain, pons, medulla, cerebellum.
The mid-brain, well that's just the top of the brain stem.
Helps to coordinate movement, allow the visual and auditory,
so sight and sound, get's relaid through this location.
And the fore-brain.
Well fore is the front, so we're talking the front
of the cerebrum.
Part of the corpus callosum.
The thalamus.
All of these are more higher order or higher level thinking.
Helps to take information and coordinate it.
Thalamus.
Corpus callosum just connects the two sides, right and left.
So you can make sure your body's
doing the same thing each side.
The cerebrum, the entire top portion.
Decision making, conscious thought, language, comprehension.
It's really where the higher order thinking is occurring.
To give a little more detail, let's start in the hind-brain,
but look at the medulla oblongata.
The medulla oblongata is a very primitive structure.
It's very basic and simple in functionality.
It's at the most inferior or bottom portion of the brain.
It's what connects to the spinal cord.
It controls some vital functionality in your body.
You have your cardiovascular center.
Deals with heart rate.
Your respiratory center.
Deals with the amount of respiration.
How many breaths you take per minute.
And I don't know about you guys,
but heart, lungs, kind of important.
But what's scary, the medulla oblongata in humans
has the same basic functionality
as medulla oblongata in reptiles.
They still have a heart.
They still breathe.
So this is a very basic, primitive section of our brain
that controls our body's living ability.
We have some motor nerves crossing over here.
Now what's interesting is when they cross over,
that means that the right fore-brain
or the right part of your brain,
controls the left side of your body.
So when you're moving your left hand,
the thought process is on the right side of your brain.
While the left brain controls the right side of the body.
So you can say that your right hand is being controlled
by the left side of your brain.
So one of the things that my grandpa used to joke with,
because he was left-handed, he said he was in the
right frame of mind.
Because being left-handed is a dominant side.
That means his right brain was working more often.
So the joke was always he's in the right frame of mind,
right-handed.
Right fore-brain to left hand.
Well I'm right-handed, so my left fore-brain works more.
Does that mean that the other side of the brain
doesn't really work very much?
No. Sure.
Works plenty.
Both halves work.
The only difference is, which one controls
which half of the body.
All right.
The cerebellum.
We're still in the hind-brain.
This is how you coordinate some basic movement of your body.
Things like tying a shoe, walking,
swinging a baseball bat,
typing on a keyboard.
Once you perform an action, it can store the process
of muscle movement.
It can then replicate these sequences to complete them.
I mean look at a child trying to learn how to tie a shoe.
Well the first couple of times,
it's not going very well usually.
But the more they practice, the more they try,
the better and better it is.
I'm willing to bet, most people now
that are attending this class can probably tie a shoe
without looking at it.
The idea of you've done it so many hundreds of times
in your life, so simply go through and it's done.
It's stored in the cerebellum.
Pons.
Well the pons is just above the medulla oblongata.
It's connecting the higher parts of the brain
down to the medulla and spinal cord.
It's helping to regulate all the information
traveling through.
It also helps with some respiration control though.
So even though the medulla oblongata controls
a lot of respiration, the pons kicks in, it helps out also.
So let's move up a little bit.
Mid-brain.
Mid-brain is dealing with vision and hearing primarily.
Now when you hear something, does your head move
in reaction to it?
Sometimes.
Also when you're out and you hear a sharp snap
off to one side of you.
Good chance your head's gonna turn to that direction.
So the mid-brain is helping to control the movement
in response to what you hear or see.
For instance, if you're talking to someone
in a conversation, is it typical where you stare
completely away from them?
No, a lot of times you're probably looking at them
or at least near them.
Again, hearing and vision are coordinated through this area.
The eyes, pupil size, how much light is coming in.
A bright sunny day, those pupils are smaller.
An overcast, gloomy day, the pupils are larger,
letting more light in.
And up to the fore-brain.
This really is where our conscious thought is,
where are emotions are, where our higher order thinking is.
It will receive the information
from the mid-brain and the hind-brain,
but then it can integrate the information.
It can put it together.
It can form emotions based on the information given.
It can form thoughts based on the information given.
It can determine a cause and effect
based on the information given.
So we have the hypothalamus.
Well the hypothalamus deals with homeostasis.
Now I hope you remember, homeostasis is how your body
maintains proper levels.
Keeps everything balance and in the proper order.
The thalamus, think of it as "Grand Central Station."
Everything comes in.
All your sensory information comes in,
it's processed and then sent off, transferred out.
So what it's doing is taking all this information in
and figuring out where to send it.
What part of the brain to send this information to.
Limbic system and the cerebrum.
Now limbic system is kind of interwoven
throughout the cerebrum as well parts of the
thalamus and hypothalamus.
But what's important with the limbic system,
that really is your core, emotional center of your brain.
Your emotions all run through the limbic system.
But it's also what puts memory into short-term
or long-term storage.
The cerebrum, that's pretty much the entire
top portion of the brain,
language, decision-making, conscious thoughts,
perception of right and wrong.
List goes on.
These are all your higher order thinking skills.
So what's the structure of the cerebrum?
Well, we've got two halves.
We said right and left already.
They're in the right and left hemispheres.
They're held together by this corpus callosum.
The corpus callosum is just pure nerve tracks.
Its only job is allow information to go from right to left
or left to right.
And it's the only way information goes left to right
and right to left for the cerebrum.
Cerebral cortex.
It's gray matter along the outside of the cerebrum.
It's kind of helping with a lot of processing power.