Practice English Speaking&Listening with: Integrative Biology 131 - Lecture 24: Development of...

MARIAN DIAMOND: Let's start this morning

with our classification of neurons.

We have a structural classification, a functional

classification, and a chemical classification.

You can use any of them when you're talking about neurons.

So let's begin with our structural classification.

We could have unipolar cells, and these you'll

find primarily in the embryo.

We'll have just a soma and a process.

Then we can have the pseudo unipolar, which you've already

had, but we'll put it in for completion's sake.

Pseudo unipolar.

And it will be found in the dorsal root ganglia.

You'll see later that that's your spinal ganglia.

The dorsal root ganglion.

And that, as we showed previously,

you'll have two processes, but one's stem to the cell,

to the soma, so we come up with a single cell.

We had a peripheral process.

Why don't we just call it a dendrite,

because it's myelinated.

So this is a rare exception, this peripheral process

is myelinated, though it serves the function of a dendrite

by bringing the information into the soma.

And we call a process that's on its way

to the CNS a central process.

Then we have bipolar cells.

Bipolar, which just tells you then we're

going to have two processes.

A single soma.

So here, we'll have a dendrite and an axon

taking the impulse away.

Taking the impulse in.

Where do we find bipolar cells?

We'll find them in the retina, in your eye.

Guess Eye receptor, your retina.

We've already had one group of them.

We had them in the olfactory epithelium.

So a bipolar cell in the olfactory, the olfactory nerve.

And we'll find them in the auditory ganglion.

Auditory ganglion.

And then, by far, the most of the nerve cells

will be multipolar So multipolar is the most numerous.

So you only have, really, two in the adult

to worry about, bipolar, pseudo unipolar,

and then everything else is multipolar.

Example, we'll give the anterior horn cell again.

It's got its many poles.

Anterior horn cell.

We'll use all of these as we're developing the functional

aspects of the nervous system.

So we're just gathering up our building blocks.

Now then, we have our functional classification, again

very simplistic, but basic to get us started.

We'll have motor.

We'll have sensory.

And what's the third?

Interneuron, yes.

The interneuron.

So example of a motor cell, we'll keep using it

because I hope 10 years from now, you'll remember,

the anterior horn cell.

It's a motor cell.

It's what's allowing me to write on the blackboard.

The anterior horn cell.

Then the spinal cord.

Sensory, example of sensory.

Once again, I'll use the same one.

Your dorsal root ganglion.

Everything coming into your spinal cord

passes through the dorsal root ganglion.

These are also called spinal ganglia, collectively.

And then we have the interneuron.

So most neurons are interneurons.

They will connect the motor and the sensory.

So let's just say they're between motor and sensory.

Sensory will be bringing things into the CNS,

and then it goes over to interneurons

until you want a function, and then

the motor will take it out and carry out the function.

So then we have chemical classification.

And there are so many chemicals associated

with the nervous system now, we can't

begin to take a couple of hours to give them to you.

So we'll just give you three examples.

We have what are called cholinergic neurons.

This will be chemical.

Cholinergic neurons.

So those who've had this before, what's the transmitter?

STUDENT: Acetylcholine.

MARIAN DIAMOND: Acetylcholine, right.

Acetylcholine.

We have adrenergic neurons.

What's the transmitter?

STUDENT: Adrenaline.

MARIAN DIAMOND: Adrenaline, yes.

Then let's just put in one more.

Let's put in a GABAergic.

GABAergic.

What's the neurotransmitter?

STUDENT: GABA.

MARIAN DIAMOND: GABA.

What's it stand for?

Gamma amino.

What's the next word?

STUDENT: Butyric.

MARIAN DIAMOND: Butyric.

Last word?

STUDENT: Acid.

MARIAN DIAMOND: Acid.

So that gives you examples.

As we said, there are many, many more of these now.

So just a few more basic terms.

We've been using them, but we haven't defined them.

What we call groups of neurons.

So groups of neurons of like function inside the CNS

are called what?

STUDENT: Nuclei.

MARIAN DIAMOND: Nuclei.

Plural.

A nucleus, singular.

Or nuclei, plural.

So example, since we've talked about it before,

we've talked about the vagus nerve.

When we go to see where it's originating from, part of it's

originating from the dorsal motor nucleus of 10.

Dorsal motor nucleus of the 10th cranial nerve.

And what's the name of the 10th cranial nerve?

The vagus, right.

So we review and review, right?

Constantly get it from different perspectives.

Now a group of nerve cell bodies outside the CNS--

group Of nerve cell bodies outside the CNS,

what do we call them?

STUDENT: The ganglia.

MARIAN DIAMOND: Ganglia.

Ganglion, singular, and ganglia, plural.

So with this very simplistic introduction,

we have some tools to begin to work with.

Let's go now to the development of the nervous system.

I give the development because it will give you

the terminology, basically, for the whole nervous system

at the beginning so that we can use it

for more advanced functions.

So let's look at the development of the nervous system.

And we all started with a simple neural tube,

with our nervous system starts as a simple tube.

This is called the neural tube, and it

will have a central canal.

That's our central canal.

This is the head end, tail end.

This end is going to form your brain.

So what's the rest of all of this going to form?

STUDENT: Spinal cord.

MARIAN DIAMOND: The spinal cord, sure.

Your whole CNS.

So the neural tube develops the CNS.

Now, let's take a section through this cranial end,

a cross-section of neural tube.

And our central canal is changing.

Not just a simple elongated tube.

It's taking on some shape here.

This now is our central canal.

And the central canal in the head end

will form the ventricles of the brain.

Form ventricles of brain.

So you have these chambers inside the brain coming

from the original central canal.

We have a landmark here, the so-called sulcus limitans,

because we can use it for functional considerations.

So we'll put our landmark here.

Use lateral projections of the central canal,

we call them the sulcus limitans.

Sulcus limitans.

Limiting sulcus.

Then we can draw an arbitrary line

across to the periphery of our tube,

and everything dorsal to our line

will go into what's called the alar plate.

Alar plate.

The alar plate is sensory.

Ventral to our arbitrary line, we'll have the basal plate.

So what's everything in the basal plate?

STUDENT: Motor.

MARIAN DIAMOND: Motor.

What do they call the gene that stimulates this arrangement?

STUDENT: Hodgkin's [INAUDIBLE]?

MARIAN DIAMOND: No.

Sonic hedgehog.

I didn't name it.

It's the gene that affects the protein that

affects the alar and basal sensory and motor plates.

So we're always learning things new.

It's never always the same.

So now, with this, we want to introduce a few more

terms here.

We need to have a roof plate.

And as you would anticipate, the roof plate

is going to be up here.

So this gives us just some basic divisions

that we'll work with as we go along

if we take a section through the area of the brain.

This will be, essentially, the same in the spinal cord

initially, and then the brain takes off and becomes so

much more elaborate.

So now, let's look at the divisions of our neural tube.

As I've said before, the liver only weighs seven pounds--

seven pounds.

The liver weighs three pounds, and the brain

weighs three pounds.

And yet, the liver, every single cell

is the same as every other cell.

So if I take some of my liver here, or liver here,

or liver here, or liver here, they all look the same.

They're phenomenal factories.

But the brain only weighs three pounds.

If I take some here, it'll look entirely

different from some here or some here.

Everything's different.

That's the beauty of it.

That's the contrast.

That's the challenge.

So now, let's look at our divisions of the neural tube.

We'll start very simple again.

Three main divisions and down to our cord.

Use simple terms to start with.

Forebrain, midbrain, and hindbrain.

Now we change the terminology, put it into our old languages,

because the literature does that,

so that you're familiar with what they are.

I had lots of fun in an office hour the other day [INAUDIBLE]

on things on the web and working it out and explaining

all the terminology.

Because students are beginning to get it.

Now they can begin to talk about it.

So it's our forebrain, it's the prosencephalon.

So encephalon means brain.

Pros means before.

So this is our forebrain.

Then we have the mesencephalon.

Mesencephalon, which is our midbrain.

Heard of encephalitis, haven't you?

Encephalitis, inflammation of the brain.

And the hindbrain will now be the rhombencephalon.

And the "rhomb" just deals with the shape, a rhombus.

So it's the shape of a rhombus in Greek.

We'll see when we look at the ventricle how it changes.

Now then, these continue to divide and give us

more divisions.

And then we'll look at the derivatives

of each of these divisions.

The prosencephalon is going to change into the telencephalon

and the diencephalon.

And the diencephalon.

It's worth the investment of time to get familiar with these

to begin with.

Then you can handle things from now on anywhere in the brain.

The mesencephalon stays the same.

The rhombencephalon divides in two,

just as did the prosencephalon.

So we have the metencephalon, metencephalon and the,

which is the last one?

Do you know?

Myelencephalon.

Myelencephalon.

How do I remember their order?

Alphabetically.

S, T, and Y. So you can think this is head end, tail end,

so S, T, E, just as it is in the alphabet.

So it'll help you.

Because encephalon is common to all.

So now what we're going to do is take each one

and say a few words about it so you get your orientation

of the total brain.

Because we'll be bringing things in to part of it,

then take it on to another part, to another part,

modifying the impulses.

So we need the basics, basics, basics first.

Let's start now with our myelencephalon.

What are the derivatives of the myelencephalon.

Simple, because it's a very basic part of your brain,

just adjacent to the spinal cord.

I mean, this brain elaborates.

For early animals, just had a spinal cord.

Information coming in, going out, sort of reflex.

Then they add some more cells to modify that.

So you put in a myelencephalon.

And then we go on, and we're going

to see the cerebral cortex is going to be way up here,

the highest, to modify everything.

So our myelencephalon, the structure we're going to form

will be the medulla.

I'll give you the full name just so you've heard it.

Medulla oblong-- as soon as I spell it right--

oblongata.

There we go.

We seldom use that.

But the kidneys have a medulla.

The adrenals have a medulla.

When people talk about the medulla,

they have to say of the brain, which structure they're

dealing with.

Your medulla is only one inch long.

So it's a very small part of your total brain, when

you picture it, just one inch.

It's one inch in a chimpanzee, too.

So it hasn't evolved that far up to the human.

So it has lots of functions in that one inch, very dynamic.

As we said before, it's essential to life,

but deals primarily--

it's got a center for cardiovascular and respiratory

functions.

Where did I say the phrenic nerve gets its control

for its rhythmic firing?

Pons and medulla.

This will be going down for your phrenic nerve,

to keep you breathing.

Part of respiration center.

So there are lots of cranial nerves that--

all of a sudden, I lost it.

No, it's there.

The cranial nerves associated with the medulla

will be eight through 12.

The name of the ventricle in the medulla

will be the fourth ventricle.

You have four ventricles.

We're starting at the bottom.

This is going to have the fourth ventricle.

As soon as you start reading your MRI scans,

you'll be alluding to these all the time because they're

major landmarks.

So how does-- let me just do this.

How does your neural tube change as it forms the medulla?

You could say-- just put your two hands together.

The palms represent the basal and the fingers the alar.

Here's my sulcus limitans in between.

When I come to the medulla, it opens out like this.

So out here will be my alar.

My basal will still be my pons.

But what is important is what happened to that roof plate.

We extended it tremendously.

So if we do this--

oh, our roof plate, I guess, was pink, wasn't it?

So I-- So that's our roof plate.

So this is now alar plate, basal plate, basal plate, alar plate,

and this is our roof plate.

When you study neuro in detail, you'll

see how important this is.

And this is our fourth ventricle.

So look at how it has changed.

I've seen people fail a PhD exam for not being able to work out

what nuclei are in various areas because they

didn't have their fundamental development

of this area of the brain.

So this will give us a very fundamental picture

of our medulla.

Let's move on up to the metencephalon.

Two major derivatives from the metencephalon.

Who knows those?

STUDENT: Cerebellum and [INAUDIBLE]..

MARIAN DIAMOND: Pardon?

STUDENT: [INAUDIBLE]

MARIAN DIAMOND: Yes.

What are we coming up from?

The cerebellum and?

STUDENT: Pons.

MARIAN DIAMOND: Pons, right.

Derivatives will be the cerebellum and the pons.

The cerebellum will be on the dorsal side,

the pons on the ventral side.

So briefly, what are these.

Here's our medulla down here.

Our spinal cord.

And we've put in our cerebellum.

And on the ventral side, we'll have the pons.

So now what in the world are those?

The pons is a bridge.

That's what pons means.

We'll just expand it.

Here's our pons.

Here's our cerebellum.

What's it bridging?

It's a bridge of fibers connecting the cerebral cortex,

which is up here, the most highly

developed part of your brain.

From cerebral cortex down to cerebellar cortex.

So I'll have pyramidal cells way up here

in my cerebral cortex that will have axons

that are going to go all the way down, down, down,

down to my pons.

Masses of fibers coming down.

And then they will synapse and send fibers

into the cerebellar cortex.

So major tracks for the cerebral cortex

to talk to the cerebellar cortex.

From cerebral cortex pyramidal cells to cerebellar cortex.

And the connecting link is the pons.

So that essentially gives you pontine function.

Tremendous amount of fibers coming in.

People are still trying to learn why--

actually, this whole cortex should have fibers going in.

What then is our cerebellum doing for us?

Cerebellar functions.

We learn this early.

We'd have learned it, too, balance and coordination.

And now, as we're beginning to understand the connections

with the cerebral cortex, it plays a role

in learning, fine movements.

I'll give an example of a pianist.

See those hands.

Without a cerebellum, that wouldn't be possible.

So with a pianist, the cerebellum

is affecting both hands and feet.

You've got those pedals going as well.

Right?

Terribly important.

We've tested what it means before.

So that gives us just a basic introduction

to our metencephalon.

Let's move on to the mesencephalon.

I'll move it over here.

We need to take the mesencephalon-- maybe

if I give it some dynamics for you.

The bullet that shot President Kennedy

was lodged in his mesencephalon, where they couldn't go in

for it, because you'll see how it's not on the surface.

It wasn't anyplace they could go for.

It was deep.

So the mesencephalon-- well, first,

let's look on a dorsal view.

So you know part of the--

you have to have all these views.

We'll look at-- you'll see these four rounded structures looking

down.

I'll show pictures of these so you'll see them.

Let's just get the basic arrangement now.

I think I'll take this off.

Since there are four of them, they're

called the quadrigeminal bodies.

Quadrigeminal, four bodies.

Quadrigeminal Sham bodies.

And the two superior ones are called the what?

Superior colliculi.

Superior.

Colliculi is just little hill, because they

look like little bumps here.

Superior colliculi.

What do they do for you?

Visual motion.

Pick up that little fly out there.

You hit your tennis ball; you're watching it.

Visual motion.

The two inferior ones, what are you going to call them?

STUDENT: Inferior colliculi.

MARIAN DIAMOND: Inferior colliculi.

Sure, you can begin to name some things that make sense, right?

Inferior colliculi.

They're part of your auditory pathway.

You hear a loud bang, and you jump.

An auditory reflex response through

your inferior colliculi.

Very simplistic here.

Any one of these, you could spend hours talking about.

All right.

Let's take now a--

what kind of section do I want?

Let's take a ventral view.

Ventral view.

And here, we'll have our diencephalon up here.

We'll see these fiber tracks coming down like this.

From down here, we have fibers going in this direction,

and they're going out to a structure that looks like this.

So we've just left our metencephalon,

and we developed these two structures.

So what are they?

These two structures, we just developed in our metencephalon.

STUDENT: [INAUDIBLE]

MARIAN DIAMOND: Pardon?

STUDENT: [INAUDIBLE]

MARIAN DIAMOND: Pons and cerebellum, sure.

This is pons and cerebellum from a ventral view.

Pons and cerebellum.

Just letting you know where we are, because we've--

this was all metencephalon.

Now these fibers, here, by the ventral surface

of our mesencephalon, so these are called cerebral peduncles.

It'll come together.

It just takes time.

You're getting the parts.

We'll show how they're connected.

And now we're going to take a coronal section

of the mesencephalon.

And we'll see the colliculi this way.

We'll take it on down this way.

And our central canal has changed completely.

STUDENT: Professor?

MARIAN DIAMOND: I'm sorry.

STUDENT: What is D1 on the ventral view?

MARIAN DIAMOND: Oh, I'm sorry.

Diencephalon.

That was just abbreviation for diencephalon.

Please ask.

All right.

Now, this is our central canal.

What do we call the central canal in the mesencephalon?

STUDENT: [INAUDIBLE]

MARIAN DIAMOND: No.

That will be between the diencephalon.

This is between the fourth and the third.

Pardon?

STUDENT: Cerebral aqueduct.

MARIAN DIAMOND: Cerebral aqueduct.

Good for you.

This is the cerebral aqueduct.

And this is where the central canal is smallest in the brain.

So you get a tumor in the midbrain,

and you can block your cerebral aqueduct,

and you block all the flow of CSF, cerebral spinal fluid,

that's in your ventricles.

So it's a crucial part.

We have a professor who blocked it.

He'd come to class to show us.

They put a shunt in to let the CSF run,

and they ran it under his skin and took it down,

and it went into his abdominal cavity.

The kids would just come touch it.

They loved to touch his head, but he was--

I mean, he'd sort of retired, and everybody

had forgotten him.

But once he got that shunt, he became a star in class.

So that was nice.

All right.

But it tells you how important each one of these things

is, if one stops, to tell you the dynamics of them.

And there we are.

And we didn't get very far, did we?

We have lots to go.

But I think what I will do while I have this,

just to make this dynamic for you,

here are your cerebral peduncles in this view.

They're down here.

This is coronal; this is ventral.

This is ventral.

This was a ventral view.

But you took them across this way, so they looked this way.

What are these, then?

Generic term for them, because we

don't know what level we are?

Corpora quadrigemina, right?

You're on the dorsal surface.

So these are your corpora quadrigemina.

And we're going to put in here--

we'll go to my slides--

a very important structure here.

We know more about its function than just

about any place in the brain.

What's it called?

Substantia nigra.

The black substance.

We'll come back to that next time.

But let's have our slides.

Substantia nigra.

If you see me sitting here doing this,

it means I'm losing cells in my substantia nigra.

Parkinson's disease.

We'll pick that up next time.

Let's review.

All right, here's our main character, all fully formed,

just so you can see what we're developing.

We take it through development, so you get the stages.

Here's our one-inch medulla.

There's our cerebellum.

Our pons is going to be tucked in here.

We haven't developed our cerebral hemispheres,

but we'll come to them.

Next one.

This gives you a chance to introspect.

How many times have you introspected

into your own body?

When you brush your teeth tonight, open your mouth,

look back, you'll see are your uvula.

Then you'll have your vertebral column.

And then imagine you could go straight through,

and you'd be at your spinal cord.

But then start to climb.

This is medulla.

This is cerebellum.

This is pons.

This is fourth ventricle.

Here are colliculi, superior, inferior.

Here's our cerebral peduncle.

We only got that far.

We have all this yet to develop.

Next one.

This just shows our tube for our prosencephalon,

mesencephalon, rhombencephalon.

And we're going to see a change so that the prosencephalon is

going to form our cerebral hemispheres.

Here's our diencephalon here.

The eyes will come out from there, the retina.

Then this is our future aqueduct.

It's big still.

Here's our fourth ventricle.

And we could see how it's beginning to curve and change.

And the next one.

And this shows what it's--

this is hindbrain, midbrain, forebrain.

What happens if this does not close one month in the embryo?

You don't form a brain.

You have what's called anencephaly, without a brain.

We've seen those when I take my small class over to UCSF

to pathology, where the brain--

this did not close, obviously.

Yours closed one month in utero.

So we go over here.

Here's our medulla.

Here's our pons.

The cerebellum's going to develop here.

Here's midbrain.

If you got this far, here's our medulla.

Here's our pons.

Here's our cerebellum.

Here are the colliculi.

Then here are the cerebral peduncles.

Pede Next one.

And this is just putting it in the head

so you could see cerebrum is going

to come from the telencephalon.

The diencephalon here.

The midbrain.

The cerebellum.

And beginning to develop, the cerebellum, pons, medulla.

Already, you're getting tired of hearing them.

There's superior colliculus, inferior colliculus.

And there are your peduncles on the ventral surface.

This was dorsal surface.

Next one.

And this is to show the brain of an embryo at four months.

You see none of the fissures.

People say, well, when does it begin to fold?

Well, you could say at least you know you don't

have folds at four months.

So roughly around five months in utero do you begin to fold,

because if you didn't fold, you'd

have a brain that's 2 and 1/2 feet square.

So it's got to fit in this skull to get through this birth

canal, so it folds.

But see, this just shows, pons, cerebellum, medulla.

Midbrain's in here.

Next one.

Now we're looking at a dorsal view.

Here's why it's called a rhombencephalon.

This looks like a rhomboid figure.

This is the roof of the fourth ventricle.

Medulla's down here.

We've taken off the cerebellum so we

can look down and see superior colliculi, inferior colliculi.

We're going to go up into thalamus, basal ganglia,

and the hemispheres.

And the next one.

And this shows the pons from a ventral view.

Here's the pons.

You can see it's a real bridge going into the cerebellum,

but it's connecting all the areas of the cerebral cortex,

sending them all in, because we know now

that the cerebellum deals with learning.

We used to think it was all of these muscle things.

It's very definitely involved in our learning.

Here's your medulla.

And if we went deep in here, we'd go on to our diencephalon.

Next time.

But this is mesencephalon.

Next one.

And this just shows the fibers coming

from the cerebral cortex.

They've got to all come in, funnel down.

When they pass through here, this

would be your cerebral peduncles coming in.

These fiber tracks have to go clear down to my spinal cord

so I can be playing with this pointer.

And the next one.

Next one, please.

This one just shows the development

of an area, the insulo.

It's-- why some people will be speaking in 131A.

It's in a very important area for our speech.

And the next one.

Is that it?

STUDENT: [INAUDIBLE]

MARIAN DIAMOND: That's it.

Enjoy.