Myelin

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来自 The University of Chicago 的课程

了解大脑：日常生活中的神经生物学

652 个评分

The University of Chicago

了解大脑：日常生活中的神经生物学

652 个评分

Learn how the nervous system produces behavior, how we use our brain every day, and how neuroscience can explain the common problems afflicting people today. We will study functional human neuroanatomy and neuronal communication, and then use this information to understand how we perceive the outside world, move our bodies voluntarily, stay alive, and play well with others.

从本节课中

The Nervous System

Neurobiology is a rapidly growing area of scientific research, and is becoming increasingly prevalent in the news and popular culture. In this course, we will study of the nervous system from a biological perspective by exploring the fundamental concepts in neurobiology, including how we sense the world, how we act in the world, and common neurological disorders.

Meet the Stars: Neurons2:20

Parts of the Neuron3:57

Neuronal Uniqueness: Stars of the Sky8:58

Glial Cells6:47

Demyelinating Diseases3:05

与讲师见面

Peggy Mason
Professor
Neurobiology

[MUSIC]

Okay, so we're going to talk about myelin now.

Myelin is a, is a fatty wrap that goes around some axons.

Now, what's the difference between a myelinated axon and a naked axon?

A naked axon is one that doesn't have mylelin, so it's unmylinated.

so, an unmylinated, or naked axon, can only, transfer information at a slow rate.

So the rate that it's transfers information is 0.2 to 1 meters per second.

That means to go 1 and a half

meters, which is roughly the distance between [COUGH]

my toe, and right here.

To go that distance would take me seconds.

At least, a second and a half.

And probably more like 5 seconds.

[BLANK_AUDIO]

Now, once we put on myelin, information transfers much much faster.

It can go between 2 and 120 meters per second.

If it goes at 120 meters per second, the whole game is over.

Information is gone from here to here in 12 milliseconds.

.012 seconds.

So very short time, in perceptible to us.

And that is a, obviously a very useful thing, so

that we can get information in time to actually use it.

So, the information that we need the,

the fastest is information about keeping our balance.

And so, as we walk along, if we bump

into something and we stumble, we need that information fast.

If we had to wait for a second or two, we'd be on the ground.

All the neurons that support our posture

against gravity, those neurons transfer information really fast.

Alright, so let's talk a little bit

more about the information that gets transferred.

That information occurs in, it's a 0 or a 1.

[BLANK_AUDIO]

There's either an a point of information or not.

And so it's very much like a computer

code, where what we're seeing is a series of

of 0s or 1s and what's important,

the 0s are less important but the temporal pattern of these ones is very important.

So, we want to know, at every millisecond, is there a 1 or is there a 0?

If there's a 1 we want to know the temporal pattern of those ones.

That's the neural code.

And these ones are actually, I, I'm going to give you the name for that.

That's an action potential,

[BLANK_AUDIO]

also called a spike.

And we talk about firing spikes, neurons fire spikes.

So, the timing of these spikes is what carries information.

The spikes are going to travel down this axon, so lets now imagine

in this situation that blue here is supposed to be the miling.

These are wraps and their wraps that go around the axon.

I, I've, I've drawn it as a cut away, but the wrap will go all the way around here.

And the information, the spikes actually jump.

That's what makes it so fast.

They don't have to they don't have to, actually be

carried through the places with the Myelin, they can actually jump.

And so things, anthra, the spike information

is transferred very quickly, down this axon.

Now, if we lose this myelin, if we lose this myelin, just

a little bit of myelin here, now, this is going to creep along.

And it actually, it's either going to be really slowed or it may fail altogether.

So, this if our original message is this.

[SOUND].

And now, we have a demyelinating disease, what

we're going to end up with is something that's

spread out, because it's slower.

And every once in a while, it's going to miss bits.

And now, the neuron that we're talking to is getting a very incoherent message.

This is very different from this and that is the problem with demyelination.

By, because an [UNKNOWN] because axons are

demyelinated, the information transfer is very degraded.

It's a garbled message and that's a problem.

And so in the next segment what we're going to look at is the two different

major types of demyelinating diseases.

[MUSIC]

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