BrainCraft

S3 E17 | FULL EPISODE

Wiggle Your Big Toe

Generally we move our bodies pretty automatically and quickly, thanks to myelin, insulation which coats some of our nerve cells. Though one autoimmune disease – Multiple Sclerosis (MS) – attacks this insulation, impacting patients’ motor and sensory functions. Researching brain development and the disease itself can help develop better treatments for MS patients in the future.

AIRED: April 06, 2017 | 0:02:52
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TRANSCRIPT

First things first: wiggle your big toe.

Go on!

It seems easy, but any time you move your big toe, you're sending a signal down the

longest neuron in your body.

You have a single cell, about three feet long, that stretches from the base of your spine

all the way to your big toe.

And it takes time for your biology to send a signal all that way.

In the wires in your home, electricity travels close to the speed of light:

In your body, your neurons have to move positively charged ions, which have mass and are harder

to work with.

But just like the wires in your home, your neurons can use insulation to send signals

faster.

Your body doesn't use plastic or rubber like this cord.

Instead, it uses a fatty coating called "myelin".

Without myelin, your slowest neurons would only be able to send signals at about 1 mph,

and the fastest would be about 22 mph.

Not only that, but a lot of the signal would get lost.

With myelin, the maximum speed is more than 12 times faster: 275 mph!

That makes it a lot easier to wiggle your toes.

Different neurons have different levels of myelination and signal speeds.

The neurons that tell your body what it's doing are some of the fastest, while the neurons

responsible for feeling pain and pressure are actually pretty slow.

But when myelin doesn't do what it's supposed to, meaning it doesn't insulate neurons

the way it should, you run into all sorts of issues.

Babies are born without most of their neurons myelinated, which is one reason why they have

no fine motor control, and can't really do anything for themselves.

As they grow older, their bodies and brains build myelin sheaths for their neurons, leading

to more coordinated, faster-thinking adults.

But what if you lose your myelin as an adult?

Medically, a loss of myelin is a demyelinating disease.

And the most common is MS, or Multiple Sclerosis.

MS it an autoimmune disorder: the immune system attacks the myelin of brain cells.

At first, this tends to affect balance and coordination, but can go on to impact other

motor, sensory, and cognitive function.

There's no clear cause or known cure... but studying brain development and the impact

of MS can help develop treatments and hopefully find cures for this and other autoimmune diseases

in the future.

In the meantime, if you're still sitting there wiggling your big toe... you can stop

now!

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