Otoconial Disorders

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Understanding the Brain: The Neurobiology of Everyday Life

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The University of Chicago

Understanding the Brain: The Neurobiology of Everyday Life

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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.

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The Vestibular Sense & Gaze

The vestibular system and gaze control give us so much but are grossly under appreciated. They are so fundamental that we discount them, assuming that they will always be there. When the vestibular system fails us, its importance dominates our lives. Living with either a vestibular or an eye movement disorder is very disruptive to everyday life. In this module, you will learn how the inner ear is designed to detect and respond to head movements. You will learn about the circuit that connects the inner ear to the motoneurons that control the location of your eyes, allowing us to reflexively maintain our view of an object even as we move about in the world. Finally, we will talk about how you can modify this reflexive control of the eyes and how you can control where you are looking.

Hair Cell Orientation6:00

Yoked End Organs, Part 15:27

Yoked End Organs, Part 23:47

Otoconial Disorders5:54

Visual Integration3:44

Познакомьтесь с преподавателями

Peggy Mason
Professor
Neurobiology

[MUSIC]

Okay, so let's talk about a couple of common problems that can go,

go on with the otoconial masses.

Remember that the hair cells are here, the otoconial mass is here.

The otoconial mass is made of very special proteins,

otoconins that are made during fetal life.

They're made before you're born and

whatever you made before you got born, that's all you got.

There's no more making new ones, we don't regenerate the otoconians,

we don't regenerate the otoconial mass.

There is goo that, that keeps these keeps the otoconeians together,

and keeps this as a mass.

But as we age some of the goo comes off,

and you might get a little chunk of this bit that comes off.

And another, another reason why a chunk of this would come off is

this has happened to several of my graduate students

where they go on very, robust shall we say roller coasters and,

a little chunk of the otoconial mass came off.

Now, what would happen if a piece of the otoconial mass came off.

Let's look at a, a side view of the canals.

So, the otoconial mass is, is right here.

There, the, both the horizontally and

vertically oriented ones are about right there.

And this is all continuous.

So, what's the lowest point in this whole vestibular apparatus?

It's this.

And so what happens, is that a, the piece of the chunk,

comes down here, and can tickle, these hair cells.

And it's,

it's stimulating those hair cells only when you're in a certain position.

But the moment it, it, it stimulates them, you have a,

a, perception of your head accelerating.

Your head is accelerating, but

your vista, your visual information tells you that's not so.

You get a sense of vertigo and it's paroxysmal.

The moment tho, that little bit of otoconial mass tickles the hair cells

you get a paroxysm of vertigo and it's dependent

on the position and that's called Benign Paroxysmal Positional Vertigo or BPPV.

It is an extremely common condition.

Luckily, it can be reversed.

In many cases it gets reversed by actually doing a,

a maneuver that, that essentially does this and what you're trying

to do is you're trying to throw the little bit of otoconial mass up.

And back into the vestibulum.

You're trying to throw it back out of the posterior, out of this most,

lowest point of the posterior canal, and back into

the into the vestibulum the center part of this vestibulum,

where presumably, at some point, it can get reabsorbed.

Okay.

So that is is a common problem.

Luckily you can reverse it in, in almost all cases.

The second problem is that, as I said before,

as we age this goo gets less gooish.

And the otoconial mass kind of, disintegrates.

It loses mass.

If we go back to our, our, you know,

which, what do we want to sense gravity with, a stone or a feather?

Well, a feather is not a good way to sense gravity.

And as that string is not taut because it's not heavy enough.

So as we age this, this otoconial mass can get so

light that it's actually a very poor sensor of gravity.

And in that situation, you have essentially old-person equilibrium.

So just like we have presbycusis age-related hearing loss,

presbyopia, age-related stiffening of the,

of the lens and, and therefore lack of near accommodation.

We also get something that I will call presbyequilibrium.

This is not a term that has taken the, the field by storm but

the point is that as we age, there's an a very

common decrease in the mass of the otoconial masses and

therefore a decrease in our ability to sense gravity.

I know that a older friend of mine once told me that

as he stepped off a curb, he just hoped for the best.

There is in older people, there really is a compromise of the ability to know

which way is up, and, and and to keep balance.

Okay.

So, in the final segment of this module,

we're going to look at a very slow head movement.

[MUSIC]

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