Otoacoustic Emissions

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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

774 ratings

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.

From the lesson

Hearing

The sound of birds chirping in the morning, a babbling brook or crashing waves on the beach, or warm conversation with the ones you love. The experience of all these things requires the ability to hear. Arguably the most important sense for human communication, it is also the most commonly impaired of our senses. In this module, you will learn how the human ear is artfully designed to enhance our ability to hear the human voice. You will follow sound waves as they travel from the external world, to the eardrum, through the bones of the middle ear, and to the cochlea that transduces sound information into neural impulses.

Cochlear Amplifier3:21

Outer Hair Cell Motility6:12

Otoacoustic Emissions3:25

Hearing Loss7:08

Weber and Rinne7:33

Meet the Instructors

Peggy Mason
Professor
Neurobiology

[MUSIC]

Okay, so what we're going to do now is we're going to imagine what

would happen if we reversed hearing.

So what we've talked about so far is sound coming into the cochlea, and

sound coming in and making a wave that affects hair cells in the cochlear dot.

Let's just imagine for a moment that we,

we start with the activation of these hair cells.

Okay? So we're just going to zap them.

They're going to be activated, and in particular,

we're going to start by activating outer hair cells.

The outer hair cells, the cochlear amplifier, that's going to,

they're going to move, right?

So they're going to move because they're activated.

And now, that's going to move up and down this membrane,

which is going to produce a wave that goes backwards.

Well, once this goes backwards, it's going to go right back

through the middle ear, through the ossicles, it's going to move them up and

down, and it's going to end up moving the tympanic membrane back and forth.

And as a result, we're going to have a small intense,

a low intensity sound wave come out from the ear.

Now that's pretty amazing.

I mean, you can't hear that, but if, if, if a physician puts a microphone

into the ear canal, they can pick up that sound, and

that is called otoacoustic emissions.

So sounds that come back out of the ear are otoacoustic emissions.

Now what, how could we do this without zapping outer,

magically zapping outer hair cells?

Well, as it turns out, when sounds come into the ear,

they actually move these outer hair cells.

So in, so essentially, we can activate these our hair cells with sound,

and then we're going to get this bounce back of otoacoustic emissions.

And what that o, what that bounce back tells you is that everything

from here on out is, is healthy.

It's working.

So this is a really use, useful diagnostic tool.

Physicians use this to try and understand whether for

instance, babies can hear or not.

It's not something that you want to do yourself, but physicians can test for

otoacoustic emissions in babies and

in other nonverbal individuals.

And the other really cool thing about it is that otoacoustic emissions just really

tells you how powerful the cochlear amplifier is.

And we're going to see another side of the power of the cochlear

amplifier in the final segment of this module where we're going to talk about

the typical types of hearing loss.

[MUSIC]

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