The Peripheral Auditory System
This presentation is the property of its rightful owner.
Sponsored Links
1 / 54

The Peripheral Auditory System PowerPoint PPT Presentation


  • 80 Views
  • Uploaded on
  • Presentation posted in: General

The Peripheral Auditory System. George Pollak Section of Neurobiology. 1. Hair cells, the transducers of the auditory system, and how they work. stereocillia of inner hair cells. stereocillia of outer hair cells. Organ of Corti. Basilar membrane. stereocilia on one hair cell. 9.

Download Presentation

The Peripheral Auditory System

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


The peripheral auditory system

The Peripheral Auditory System

George Pollak

Section of Neurobiology


The peripheral auditory system

1

  • Hair cells, the transducers of the auditory system, and how they work.

stereocillia of

inner hair cells

stereocillia of

outer hair cells

Organ of Corti

Basilar membrane


The peripheral auditory system

stereocilia on one hair cell


The peripheral auditory system

9


The peripheral auditory system

Potential difference between

Endolymphand cell interior

Potential difference between

Perilymph and cell interior

Kout

Kout

endolymph

= 0mV

= ~-70mV

Ek= 58 log

Ek= 58 log

Kin

Kin

Hi K+

Lo Na+

Hi K+

Lo Na+

Hi Na+

Lo K+

perilymph


The peripheral auditory system

-45 mV


The peripheral auditory system

Hi K+

low Na+

Hi K+

low Na+

Hi K+

low Na+

Hi Na+

low K+

Hi Na+

low K+


The peripheral auditory system

small leakage of

K+ into cell

No K+ into cell

K+ into cell

-45 mV

-70 mV


The peripheral auditory system

Next, we are going to

build a cochlea


The peripheral auditory system

Stapes

Basilar membrane


The peripheral auditory system

Sound is changed from

a pressure wave in the air

into mechanical movements

on the basilar membrane


The peripheral auditory system

round window


The peripheral auditory system

Traveling waves on basilar membrane

oval window

round window


The peripheral auditory system

The structure of the

basilar membrane causes it

to perform a

frequency to place transformation


The peripheral auditory system

Apex

responds maximally to low frequencies

flexible

wide and thin

Stiff

Narrow and thick

Base

responds maximally to high frequencies

Basilar Membrane

has continuously changing dimensions along its length


The peripheral auditory system

Basilar membrane converts frequency to a place of maximal response


The peripheral auditory system

Frequency-to-Place Transformation in the Cochlea


The peripheral auditory system

The motion on the

basilar membrane

causes shearing of the cilia on

hair cells and thereby causes

the hair cells to

depolarize and hyperpolarize in

response to sound


The peripheral auditory system

Organ of Corti

Basilar membrane


The peripheral auditory system

shearing of stereocillia

Organ of Corti

basilar membrane

basilar membrane


The peripheral auditory system

Why are there two types of

hair cells?


The peripheral auditory system

98% of the fibers that project into the central auditory system

are innervated by inner hair cells!!

98%


The peripheral auditory system

What are the outer hairs doing?

Answer: they act as amplifiers

of the mechanical motion of

the basilar membrane generated

by sound


The peripheral auditory system

release of transmitter

Hi K+

K+

-----

depolarization

hyperpolarization


The peripheral auditory system

Evoked mechanical responses of isolated cochlear outer hair cells.

_

+

_

+

_

+

Electromotility: OHC can change length in response to voltage change

Direct evidence of an active mechanical process in the organ of Corti

depolarized

hyperpolarized


The peripheral auditory system

Dancing hair cell

42


The peripheral auditory system

Outer hair cells are the only cells in the body that express prestin. Even inner hair cells do NOT have prestin.

+

+

+

+

+

+

+

+


The peripheral auditory system

Show movie of how Prestin works


The peripheral auditory system

Positive feedback loop

Basilar membrane motion

Sound stimuli

Hair bundle deflection

Change in length of hair cells

Membrane potential change

OHC

IHC

Sensory signal transmission


The peripheral auditory system

Normal response with cochlear amplifier

Apex

base

Basilar membrane

response without cochlear amplifier

Apex

base


The peripheral auditory system

How motion of basilar membrane

generates tuning curves in

auditory nerve fibers and thereby

imparts frequency selectivity

to auditory nerve fibers


The peripheral auditory system

5

50 dB SPL

6

7

8

10

11

9

Frequency ( kHz)

base

apex

6 kHz

60

7 kHz

50

40

Intensity (dB SPL)

8 kHz

30

20

9 kHz

10

10 kHz


The peripheral auditory system

30 dB SPL

5

best frequency

6

7

8

10

11

9

Frequency ( kHz)

Tuning Curve

The most basic feature

of an auditory neuron

base

apex

6 kHz

60

7 kHz

50

40

Intensity (dB SPL)

8 kHz

30

20

9 kHz

10

10 kHz


The peripheral auditory system

tuning curves in animals with no outer hair cells or

in animals without prestin gene

tuning curves in normal animals

high

Sound intensity

low

low

high

frequency


The peripheral auditory system

How is the tonotopic organization

that was first established on the

basilar membrane

preserved in in the

central auditory system?


The peripheral auditory system

Auditory cortex

Medial geniculate

Medial geniculate

Inferior

colliculus

Inferior

colliculus

Cochlear nucleus

Cochlear nucleus

Superior olive

Superior olive

Auditory nerve

Auditory nerve

Cochlea

Cochlea

Flow of Information Along the Central Auditory Pathway


The peripheral auditory system

superior olive

auditory cortex

medial geniculate

medial geniculate

Inferior colliculus

Inferior colliculus

cochlear nucleus

cochlear nucleus

Auditory cortex

Medial geniculate

Medial geniculate

Inferior

colliculus

Inferior

colliculus

Cochlear nucleus

Cochlear nucleus

Superior olive

Superior olive

Auditory nerve

Auditory nerve

Cochlea

Cochlea

The Frequency Representation on the Cochlea is Preserved in Every Nucleus of the Central Auditory System, and thus the Auditory System is Tonotopically Organized


The peripheral auditory system

Auditory cortex

Medial geniculate

Medial geniculate

Inferior

colliculus

Inferior

colliculus

Cochlear nucleus

Cochlear nucleus

Superior olive

Superior olive

Auditory nerve

Auditory nerve

Cochlea

Cochlea

The Frequency Representation on the Cochlea is Preserved in Every Nucleus of the Central Auditory System, and thus the Auditory System is Tonotopically Organized


The peripheral auditory system

The Frequency Representation on the Cochlea is Preserved in Every Nucleus of the Central Auditory System, and thus the Auditory System is Tonotopically Organized


  • Login