Physiology Of Hearing Animation👂Understanding the Sound Journey 🎶

Summary

This video provides a detailed overview of the physiology of hearing, explaining the anatomy of the ear, which is divided into three regions: the outer, middle, and inner ear. It highlights the functions of each part, especially the cochlea, which converts sound waves into neural signals. The video discusses the roles of hair cells in sound amplification and frequency detection, and introduces the traveling wave theory of Von Békésy, which explains how different frequencies are processed within the cochlea. It concludes by emphasizing the importance of outer and inner hair cells in hearing.

Takeaways

• 🦻 The ear is divided into three regions: the outer ear, middle ear, and inner ear, each with distinct functions for hearing and balance.
• 👂 The outer ear, which includes the pinna and external auditory canal, collects and amplifies sound waves.
• 🎧 The middle ear contains three small bones (malleus, incus, and stapes) that amplify sound waves and transmit them to the inner ear.
• 🌀 The inner ear houses the cochlea, vestibule, and semicircular canals, which are involved in hearing and balance.
• 🎶 The cochlea, a 35 mm long spiral organ, converts sound waves into neural signals through vibrations of the basilar membrane.
• 🎵 Different frequencies of sound cause specific parts of the basilar membrane to vibrate, allowing the cochlea to analyze sound frequencies.
• 💡 Hair cells in the organ of Corti are responsible for converting sound vibrations into electrical impulses that are sent to the brain.
• 🎤 Outer hair cells in the cochlea amplify sound waves, enhancing sensitivity to various frequencies.
• ⚡ Inner hair cells are the primary transmitters of sensory information, while outer hair cells amplify the signal.
• 🧠 The auditory nerve fibers transmit electrical signals from the cochlea to the brain, where sound is processed and interpreted.

Q & A

What are the three functionally distinct regions of the ear?

The three functionally distinct regions of the ear are the external (outer) ear, the middle ear, and the internal (inner) ear.

What is the main function of the outer ear?

The main function of the outer ear is to collect sound waves through the pinna and direct them into the external auditory canal, which helps amplify the sound.

How do the ossicles in the middle ear contribute to hearing?

The ossicles (malleus, incus, and stapes) in the middle ear amplify sound waves and transmit them from the eardrum to the inner ear.

What is the function of the cochlea in the inner ear?

The cochlea is responsible for converting sound waves into neural signals that are transmitted to the brain and interpreted as sound.

How does the basilar membrane contribute to hearing?

The basilar membrane vibrates in response to sound waves in the cochlea, causing hair cells to bend and release neurotransmitters, which generate electrical impulses sent to the brain.

What is the role of the outer hair cells in the cochlea?

The outer hair cells in the cochlea amplify vibrations of the basilar membrane, enhancing the sensitivity and selectivity of the cochlea to different sound frequencies.

How do the inner hair cells differ from the outer hair cells in terms of function?

The inner hair cells are primarily responsible for transmitting sensory input to the auditory nerve fibers, whereas the outer hair cells amplify sound signals before they are transmitted.

What is the role of tip links in hair cells?

Tip links are elastic structures that connect stereocilia on hair cells, allowing mechanically sensitive cation channels to open when stretched, leading to ion flow into the cell and signal transmission.

How does the basilar membrane analyze different sound frequencies?

The basilar membrane is stiffer at the base and more flexible at the apex, allowing it to respond to different sound frequencies—high frequencies peak near the base, while low frequencies peak near the apex.

What is the traveling wave theory of Von Békésy?

According to the traveling wave theory of Von Békésy, sound waves entering the cochlea create a traveling wave along the basilar membrane, peaking at a specific location that corresponds to the frequency of the sound.

Outlines

00:00

👂 Introduction to the Physiology of Hearing

This paragraph introduces the anatomy of the ear, which is divided into three functionally distinct regions: the external, middle, and inner ear. The external and middle ear structures are involved in hearing, while the internal ear is responsible for both hearing and balance. The outer ear, consisting of the pinna and external auditory canal, collects and amplifies sound. The middle ear, which contains three small bones (malleus, incus, and stapes), transmits sound waves to the inner ear. The inner ear is crucial for converting sound into neural signals and maintaining equilibrium.

05:01

🌀 Structure and Function of the Cochlea

This section explains the anatomy and physiology of the cochlea, the primary organ of hearing. It details how sound waves travel through the cochlea, vibrating the basilar membrane and stimulating hair cells, which convert these vibrations into electrical impulses. The hair cells interact with the tectorial membrane, releasing neurotransmitters that activate auditory nerve fibers. Different frequencies of sound are processed by different parts of the basilar membrane, allowing the brain to interpret the sound.

10:02

⚡ Cochlear Amplification and Frequency Analysis

This paragraph describes the cochlear amplifier, a specialized system where outer hair cells contract and expand to enhance sound sensitivity. It highlights the role of the organ of Corti and its hair cells, which are sensory receptors for hearing. Inner hair cells are fewer but more critical for transmitting sensory input. The spiral ganglion neurons relay electrical signals from the hair cells to the brain, while the basilar membrane acts as a frequency analyzer, responding to different sound frequencies at various locations along its length.

Keywords

💡Outer Ear

The outer ear includes the pinna and the external auditory canal. It collects sound waves and directs them into the external auditory canal. The pinna helps in the localization of sound, while the canal amplifies the sound waves, facilitating the hearing process.

💡Middle Ear

The middle ear is an air-filled space located behind the eardrum and contains three small bones known as ossicles: the malleus, incus, and stapes. These bones amplify sound waves and transmit them from the eardrum to the inner ear, playing a crucial role in the auditory process.

💡Inner Ear

The inner ear is located deep within the temporal bone and consists of the cochlea, vestibule, and semicircular canals. The cochlea is responsible for hearing by converting sound waves into neural signals, while the vestibule and semicircular canals manage balance and equilibrium.

💡Cochlea

The cochlea is the main organ of hearing, converting sound waves into neural signals. It contains fluid-filled chambers and hair cells that respond to sound vibrations, transmitting electrical impulses to the brain. This structure is vital for processing different sound frequencies.

💡Basilar Membrane

The basilar membrane is a thin, flexible membrane inside the cochlea. It vibrates in response to sound waves, causing the hair cells located on it to bend and generate electrical signals. Different frequencies of sound cause vibrations in different parts of the membrane, aiding in sound frequency analysis.

💡Hair Cells

Hair cells are sensory receptors located on the basilar membrane. They convert mechanical vibrations from sound waves into electrical signals that are transmitted to the brain. Outer hair cells amplify sound, while inner hair cells are responsible for transmitting most sensory input to the auditory nerve.

💡Ossicles

The ossicles are three tiny bones in the middle ear (malleus, incus, and stapes) that amplify and transmit sound from the eardrum to the inner ear. Their role in amplifying sound waves is crucial for efficient hearing.

💡Tectorial Membrane

The tectorial membrane is a gel-like structure that overlies the hair cells in the cochlea. When sound vibrations occur, this membrane interacts with the hair cells, causing them to bend and trigger neural signals for auditory perception.

💡Traveling Wave Theory

The traveling wave theory, proposed by Von Bekesy, explains how sound waves create a traveling wave along the basilar membrane. Different parts of the membrane vibrate in response to different frequencies, with high frequencies vibrating near the base and low frequencies vibrating near the apex of the cochlea.

💡Spiral Ganglion

The spiral ganglion contains the cell bodies of sensory neurons that connect with hair cells in the cochlea. These neurons transmit the electrical signals generated by hair cells to the brain, where sound information is processed and interpreted.

Highlights

The ear is divided into three regions: external ear, middle ear, and inner ear, each with distinct roles in hearing and equilibrium.

The outer ear consists of the pinna and external auditory canal, which collect and amplify sound waves.

The middle ear contains three small bones—the malleus, incus, and stapes—which amplify sound and transmit vibrations from the eardrum to the inner ear.

The inner ear contains the cochlea, vestibule, and semicircular canals; the cochlea is crucial for hearing, while the vestibule and canals are responsible for balance.

The cochlea converts sound waves into electrical impulses that are sent to the brain for interpretation.

The cochlea contains three chambers: the scala vestibuli, scala tympani, and scala media, with endolymph in the scala media being rich in potassium ions.

Different sound frequencies cause different regions of the basilar membrane in the cochlea to vibrate, enabling frequency detection.

Hair cells on the basilar membrane, embedded in the tectorial membrane, convert mechanical vibrations into electrical signals via glutamate release.

Outer hair cells in the cochlea amplify sound vibrations, improving hearing sensitivity and frequency selectivity.

The organ of Corti, located in the cochlea, houses hair cells that serve as sensory receptors for sound.

Inner hair cells are primarily responsible for transmitting auditory signals to the brain, while outer hair cells amplify the sound.

95% of sensory neurons innervate the inner hair cells, playing a major role in hearing, while only 5-10% innervate outer hair cells.

The spiral ganglion contains the cell bodies of sensory neurons that transmit electrical signals from the cochlea to the brain.

The basilar membrane's varying stiffness allows it to perform frequency analysis of sound waves, responding differently to high and low frequencies.

Von Békésy's traveling wave theory explains how sound waves create a traveling wave along the basilar membrane, peaking at points corresponding to sound frequency.

Transcripts

[Music]

physiology of

hearing

introduction the ear is divided into

three functionally distinct regions the

external outer ear middle ear and

internal inner ear the external and

middle ear structures are involved in

hearing and the structures of the

internal ear are involved in both

hearing and

equilibrium outer ear the outer ear

consists of the Penna in the external

auditory canal sound waves are collected

by the p and directed into the external

auditory canal the PA helps in

localization of sound while the external

auditory canal amplifies the sound

waves middle ear the middle ear is an

air-filled space located behind the

eardrum the middle ear consists of three

small bones called OES the malus enus

and stapes these bones amplify the sound

waves and transmit them from the e drum

to the inner

ear inner ear the inner ear is located

deep within the temporal bone and the

skull the inner ear consists of the ccka

vestibule and semicircular canals

the ccka is the main organ of hearing

and is responsible for converting sound

waves into neural

signals the vestibule and semicircular

canals are responsible for

balance ccka

physiology ccka is 35 mm long and makes

2 and 3/4 turns the upper Scala

vestibuli and the lower Scala Tony

contain paraly which is rich in sodium

ion the Scala media is the the Middle

cckar Chamber which has stria vascularis

that secretes endolymph which is rich in

potassium ion Scala media is

electrically positive by 85 molt in no

cular potential relative to the Scala

vestibuli and Scala

tempany the ccka is responsible for

converting sound waves into electrical

impulses that are transmitted to the

brain where they are interpreted as

sound sound waves enter the ccka through

the oval window

a membrane that separates the middle ear

from the inner ear as the sound waves

travel through the fluid and the ccka

they cause the Bassel membrane to

vibrate the Bassel membrane is a thin

flexible structure that runs the length

of the ccka and contains thousands of

tiny hair cells that are responsible for

converting sound waves into electrical

impulses the hair cells are embedded in

the tectorial membrane a gel-like

structure that overlies the hair cells

as the Basel membrane V vibrates the

hair cells move back and forth causing

their hair-like projections to bend this

bending of the hair cells triggers the

release of neurotransmitter

glutamate which in turn stimulate the

auditory nerve fibers that are connected

to the hair cells the auditory nerve

fibers then transmit electrical signals

from the ccka to the brain stem where

they are processed in relay to various

parts of the brain for further

processing and

interpretation different frequencies of

sound waves cause different parts of the

Bassel membrane to vibrate which leads

to the stimulation of different

populations of hair cells the location

of the hair cells on the Basel membrane

that are stimulated corresponds to the

frequency of the sound waves the ccka

also has a specialized system for

amplifying sounds called the cockier

amplifier this system involves outer

hair cells in the ccka that are able to

actively contract and expand in response

to electrical signals from from the

brain stem this contraction and

expansion of the outer hair cells

amplifies the vibrations of the Basel

membrane and enhances the sensitivity

and selectivity of the ccka to different

frequencies of

sound the organ of CTI organ of Cy

contains the receptors for hearing hair

cells hair cells are the sensory

receptors of hearing the resting

membrane potential of the hair cells is

about 60 molt hair cells have a motor

protein namely Preston stereocilia and

kinocilia they're named for their

hairlike protrusions which are called

stereocilia kyos cyia on the other hand

are specialized single long cilium found

on one end of the bundle of stereocilia

and some non- mamalian species in

mammals kinocilia are only present

during the early stages of development

and are later lost as the hair cell

matures

stereocilia are arranged in a row of

progressively decreasing height with the

tallest stereocilium located at one end

of the bundle and the shortest at the

other end they're connected to each

other by fine elastic structures called

tip links these tip links contain

mechanically sensitive cat ion channels

which are channels that allow positively

charged ions such as potassium and

calcium to flow into the cell when

they're activated by mechanical

forces when sound waves enter the inner

ear and cause the stereo cyia to bend

the tip links stretch and pull on the

mechanically sensitive cat ion channels

opening them up and allowing ions to

flow into the hair cell def flection of

the stereocilia toward the kyum opens

the potassium channels depolarizing the

inner hair cell and causing the influx

of calcium that stimulates the release

of the neurot transmitter glutamate

which then stimulates the aper neurons

to transmit neural impulses to the

auditory cortex at rest the potassium

channels are partially

[Music]

open therefore deflection of stereocilia

toward the shortest stereocilia closes

the potassium channels and inhibits

signal transmission by the afrite

neurons outer and inner hair cells the

hair cells in the organ of CTE are

arranged in four rows with the three

rows of outer hair cells and one row of

inner hair

cells the outer hair cells are more

numerous with about 20,000 cells while

the inner hair cells are fewer in number

with only around 3500 cells however

despite being fewer in Number the inner

hair cells are more important for

hearing as they're responsible for

transmitting the majority of the sensory

input from the hair cells to the

auditory nerve fibers the the outer hair

cells play a critical role in amplifying

The Sound signals before they're

transmitted to the auditory nerve fibers

note 95% of these Sensory neurons

innervate the inner hair cells only 5 to

10% innervate the outer hair cells the

spiral gangion the spiral gangion

contains the cell bodies of the sensory

neurons that inate the hair cells of the

organ of Cy these Sensory neurons are

known as spiral gangan neurons and they

form sinaps es with the hair cells that

transmit the electrical signals

generated by the hair cells to the brain

the spiral ganglia neurons are bolar

neurons with one dendrite that synapses

with the hair cells and one axon that

extends to the brain stem where it

synapses with other neurons in the

auditory pathway the spiral gangan

neurons are essential for transmitting

the sensory information from the organ

of qute to the brain where it's

processed and interpreted as

sound roll a Bassler membrane in hearing

process the frequency

analyzer the Bassler membrane is a

critical component of the hearing

process playing a vital role in the

frequency analysis of sound waves the

Bassler membrane is a thin flexible

membrane that runs the length of the

ccka and separates the fluid-filled

chambers of the ccka into two

compartments when sound waves enter the

ccka they create waves in the

fluid-filled chambers that cause the

Bassel membrane to vibrate the Bassel

membrane is stiffer at the base of the

ccka near the oval window and becomes

more thin and flexible towards the apex

of the cocka as a result different

frequencies of sound waves cause maximum

displacement at different points along

the length of the Bassel membrane with

higher frequencies causing maximum

displacement near the base of the ccka

and lower frequencies causing maximum

displacement near the Apex this

frequency analysis is important because

it allows the auditory system to

distinguish between different

frequencies of sound waves and identify

the pitch of the

sound the hair cells of the organ of CTI

are located on the Bassel membrane and

they respond to the mechanical

vibrations of the Basel membrane by

generating electrical signals that are

transmitted to the brain the spatial

arrangement of the hair cells on the

Bassel membrane corresponds to the

frequency analysis with the Heros cells

at the base of the ccka responding to

high frequency C sounds and the hair

cells at the Apex responding to low

frequency sounds this gives the

appearance of a traveling wave in

Bassler membrane this series called

traveling wave theory of Von

Becki traveling wave theory of Von Becki

according to the traveling wave theory

when sound waves enter the ccka they

create a traveling wave that moves along

the Bassler membrane from the base of

the ccka near the oval window to the

apex of the

ccka the wave Peaks at a specific

location along the Bassel membrane that

corresponds to the frequency of the

sound wave with higher frequencies

causing maximum displacement near the

base of the ccka in lower frequencies

causing maximum displacement near the

Apex as a traveling wave moves along the

Basel membrane it causes the hair cells

to bend and generate electrical signals

that are transmitted to the brain the

outer hair cells of the organ of quarty

play a critical role in amplifying The

Traveling wave and enhancing the

sensitivity and selectivity of the

auditory

system that's all for the video we'll

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