039 The Function of the Organ of Corti

Summary

In this episode of Interactive Biology TV, Leslie Samuel explains the function of the organ of Corti within the cochlea. He discusses how sound waves cause vibrations that move through the ear, eventually vibrating the basilar membrane, which moves the organ of Corti. This movement bends hair cells' cilia, sending signals to the brain via the auditory nerve. Inner hair cells directly help with hearing, while outer hair cells modulate the response. The episode features a demonstration of hair cells vibrating in response to sound, illustrating their role in hearing.

Takeaways

• 🎥 The episode focuses on the function of the organ of Corti, a crucial structure in the ear responsible for hearing.
• 👂 Sound waves enter the ear, causing the tympanic membrane to vibrate, which then transfers the vibrations through the malleus, incus, and stapes bones, and finally into the fluid inside the cochlea.
• 🌀 The cochlea is unrolled to demonstrate how different frequencies are detected based on where vibrations occur along its structure, sending signals to the brain to interpret sound pitch.
• 🔍 The cochlea is divided into three sections: scala vestibuli, scala tympani, and the cochlear duct, with the basilar membrane separating the scala vestibuli and scala tympani.
• 🧠 The organ of Corti sits on top of the basilar membrane and is crucial for translating sound vibrations into neural signals.
• 🌊 When the basilar membrane vibrates, it causes the organ of Corti to move, which in turn moves the tectorial membrane in a windshield-wiper motion.
• 🎋 The movement of the tectorial membrane bends the cilia of hair cells in the organ of Corti, creating electrical signals that are sent to the brain via the auditory nerve.
• 🔊 Inner hair cells are responsible for sending sound signals to the brain, while outer hair cells modulate the response, enhancing hearing sensitivity.
• 🎶 The video included shows the outer hair cells vibrating in response to sound, demonstrating their role in modulating hearing.
• 📚 The host encourages viewers to leave comments with questions and visit the website for more biology resources and videos.

Q & A

What is the main topic of the video?

The main topic of the video is the function of the organ of Corti in the ear and how it is involved in the process of hearing.

What are the roles of the inner and outer hair cells in the organ of Corti?

The inner hair cells are directly responsible for sending hearing signals to the brain, while the outer hair cells modulate the response of the inner hair cells, helping to enhance hearing.

How does the basilar membrane affect the organ of Corti?

When the basilar membrane vibrates up and down, it causes the organ of Corti to move in the same manner, which then affects the tectorial membrane and the hair cells within the organ of Corti.

What is the tectorial membrane, and what role does it play?

The tectorial membrane is a membrane located above the organ of Corti. It moves in a windshield-wiper-like fashion when the basilar membrane vibrates, which in turn causes the cilia on the hair cells to bend, initiating a signal to be sent to the brain.

What is the significance of the cochlear duct mentioned in the video?

The cochlear duct is an important structure within the cochlea that houses the organ of Corti. It plays a crucial role in the hearing process by containing the organ responsible for translating sound vibrations into neural signals.

What happens when the cilia of the inner hair cells bend?

When the cilia of the inner hair cells bend, it triggers a signal to be sent via the auditory nerve to the brain, allowing the perception of sound.

What is the difference between the scala vestibuli and the scala tympani?

The scala vestibuli is the upper cavity of the cochlea, while the scala tympani is the lower cavity. Both are fluid-filled chambers that help transmit sound waves through the cochlea.

Why is it important that the outer hair cells modulate the response to sound?

The modulation by the outer hair cells enhances the sensitivity and precision of hearing by fine-tuning the response of the inner hair cells to different frequencies and intensities of sound.

What visual aids does the speaker use to explain the structure of the cochlea?

The speaker uses diagrams and cross-sectional images of the cochlea to show the placement of structures such as the organ of Corti, basilar membrane, tectorial membrane, and the different scala.

How does the movement of the basilar membrane influence the tectorial membrane and the hair cells?

As the basilar membrane moves up and down, it causes the tectorial membrane to move in a sweeping motion. This movement bends the cilia on the hair cells, leading to the initiation of electrical signals that are sent to the brain.

Outlines

00:00

🎙️ Introduction to Episode 39: The Organ of Corti

In this episode of Interactive Biology TV, Leslie Samuel introduces episode 39, which focuses on the function of the organ of Corti. He mentions his previous episode (38) where he sang, but reassures viewers that there will be no singing in this episode. He begins with a brief recap of how sound waves cause vibrations in the ear, leading to signals being sent to the brain. Samuel explains the structure of the cochlea, focusing on its chambers: the scala vestibuli and scala tympani. He promises to delve deeper into the function of the organ of Corti in this episode.

05:05

🔬 Understanding the Structure of the Cochlea

Leslie Samuel takes a cross-section view of the cochlea, explaining the layout in more detail. He describes the basilar membrane and the organ of Corti situated above it. He shows how the cochlea’s chambers (scala vestibuli and scala tympani) and the cochlear duct are positioned. Special attention is given to the organ of Corti, which is central to the episode. Samuel introduces the tectorial membrane, noting how it moves in response to vibrations from sound waves and interacts with the organ of Corti, setting the stage for further exploration.

🎵 The Role of Hair Cells in Hearing

Samuel discusses the crucial components of the organ of Corti: inner and outer hair cells. He explains how sound causes the basilar membrane to vibrate, which moves the tectorial membrane in a windshield wiper-like motion. This movement bends the hair cells' cilia, sending signals to the brain. Inner hair cells are responsible for hearing, while outer hair cells help modulate the response, enhancing hearing sensitivity. Samuel emphasizes the role of both types of hair cells in processing sound, explaining their individual and combined contributions to hearing.

🎶 Outer Hair Cells Modulating Sound Response

A video demonstration shows outer hair cells vibrating in response to sound, a process that helps modulate hearing. Samuel emphasizes how this vibration assists in shaping the signal that reaches the brain, ensuring a clearer perception of sound. The video illustrates the dynamic interaction between hair cells and sound waves, offering viewers a visual representation of how the hearing mechanism works. Samuel closes by encouraging viewers to leave comments and visit the website for more biology content.

Keywords

💡Organ of Corti

The organ of Corti is the main structure responsible for hearing, located on the basilar membrane inside the cochlea. It contains hair cells that detect sound vibrations and convert them into electrical signals that are sent to the brain. The video discusses the organ of Corti’s role in responding to vibrations caused by sound waves, which are crucial for the process of hearing.

💡Basilar Membrane

The basilar membrane is a structure within the cochlea that vibrates in response to sound waves. It forms the base upon which the organ of Corti sits. In the video, the movement of the basilar membrane causes the organ of Corti to move up and down, which initiates the process of converting sound into neural signals.

💡Tectorial Membrane

The tectorial membrane is a gel-like structure that lies above the organ of Corti. As sound waves cause the basilar membrane to vibrate, the tectorial membrane moves in a windshield-wiper motion, bending the hair cells on the organ of Corti. This bending triggers the auditory signal that gets sent to the brain. In the video, its movement is described as key to transmitting sound vibrations to the hair cells.

💡Inner Hair Cells

Inner hair cells are the primary sensory cells in the organ of Corti responsible for converting sound vibrations into electrical signals. These signals are then transmitted to the brain via the auditory nerve. The video emphasizes their central role in hearing, distinguishing them from outer hair cells, which assist in fine-tuning the auditory response.

💡Outer Hair Cells

Outer hair cells are involved in modulating the response of the inner hair cells, enhancing the sensitivity and precision of hearing. In the video, these cells are shown vibrating in response to sound, contributing to the fine-tuning of sound perception. They play a supporting role in amplifying and refining the auditory signal sent to the brain.

💡Cochlea

The cochlea is the spiral-shaped, fluid-filled part of the inner ear where sound vibrations are transformed into electrical signals. The video explains how the cochlea's fluid vibrates due to incoming sound waves, and these vibrations affect different parts of the basilar membrane, depending on the frequency of the sound. This variation allows the brain to interpret different pitches.

💡Sound Waves

Sound waves are vibrations that travel through the air and are detected by the ear. In the video, sound waves enter the ear and cause vibrations in the tympanic membrane, which then lead to the movement of the ossicles and the cochlea’s fluid. These waves ultimately cause the basilar membrane to move, triggering the process of hearing.

💡Auditory Nerve

The auditory nerve transmits electrical signals from the inner hair cells of the organ of Corti to the brain, where they are interpreted as sound. The video discusses how bending of the cilia in the inner hair cells sends signals via the auditory nerve, allowing the brain to perceive sound.

💡Cilia

Cilia are tiny hair-like structures on the hair cells of the organ of Corti. When the tectorial membrane moves, it causes the cilia to bend, which in turn triggers the hair cells to send electrical signals to the brain. The video highlights how this bending is a crucial step in the process of hearing, as it directly leads to the generation of auditory signals.

💡Pitch

Pitch refers to the perceived frequency of a sound, which is determined by where the basilar membrane vibrates along its length. In the video, it is explained that different parts of the cochlea are sensitive to different frequencies, allowing the brain to interpret the pitch of the sound based on which part of the basilar membrane is vibrating.

Highlights

Introduction to the organ of Corti and its function in the auditory system.

Explanation of how sound waves cause the tympanic membrane to vibrate, initiating a chain reaction leading to cochlear fluid vibration.

Review of the cochlear structure and the role of different parts, including the scala vestibuli and scala tympani.

Cross-sectional view of the cochlea showing the relative position of the organ of Corti, basilar membrane, and cochlear ducts.

Introduction of the tectorial membrane and its windshield-wiper motion caused by basilar membrane vibrations.

Identification of inner and outer hair cells in the organ of Corti, and how they contribute to the auditory process.

Inner hair cells are primarily responsible for sending signals to the brain, facilitating hearing.

Outer hair cells modulate the response of the inner hair cells, improving hearing sensitivity.

Description of how sound-induced vibrations cause the cilia of hair cells to bend, sending auditory signals to the brain.

Importance of the basilar membrane’s up-and-down motion in driving the process of hearing.

Detailed function of the tectorial membrane’s windshield-wiper-like motion in activating the outer hair cells.

The role of the auditory nerve in transmitting signals from the inner hair cells to the brain for sound interpretation.

Explanation of how outer hair cells enhance the response to sound by vibrating in response to certain frequencies.

A demonstration video showing how outer hair cells vibrate in response to sound waves, visually illustrating their role in the auditory process.

Closing remarks encouraging viewers to leave comments and visit the website for more biology resources.

Transcripts

hello and welcome to another episode of

interactive biology TV where we're

making biology fun my name is Leslie

Samuel and in this episode episode 39

I'm gonna be talking about the function

of the organ of Corti and don't worry I

won't be singing in this episode

that's episode 38 so if you want to hear

me sing go to episode 38 and enjoy today

we're just gonna talk about the function

of the organ of Corti so let's get right

into it now we've been looking at this

picture and we've been looking at the

structure of the air we look at the fact

that sound waves come in here cause the

vibration in the tympanic membrane

causing the malleus incus and step is to

vibrate and then causing the fluid

inside of the cochlea to vibrate in the

last episode we unrolled the cochlea and

we looked at it like this and we showed

that depending on where it vibrates

that's gonna send signals to the brain

and the brain can interpret that as a

certain pitch a certain frequency now

there are a few things that I want you

to pay attention to in this episode that

we did not pay attention to in the

previous episodes and that would be here

we have the scaler vestibuli that's this

cavity at the top here and below the

basilar membrane we have the scaler

tympani and that's the cavity at the

bottom of the cochlea beneath the

basilar membrane and what I'm gonna do

in the next picture is I'm gonna

actually take a cross-section so I'm

gonna cut straight through the cochlea

like this and we're gonna look at a

cross-section of the cochlea so let's go

to the next figure here we're looking at

a cross-section of the cochlea and here

you can see we have the scalar

vestibular

and here we have the scaler tempani the

scaler

tympani and here this is the basilar

membrane and right above the basilar

membrane we have the organ of Corti so

that's this section right here we can't

see too many details about it but that

is the organ of Corti here we can see

more details this entire structure is

the organ of Corti but I just want you

to pay attention to how its laid out

here with the organ of Corti hair scale

of vestibuli at the top this is the

basilar membrane and here we have the

scaler tympani one more place that I

want you to pay attention to here is

another cavity we call the cochlear duct

and once again in here we have the organ

of Corti so this is a cross-section of

the cochlea and that's how it's laid out

now I want to bring your attention to

the organ of Corti which is shown

clearly right here once again we can see

here we have the basilar membrane and on

top of that we have the organ of Corti a

few more things to point out here this

membrane here it says the membrane

attack Toria we call that the tectorial

membrane

and we looked at the fact that when

sound enters the cochlea that causes the

basilar membrane to vibrate up and down

now when that vibrates up and down

that's gonna cause the organ of Corti to

move up and down then here we have the

tectorial membrane that's attached only

at one end so as the basilar membrane is

going up and down in the organ of Corti

is going up and down that is gonna cause

the tectorial membrane to move in a

windshield-wiper

like flash fashion so it's just gonna

flap like a windshield wiper now on the

organ of Corti in the organ of Corti we

have a number of different hair cells we

have inner hair cells which would be

this one here and we have outer hair

cells which would be these four here now

as you can imagine if the entire organ

of Corti is moving up and down the

tectorial membrane is moving in a

windshield wiper like fashion that

tectorial membrane is gonna cause this

outer part of the hair cells to vibrate

and these outer parts are called cilia

so it's gonna cause the cilia to bend

and that's the process that's gonna

cause a signal to go via the auditory

nerve to the brain now there's a very

important thing to understand here the

part that responds to the tectorial

membrane that is directly responsible

for hearing would be the inner hair

cells and that sends a signal to the

brain however the outer hair cells are

involved in modulating the response and

helping the inner hair cells so that you

can hear better so once again when the

sound comes into the cochlea the basilar

membrane

I braids up and down that causes the

tectorial membrane to move in a

windshield wiper like fashion causing

the cilia and the hair cells to bend and

when the cilia and the inner hair cells

Bend that causes a signal to be sent to

the brain the outer hair cells are

involved in modulating the response to

that sound now I have a very fascinating

video to show you that's gonna show what

happens to the outer hair cells in

response to sound so sit back relax and

enjoy the ride

one two three o'clock four o'clock rocks

five six seven o'clock eight o'clock

Rock ten eleven o'clock twelve o'clock

rock we're gonna rock

[Music]

[Music]

so as you can see in a very interesting

way this hair cell was vibrating up and

down it was vibrating in response to the

sound and that process is involved in

modulating the response to hearing this

causes signals to be sent to the brain

and the brain gets a full picture of the

sound that you're listening to that's it

for this video if you have any questions

as usual leave them in the comment

section below and you can always visit

the website at interactive - biology

comm for more biology videos and other

resources that's it for now and I'll see

you in the next one

you