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Course: Health and medicine > Unit 8
Lesson 7: Sound (Audition)Cochlear implants
Created by Ronald Sahyouni.
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You say that nerve deafness prevents transmission of the signal from the cochlea to the auditory nerve, and then say that the signal from the cochlear implant (more specifically the stimulator) relays the signal to the cochlea. But the problem, as stated, is transmission between cochlea and nerve. You see what I am saying? As you explain it, hearing loss will still persist.(109 votes)
My understanding of cochlear implants is that they are designed to overcome an issue in which the hairs within the cochlea are not able to transmit the action potential to the nerve axons that feed into the auditory nerve. The implant stimulator stretches into the cochlea and directly stimulates these nerves, removing the need for the hair cells to accomplish this part of the pathway. Since the stimulator can't reach all the way to the apex of the cochlea, and therefore can only directly stimulate some of the nerve axons that stretch into the auditory nerve, the sound that is generated from cochlear implants is not exactly the same as natural sound.(62 votes)
At2:50, he says that the cochlea converts the electrical impulse from the stimulator into a nerve impulse. How does it do that?(9 votes)
Directly from Wikipedia (http://en.wikipedia.org/wiki/Cochlear_implant#Functionality):
"The cochlear implant bypasses the hair cells and stimulates the cochlear nerves directly using electrical impulses. This allows the brain to interpret the frequency of sound as it would if the hair cells of the basilar membrane were functioning properly"(15 votes)
At1:01, you said the individual has a problem with conduction. How does one determine it is a conduction issue as opposed to something else?(4 votes)
There is probably a very specific way that they would do it if you went to an ear doctor, but you can get a good idea of wether hearing loss is caused by conduction or if it is caused by other hearing loss by using a tuning fork. You can hit the tuning fork, and then place it on the very top of your head and listen to which ear it sounds loudest in. If you had something in your ear (blocking sound transmission) then this is the ear that the tuning fork would sound the loudest in. (you would have to double check this with something called the Rinne Test - http://en.wikipedia.org/wiki/Rinne_test : but that is where it becomes a little complicated)(6 votes)
If the deficit is the neuronal transmission to the brain, then how does the transplant assist this deficit? The transplant still leads up to the same issue: the neuronal impulse not being delivered to the brain., because if something is wrong with the person's nerves, then the transplant can't help the issue because the transplant stops at the middle ear when the issue is with the inner ear(6 votes)
What is the piece that is on top of the hole into the ear and connected to the speech processor? He never mentioned that part in the video.(5 votes)
It is called a T-Mic, and it receives the sound waves, and sends it to the processor to process(1 vote)
- How come the neural impulse goes to the cochlea, isn't the neurons there defective?(4 votes)
- To clear out...is it true that nerve deafness cannot convert from soundwave to electrical impulse rather than converting electrical impulse to neural impulse?(1 vote)
- In a person with normal hearing ability, soundwaves are first converted into mechanical vibrations in the cochlear fluid. This causes movement of hair cells in the organ of corti. This in turn results in opening of K+ ion channels. Then there is opening of calcium ion channels. This represents conversion of soundwaves into electrical impulse.
Later, these electrical impulses cause excitation of auditory nerve thus generating nerve impulse.
In nerve deafness,there may be no opening of either potassium or calcium ion channels. thus, conversion may be hampered at either of the two stages.(3 votes)
how does microphone turn sound waves into electrical signal? (if u know any video explaining this please link, TQ)(0 votes)
By Faraday's Law of Induction. If you go to the Wikipedia page for 'Microphone' they explain the principles better than I could(5 votes)
if the device has its own microphone what is the bit in the patients ear?(1 vote)- He says sensory narrow hearing loss. Isn't it sensorineural hearing loss?(0 votes)
He says 'sensorineural' but you hear it as 'sensory narrow'.(3 votes)
2:50Video transcript
In this video, we're gonna talk about cochlear implants. Now, cochlear implants are basically a surgical procedure that
attempts to restore some degree of hearing,
of the ability to hear, to individuals that
have something known as sensorineural hearing loss. And this is otherwise
known as nerve deafness. So let's talk about sensorineural hearing loss real quick. So normally what we have is, we have sound waves coming in, they hit the ear. And then they travel
through this auditory canal, cause the eardrum to
vibrate back and forth, and this vibration
causes these three little bones in the middle ear
to vibrate back and forth. And eventually, fluid moves back and forth in the cochlea, and that
fluid movement gets, stimulates hair cells that then produce an electrical signal that
gets sent to the brain. Now individuals with
sensorineural hearing loss, this conversion over here
basically does not work. So there's a problem with conduction. And this can be surgically treated with something known as a cochlear implant. You know what, let me
just write that down, so, "Cochlear implant." So let's talk about a cochlear implant. Let's just look at the
different components of the cochlear implant. So, this implant part, which
is what I'm highlighting right here, is known as a receiver. And then from the
receiver extends this long kind of tube that goes all the way into the cochlea and turns around like that, and this tube is known as a stimulator. Now, what is the receiver doing? It's receiving information from this wall structure right here, and this is known as a transmitter. So the transmitter. And the transmitter is getting electrical information from this thing that I'm highlighting now, which is known as a speech processor. Speech processor. The speech processor
basically gets information through this little opening,
which is the microphone. So as sound waves come in,
they hit the microphone, and the microphone takes the sound waves, converts them into an electrical impulse, which then gets sent to the transmitter, which you can see it some, it's outside of the individual's skull. And the transmitter sends that information to the receiver, which is inside, it's implanted inside the patient's skull. Then the receiver sends the information through the stimulator, into the cochlea, and then the cochlea converts that electrical impulse into a neural impulse that goes down the auditory
nerve into the brain in order for that sound
wave to be processed. And so basically, this
effectively restores some degree of hearing to individuals with nerve deafness.