The Beating Eardrum!
1. External Ear (Pinna)
2. Ear Canal
3. Middle Ear
4. Inner Ear
5. Eustacian Tube
2. Ear Canal
3. Middle Ear
4. Inner Ear
5. Eustacian Tube
How Do We Hear?
The Middle Ear
Before you can
understand how
we possess the ability to hear you must first understand what the ear
consists of. In
totality, the ear consists of an external ear, a middle ear, and an
inner ear. For our purposes we will focus on the middle and inner ear
because these are the two most important divisions of the ear that
enable us to hear.The Middle Ear
Primarily, the middle ear is located between the external ear and the inner ear and consists of bones and muscles. These bones are known as the ossicles and are connected to the tympanic membrane (eardrum).
The ossicles are referred to as the malleus (for its hammer shape), the incus (for its anvil shape), and the stapes. There are two muscles within the inner ear and they are known as the tensor tympani and the stapedius.
Working together, the ossicles, tympanic membrane, tensor tympani, and the stapedius process and send infomation to the inner ear. When exposed to a stimuli the middle ear amplifies sound pressure in order to stimulate the fluid filled inner ear.
The Inner Ear
Now
that you understand that the middle ear processes and sends stimuli to
the inner ear we can further our discussion about the processing of
sound. The inner ear is ultimately responsible for converting sound
into neural activity.
The main portion of the inner ear is known as the cochlea which is located in the temporal lobe of the encephalon (brain) and is approximately the size of a pea!
The cochlea (think of a fruit roll up) consists of the vestibular canal, the middle canal, and the tympanic canal (think of three different colored fruit roll ups rolled up into one).
Another significant portion of the inner ear is known as the organ of Corti which consists of hair fibers that contain sensory cells. The basilar membrane is known to neuroanatomists as the "base of the organ of Corti" which vibrates in response to sound. This "displacement" of the basilar membrane, which is dependent on the frequency of the sound, sends auditory information to the IHCs (inner hair cells) and the OHCs (outer hair cells).
The result of this process (stimulation of the organ of Corti ) results in an "action potential" which is, for our discussion purposes, the processing of information within the encephalon. These action potentials are very vigorous occurring approximately 1,000 times per second! The final result of this amazing process is the ability to hear!
The main portion of the inner ear is known as the cochlea which is located in the temporal lobe of the encephalon (brain) and is approximately the size of a pea!
The cochlea (think of a fruit roll up) consists of the vestibular canal, the middle canal, and the tympanic canal (think of three different colored fruit roll ups rolled up into one).
Another significant portion of the inner ear is known as the organ of Corti which consists of hair fibers that contain sensory cells. The basilar membrane is known to neuroanatomists as the "base of the organ of Corti" which vibrates in response to sound. This "displacement" of the basilar membrane, which is dependent on the frequency of the sound, sends auditory information to the IHCs (inner hair cells) and the OHCs (outer hair cells).
The result of this process (stimulation of the organ of Corti ) results in an "action potential" which is, for our discussion purposes, the processing of information within the encephalon. These action potentials are very vigorous occurring approximately 1,000 times per second! The final result of this amazing process is the ability to hear!
Why
Can't Some People Hear?
Sadly, the inability to hear is a significant disability that individuals face within our society. However, on a brighter note, technological and medical advances are offering hope to those suffering from this disability. Let's take a look at why individuals are unable to hear.
For our purposes the inability to hear is referred to as "deafness" by the medical community and there are three types of deafness that we will explore. The three commonly diagnosed types of deafness are conduction deafness, sensorineural deafness, and central deafness.
Conduction deafness results when disorders of the middle ear prevent vibrations from reaching the cochlea. Primarily, the ossicles become fused and can no longer transmit sound vibrations effectively.
The second type of deafness is Sensorineural deafness. The maladaptive neurobiological processes that result in Sensorineural deafness is a bit more complex than that of Conduction deafness. Briefly, auditory nerve fibers are unable to become excited in a normal manner which results in a hearing impairment for the individual.
The final type of deafness is Central deafness. Central deafness is generally caused by brain lesions and strokes. Commonly, individuals who have been diagnosed with the Central deafness disorder retain their ability to hear but lose their ability to recognize spoken words.
Click here for a diagram of the Auditory Cortex
Sadly, the inability to hear is a significant disability that individuals face within our society. However, on a brighter note, technological and medical advances are offering hope to those suffering from this disability. Let's take a look at why individuals are unable to hear.
For our purposes the inability to hear is referred to as "deafness" by the medical community and there are three types of deafness that we will explore. The three commonly diagnosed types of deafness are conduction deafness, sensorineural deafness, and central deafness.
Conduction deafness results when disorders of the middle ear prevent vibrations from reaching the cochlea. Primarily, the ossicles become fused and can no longer transmit sound vibrations effectively.
The second type of deafness is Sensorineural deafness. The maladaptive neurobiological processes that result in Sensorineural deafness is a bit more complex than that of Conduction deafness. Briefly, auditory nerve fibers are unable to become excited in a normal manner which results in a hearing impairment for the individual.
The final type of deafness is Central deafness. Central deafness is generally caused by brain lesions and strokes. Commonly, individuals who have been diagnosed with the Central deafness disorder retain their ability to hear but lose their ability to recognize spoken words.
Click here for a diagram of the Auditory Cortex
NOW YOU CAN MAKE YOUR OWN
EARDRUM!!!!!!
Now
that you
have learned about the major functions of the processing of auditory
information by the ear you can make your own eardrum. It is really
simple to make your own eardrum, all that you need is a bowl, plastic
wrap, rice, and a radio!
*Tightly wrap the plastic wrap around the top of the bowl.
*Place 20-30 rice grains on top of the plastic wrap covering the bowl.
*Now with your favorite music playing, place the boom box next to your bowl. The sound waves from the boom box will cause the rice to vibrate on the plastic wrap, just like sound waves cause your ear drum to vibrate.
*You can demonstrate how ear infections work by filling up your bowl with shaving cream. Now when you put the boom box up to the bowl the rice grains do not jump up and down.
*Place 20-30 rice grains on top of the plastic wrap covering the bowl.
*Now with your favorite music playing, place the boom box next to your bowl. The sound waves from the boom box will cause the rice to vibrate on the plastic wrap, just like sound waves cause your ear drum to vibrate.
*You can demonstrate how ear infections work by filling up your bowl with shaving cream. Now when you put the boom box up to the bowl the rice grains do not jump up and down.
Materials:
4" to 20" in diameter sturdy bowls
plastic wrap
shaving cream
uncooked rice
boom box
STUDENT
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*This website was brought to you by: The University of Scranton, Society for Neuroscience, Kids Judge, Dr. Timothy Cannon (UofS), Jenelle Janowicz (UofS), Laura Farrelly (UofS), and Paul Joseph Pavalone (UofS). Thank you for visiting and come again!