Aural Anaphysio Flashcards
What is the main function of the outer ear?
Sound funnel
Resonation
What is the function of the auricle or pinna?
The auricle or pinna, which funnels the sound to the ear canal helps localize sound (this is the most visible part of the ear and is composed primarily of cartilage)
What is the concha?
It is the entrance to the ear canal
Shell
How long is the external auditory meatus?
7 mm diameter
2.5 cm long, + 1.5 cm from tragus
What is the external auditory meatus made of?
lateral 1/3: cartilage
Medial 2/3: osseous-bony structure (temporal bone)
This selectively enhances sound
outer ear
What is the range where it is enhanced by outer ear?
sounds that are 1500 - 8000 Hz
What is the main function of the middle ear?
Answer: Increase the pressure towards the cochlea through impedance matching
Rationale
Impedance Matching:
The middle ear serves to match the high impedance of the fluid-filled cochlea to the low impedance of the air in the outer ear.
Sound travels through air, which has low impedance, but when it enters the cochlea (filled with fluid), it encounters higher impedance. If sound were transmitted directly from air to the fluid without amplification, much of the sound energy would be reflected rather than transmitted, leading to significant hearing loss. The ossicular chain (comprising the malleus, incus, and stapes) amplifies the sound vibrations from the tympanic membrane (eardrum) to the oval window (the entrance to the cochlea).
The malleus is larger than the stapes, which acts like a lever system:
The difference in size between the tympanic membrane (where the malleus is attached) and the oval window creates a pressure increase.
The surface area of the tympanic membrane is much larger than that of the oval window, allowing for an increase in pressure as the sound vibrations are transmitted.
Among the three bones of the ossicular chain, which one is the largest?
Malleus
Rationale: The first and largest of the three bones is the malleus (latin for hammer) because it resemble a hammer. One end of the malleus is embedded in the tympanic membrane. Because of this attachment, the vibrations of the tympanic membrae are transmitted to the malleus.
This bone in the middle ear is called the anvil. What is the name of this bone?
Incus
This is the border between the outer ear and middle ear
tympanic membrane
What is the tympanic membrane made of?
Composed of 3 layered sheets–epithelial lining of the EAM as the outer layer, middle layer (connective tissue that provides structure to the TM), inner layer is the lining of the middle ear
What is the main function of tympanic membrane?
transmits and amplifies the sound;
it transmits the sound from the outside coming into the inside and initates mechanical action of your ossicular chain/ middle ear.
Rationale
Vibration Response: The tympanic membrane vibrates in response to sound waves that enter the ear canal. These vibrations correspond to the frequency and amplitude of the incoming sound.
Transfer of Vibrations: The tympanic membrane transmits these vibrations to the ossicular chain (the malleus, incus, and stapes) in the middle ear, initiating the process of sound amplification.
When sound waves hit the tympanic membrane, it vibrates in response to the frequency and amplitude of the sound.
This vibration converts the airborne sound energy into mechanical energy.
This is the soft part of the tympanic membrane
Pars flaccida
What is the area of the tympanic membrane
55 m^2
What is impedance matching?
Impedance matching, we are trying to regulate the input coming into the ear in such a way that there is increasing force coming into the cochlea.
Impedance matching refers to the mechanism by which the outer and middle ear amplify and transfer sound waves effectively to the inner ear, where sound is converted into electrical signals for the brain to interpret
What is the first impedance matching?
Decreasing area
Rationale
Tympanic Membrane (55 mm2) vs Oval Window (3.2 mm2) (Inner Ear)
The tympanic membrane has a larger surface area compared to the oval window (about 20 times larger). This area difference results in an increased pressure on the oval window when the same force is applied, effectively amplifying the sound signal.
This alone provides a gain of approximately 25 dB (17:1).
Why is the area difference between the tympanic membrane and oval window important?
The tympanic membrane is significantly larger compared to the oval window, because this acts to increase pressure, effectively transferring energy more efficiently from the larger surface of the eardrum to the smaller surface of the oval window–greater pressure is generated on the surface with the smaller area.
What is the malleoincudal joint?
It is the saddle joint
Limited movement
The malleus and incus are connected in a tight joint (malleoincudal joint) that permits very little movement.
This provides a connection to the middle ear and inner ear
Footplate of the stapes
True or False. The footplate is the same size as the oval window
True (3.5 mm^2)
What is the second impedance matching?
Lever difference.
Manubrium (9mm) vs Long Process (7mm) = 2 dB
If the Manubrium and the Long process move, the force that’s produced at the end of the long process is amplified. This is because the manubrium is longer so the force that the long process receives is greater.
What is the least impedance matching?
Lever difference (2 dB)
What is the third impedance matching? What happens during the third impedance matching?
Tympanic Membrane Buckling
If the tympanic membrane receives sound, it will BUCKLE inward (like the photo above) while the manubrium pulls the TM inward as well.
Basically, the TM and the Malleus buckles. As they buckle, the distance traveled by the TM is longer than the Malleus.
Force Increase = 4-6 dB
When the tympanic membrane receives sound, it buckles inward, and the manubrium of the malleus is pulled inward as well. The distance the tympanic membrane travels is longer than the malleus, creating a mechanical advantage that results in a force increase of 4-6 dB. This contributes to the overall efficiency of sound transmission to the inner ear.
How much is the force increase of the third impedance matching?
4-6 dB
Why is impedance matching important?
Impedance matching is important in auditory systems because it helps to efficiently transfer sound energy from the air (which has low impedance) to the fluid-filled inner ear (which has high impedance).
How much is the total signal gain in impedance matching?
Total Signal Gain = ~31 dB
The tensor tympani is innervated by what cranial nerve? How about the stapedius muscle?
The tensor tympani is innervated by the CN V while the stapedius muscle is innervated by the CN VII
Where is the origin of the stapedius muscle?
Temporal bone
Where is the origin of the tensor tympani?
Eustachian tube/sphenoid bone
Where is the insertion of the stapedius muscle?
Post crus (stapes)
Where is the insertion of the tensor tympani?
Manubrium of the malleus
What is the function of the stapedius?
It rotates the footplate of your stapes posteriorly
They reduce the distance of the entire ossicular chain.
Protective for loud sounds–The stapedius muscle stiffens the ossicular chain so that its vibrations are reduced.
What is the function of the tensor tympani?
Pulls malleus anteriorly
They reduce the distance of the entire ossicular chain
Protective for loud sounds–the tensor tympani muscle tenses the tympanic membrane so that the vibrations are reduced
When a person hears very loud noises that could damage the ears, the middle ear muscles contract in a reflexive action called
When a person hears very loud noises that could damage the ears, the middle ear muscles contract in a
reflexive action called the acoustic reflex. The acoustic reflex stiffens the middle ear system, especially
the tympanic membrane.
What does the eustachian tube do?
Aeration of the middle ear space
Maintains equilibrium between middle ear and atmospheric pressure
What activates the eustachian tube?
Tensor veli palitini
The inner ear houses 2 sensory systems. What are they?
Vestibular system
Cochlea (hearing)
The inner ear consists of two labyrinths: What are the 2 labyrinths? Explain that each structure contains
Osseous (Petrous Portion of T Bone)
Membranous
The osseous (bony) labyrinth and the membranous labyrinth.
This is the entryway to the cochlea
Vestibule
Space for the middle ear
Round window
They are the sensory organs to detect balance
Semicircular canals
This semicircular canal detects the forward movement of the head such as nodding head up and down
Anterior Semicircular canal
The semicircular cancal detects the side to side movements such as shaking of head (e.g., shaking head no)
Lateral semicircular canal
Which semicircular canal detects head rotations such as tilting your head from shoulder to shoulder (e.g., cartwheel)
Posterior semicircular canal
This detects the acceleration
Utricle and saccule
This detects the acceleration vertically (e.g., free fall)
Saccule
This detects acceleration horizontally
Utricle
Inside the ampulla, there is a specialized sensory organ known as _______
Crista ampullaris
Macula is found in ____________ which detects accelerations (this is found at the membranous labyrinth)
Utricle and saccule
Ampullaris is found in ____________ which detects rotational movements (this is located at the osseus or bony labyrinth)
Semicircular canals
What is the cochlea?
It is the coiled snail shell, and starts at the cochlear base.
What is the function of the cochlea?
It sorts auditory components in terms of pitch and loudness. It also sorts temporal aspects of sounds.
It serves as energy transducer, meaning it converts mechanical energy into chemical energy
Which of the following is NOT the function of the cochlea?
A. Sorts auditory components in terms of pitch and loudness
B. Sorts temporal aspects of sounds
C. It is an energy transducer
D. Detects rotational movements
D.
This separates the scala vestibuli from the scala media
Reissner’s membrane
What is the importance of scala vestibuli?
The footplate is adjacent to the scala vestibuli
This is the sensory organ of hearing
Organ of corti
This separates the scala media from the scala tympani
Basilar membrane
This liquid flows inside the scala media
Endolymph
This liquid flows at scala vestibuli and scala tympani
Perilymph
Sodium is more concentrated here
Perilymph
Potassium is more concentrated here
Endolymph
Why are cochlear fluids important?
The difference of ionic concentration allows for a positive endocochlear potential and proper transduction of current along the hair cells
Describe the traveling wave
Tympanic membrane -> Oval window -> Scala vestibuli (Perilymph) -> Reissner’s Membrane -> Scala Media (Endolymph) -> Basilar membrane
The number of oscillations of the tympanic membrane -> footplate/sec is
Frequency
Describe the tonotopic arrangement
Higher frequency sounds is processed in the cochlear base, while lower frequency sounds are processed in the apex
True or False. If it is lower frequency, the travel is longer
True
Where are lower frequency sounds processed?
Apex
Traveling wave always travels from _____ to ______
From base to apex
Describe the basilar membrane at the apex
The basilar membrane is stiffer, thinner, and narrower at the base
than at the apex.
How many rows does the inner hair cells have?
1 Row from base -> Apex (3500)
How many rows do the outer hair cells have?
3 Rows from base -> 4 rows at apex (˜12000)
The tectorial membrane is in contact with what hair cell?
Outer hair cell
Movement of basilar membrane + tectorial membrane, what happens?
Shearing action which excites the outer hair cells
Excitation of the outer hair cells occurs primarily as a result of __________
Shearing effect on the cilia
Excitation of the inner hair cells is produced by _____________
It is produced by the effect of the fluid flow and turbulence of the endolymph
The Auditory Nerve is tonotopically arranged too.
High-intensity sounds are processed near the edges of the nerve
Low-intensity sounds are processed near the core of the nerve
Retrocochlear reflex
What kind of movement excites the inner hair cells?
Endolymphatic fluid movement
What neurotransmitter is released for energy conversion in hearing?
Glutamate
Where is the central auditory pathway located?
Brainstem
It is the first structure in the CAP (Central Auditory Pathway) to receive input via CN VIII and sends signals ipsilateral and contralateral. Junction to medulla and pons.
Cochlear nucleus
This is the first site of binaural interaction (between two ears). It receives information from both cochlear nuclei (ipsilater and contralateral side of the cochlear nuclei) as it specializes in sound localization.
SOC (Superior Olivary Complex)
How do we localize sounds?
Difference in time and intensity
This is located at the midbrain. It has input from both ipsilateral of superior olivary complex, and ipsilateral and contralateral of cochlear nucleus. Also communicates from the contralateral inferior colliculus (so the inferior colliculus communicates with one another).
Inferior colliculus
This is the final stop before going into the auditory cortex. Input is from the ipsilateral IC (inferior colliculus.)
Medial Geniculate Body
Sorting frequency and intensity components starts where?
Basilar membrane
The part of the malleus that is visible through the tympanic membrane is the
Manubrium
What structure found in the ear do not have protective/safety purposes?
Tunnel of Corti
True or false. The auditory labyrinth contain an osseus labyrinth without a membranous labyrinth.
False
True or False. The vestibular labyrinth contains an osseus labyrinth without a membranous labyrinth.
False
Which function of the ossicular chain provides the most intensity gain?
Decreasing area
The entrance to the external auditory meatus is the
Concha cava
A backflip will be detected by which semicircular canal?
Anterior Semicircular canal
The middle ear functions primarily as a(n)
a.) Resonator
b.) Impedance matcher
c.) Frequency and intensity analyzer
d.) Sensory organ for balance
Impedance matcher
If the outer hair cells primarily detect sound intensity, the inner hair cells are responsible of what?
Sound clarity
These parts of the auditory pathway involve decussation
Superior olivary complex and inferior colliculus
State the correct order of the auditory pathway
Cochlear nucleus -> SOC -> Inferior colliculus -> Medial geniculate body
The traveling wave theory postulates that cochlear response
Propagates from the basilar membrance from base to apex
What happens if there is no impedance matching?
Nothing will match the respective pressures of the cochlea and the outside envrionment
This part of the stapes is connected to the oval window
Footplate
The frequency analysis of the basilar membrane is dependent on
Stiffness, thickness, and width
Which of the following structures is a converter of energy?
a.) OHC
b.) TM (Tympanic Membrane)
c.) Oval window
d.) Auditroy Nerve
OHC
When a very loud sound is heard, muscles in the early may be activated. Which of the following muscles can be activated during this?
Tensor tympani
The incus is connected to the stapes via
Lenticular process
The retrocochlear pathway is tonotopically arrange. What does this entail?
Its border responds to higher frequency sounds, while its core responds to low frequency sounds
Decreasing area is between what?
Tympanic membrane and the oval window
Lever function happens through what?
The length difference between the manubrium (9mm) and the long process of the incus (7mm)
A racecar driver will primarily sense the forward movement of the car through their
Utricle
How do the cristae ampullaris detect movement?
It responds when the endolymph moves
The outer hair cells are separated from the inner hair cell row by the _______________
Tunnel of Corti
The ___________ is the upper boundary of the scala media, while the ________ forms the floor
Reissner’s membrane forms the upper boundary of the scala
media, and the basilar membrane forms the floor.
True or False. The inferior colliculus does not receive fibers of decussation.
False.
Rationale: Decussation means crossing of the nerve fiber from one side of the central nervous system. As such, the inferior colliculus receives input from the input from both ipsilateral (same side) and contralateral (opposite side) of the cochlear nucleus, and ipsilateral of of the superior olivary complex. It also communicates with the contralateral inferior colliculus.
What neurotransmitter is released to signal stimulate auditory nerve fibers?
Glutamate
True or False. The cochlea is both a spectrum analyzer and a transducer.
t
True or False. When the basilar membrane is displaced toward the scala vestibuli, the hair cells are activated, whereas when the basilar membrane is displaced toward the scala tympani, electrical activity of the hair cell is inhibited.
t
This is the primary brainstem location for localization of sound in space
Superior olivary complex
The ______________ of the brainstem is involved in both localization and intersensory interaction.
Inferior colliculus
The ____________ of the thalamus is the primary source of input to the core of the auditory cortex
Medical geniculate body
At the apex, the basilar membrane is wider or narrower than the base?
At the apex, the basilar membrane is wider than the base.
The _______ of the auditory cortex is responsible for primary reception of the auditory signal and is divided into three portions.
Core
The ______ region of the auditory cortex surrounds the core area for auditory reception.
Belt
