Aural Anaphysio Flashcards by Jenneth Karylle Barba

What is the main function of the outer ear?

Sound funnel
Resonation

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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)

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What is the concha?

It is the entrance to the ear canal
Shell

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How long is the external auditory meatus?

7 mm diameter
2.5 cm long, + 1.5 cm from tragus

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What is the external auditory meatus made of?

lateral 1/3: cartilage
Medial 2/3: osseous-bony structure (temporal bone)

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This selectively enhances sound

outer ear

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What is the range where it is enhanced by outer ear?

sounds that are 1500 - 8000 Hz

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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.

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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.

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This bone in the middle ear is called the anvil. What is the name of this bone?

Incus

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This is the border between the outer ear and middle ear

tympanic membrane

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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

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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.

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This is the soft part of the tympanic membrane

Pars flaccida

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What is the area of the tympanic membrane

55 m^2

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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

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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).

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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.

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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.

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This provides a connection to the middle ear and inner ear

Footplate of the stapes

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True or False. The footplate is the same size as the oval window

True (3.5 mm^2)

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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.

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What is the least impedance matching?

Lever difference (2 dB)

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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.

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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

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.

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.

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