Auditory and Vestibular systems

What is the main role of the outer ear?

To collect and direct sound into the middle ear.

Why is it difficult to distinguish sounds on the telephone?

They have difficulties transmitting full range of frequencies

Stapedius muscle

Innervated by facial nerve

What is Darwin's tubercle?

A genetically determined feature present in some individuals' ears.

At what age do the external acoustic meatus and pinna reach adult size?

By age 9-12 years.

What is the tympanic membrane commonly known as?

The eardrum.

What does a 'dull' tympanic membrane indicate?

That the 'cone of light' cannot be seen, often due to infection, pressure changes, or fluid buildup.

What are the three bones of oscillation in the middle ear?

Malleus, Incus, and Stapes.

What is the function of the bones of oscillation?

Transform the acoustic pressure waves that hit the TM into mechanical energy

What bone attaches to the tympanic membrane

Malleus

What is the function of the Eustachian tube?

To equalize air pressure in the middle ear to atmospheric pressure in the ear canal.

Where is the eustachian tube located?

Tube between the middle ear and the posterior nasopharynx, surrounded by adenoids

The eustachian tube opens via actions of...

The levator veli palatini, and tensor veli palatani

How does the middle ear transform sound?

By boosting vibrations to prevent sound energy loss when transferring from air to fluid.

1. Area ratio advantage

2. Curved membrane buckling

3. Level action

What is the area ratio advantage in the middle ear?

The tympanic membrane is larger than the oval window, concentrating sound waves and increasing pressure by approximately 17 times.

What is the significance of the curved membrane buckling in sound transformation?

The tympanic membrane vibrates in segments, allowing multiple segments to move at once.

What role do the malleus and incus play in sound transformation?

They act like a lever, increasing force and adding a 2dB boost when the eardrum moves.

What are the three parts of the inner ear?

Cochlea of the auditory system, vestibule of the vestibular system, and semicircle canals of the vestibular system

What is the size of the stapes?

It is the smallest bone in the body, measuring 3.5mm.

What happens during the sequential movement of the bones in the middle ear?

Acoustic pressure waves are transformed into mechanical energy, creating hydraulic pressure waves within the cochlea.

How does the Eustachian tube's orientation differ in children compared to adults?

It is more narrow and horizontal in children, making it easier for fluid to accumulate.

What is the significance of the tympanic membrane's mobility?

It is mobile yet sturdy, allowing it to effectively transmit sound vibrations.

What is the function of the round window in the middle ear?

It allows for the release of pressure in the cochlea as sound waves travel through.

What is the primary function of the vestibular system?

Maintain balance, keep the body upright, and understand spatial orientation.

What structures make up the vestibular system?

Semicircular canals and otolith organs (utricle and saccule).

What do semicircular canals detect?

Rotational movements of the head.

What do otolith organs (utricle and saccule) detect?

Linear movements (forward/backward, up/down) and gravity.

How does the vestibular system convert movement into nerve signals?

Movement of fluid within the canals compresses hair cells (on the organ of corti) , which then transfer the movement into nerve signals.

What is the role of the vestibular nerve?

Carry signals from the vestibular system to the brainstem and cerebellum.

What is the cochlea?

A bony coiled structure in the inner ear.

What are the three channels of the cochlea?

Scala vestibuli, scala media, and scala tympani.

What fluid is contained in the scala media?

Endolymph.

What is the scala vestibuli?

One channel of the cochlea: base at oval window, runs up the apex, and contains perilymph

What is the scala tympani?

One channel of the cochlea: base at round window, runs down from the apex, and contains perilymph

What happens when the basilar membrane vibrates?

Hair cells on the organ of corti move against the tectorial membrane, converting sound waves into electrical nerve impulses.

Where is the organ of corti?

On the surface of the basilar membrane

What happens in the cochlea?

Movement of the perilymph in the scala vestibuli causes the vestibular membrane to vibrate, this vibration is transmitted through the endolymph to move the basilar membrane.

What is an audiogram?

A test that measures hearing ability, showing frequency (pitch) on the horizontal axis and hearing level (loudness) on the vertical axis.

What are the symbols for left and right ear on an audiogram?

X= left, O=Right

What does air conduction testing show?

Total hearing loss.

What does bone conduction testing indicate?

Inner ear hearing loss as it bypasses the outer and middle ear.

What is conductive hearing loss?

A problem with the mechanics of the outer and/or middle ear.

What is sensorineural hearing loss?

A problem with the inner ear.

What is the 'Speech Banana' on an audiogram?

Shows the phonemes that typically appear on an audiogram, indicating where speech sounds fall in terms of frequency and loudness.

What is otitis media?

Inflammation of the lining of the middle ear, often due to infections and blockage of the eustachian tube.

What is adhesive otitis media/ otitis media with effusion?

Glue ear: Fluid in the middle ear behind the tympanic membrane, which affects movement of TM

What type of hearing loss can otitis media cause?

Conductive hearing loss

Why is otitis media more common in children?

Their eustachian tubes are smaller and more horizontal

How to treat Otitis Media?

Surgical removal of adenoids, myringotomy (removal of fluid), grommets

What do grommets do?

Equalise pressure

What is presbycusis?

Gradual hearing disorder due to aging, characterised by degeneration across outer, middle and inner ear, as well as cranial nerve.

What is noise-induced hearing loss?

Can be gradual or sudden, often resulting from exposure to loud sounds and leading to damage of hair cells.

What is an acoustic neuroma?

A benign brain tumour that affects the schwann cells that form the myelin sheath of the vestibulocochlear nerve.

What are the symptoms of an acoustic neuroma?

Unilateral (1 sided) hearing loss, tinnitus and balance problems

How do hearing aids function?

Convert sound signals into electrical signals and amplify sound as necessary.

What type of hearing loss are hearing aids good for?

Sensorineural

What is a cochlear implant?

A device for severe to profound hearing loss that converts sound into electrical signals sent directly to the auditory nerve.

What type of hearing loss are cochlear implants used for?

Profound hearing loss (when cochlea is damaged)

What is a BAHA?

Used for conductive or mixed hearing loss, transmitting sound directly to the cochlea.

What device would be used for profound hearing loss

Cochlear implant

What is tympanometry?

Measures the mobility of the tympanic membrane (eardrum).

What structure converts sound vibrations into electrical signals?

Organ of corti

What are adenoids also known as?

Pharyngeal tonsils

The stapes connects to the inner ear at

The oval window

What is the purpose of otoacoustic emissions (OAE) testing?

Measures cochlear hair cell function and is often used in newborn hearing screenings.

What is noise induced hearing loss?

Hearing loss of the inner ear

Can be gradual or after exposure to sudden noise

Tinnitus is often the first sign

Caused by damage and eventual death of hair cells