Flashcards in Auditory physiology Deck (26):
What constitutes the outer ear?
Pinna, auditory canal and tympanic membrane.
What is the purpose of the outer ear?
To transmit sound waves via vibration of eardrum
What constitutes the middle ear?
Air-filled space with three bones called the ossicles.
What are the ossicles?
Malleus, incus, stapes.
What is the purpose of the middle ear?
Conduct and amplify sound from tympanic membrane to inner ear
What causes ossicles to move? Which bones are where?
Back and forth movement of the tympanic membrane from sound waves. Malleus in contact with TM, then incus, then staples in contact w/ oval window.
What constitutes the inner ear?
Snail-shaped, fluid filled cochlea.
What are the three chambers of the cochlea?
Scala vestibuli (perilymph) (upper)
Scala media (endolymph) (middle)
Scala tympani (perilymph) (lower)
What is the difference between perilymph and endolymph?
Ion concentrations! Endolymph is filtrate of CSF. Gets secreted via endolymphatic duct and is slowly absorbed by scala media cells, creating slow turnover. Perilymph also experiences slow turnover. Voltage potential between endolymph and and perilymph = +80mV in scala media.
What is the role of the scala vestibuli?
Incoming portion of vibrations from footplate (stapes via oval window).
What is the role of the scala media?
Hair cells of organ of corti located in scala media; sound waves vibrate the basilar membrane, vibration is transduced by specialized hair cells.
How are vibrations conducted through the inner ear?
Movement of the stapes footplate produces pressure waves in the fluids of the inner ear, and these cause a deflection of the basilar membrane, which in turn deflects the hair bundle. Basilar membrane moves up and down, which leads to a deflection of the stereocilia outward and inward, thus opening and closing the transduction channels via the tip links. This communicates to auditory nerves --> brain stem.
What is tonotopy?
Each frequency leads to vibration at specific location on basilar membrane.
Where are low frequency sounds heard best?
Apex, which is wide and flexible. (Near helicotrema)
Where are high frequency sounds heard best?
Base of cochlea, which is thin and rigid.
What are the labyrinths?
Set of channels carved into the temporal bone during development, contains vestibular (dorsal) segment and cochlear (ventral) segment.
What is conductive hearing loss?
Due to blocked conduction of sound.
What will be Rinne test show with conductive hearing loss?
Will be abnormal - louder hearing at bone than air. (because air pathway is blocked).
What will Weber test findings be with conductive hearing loss?
Louder in the affected ear. (Like covering ear w/ hand)
What is sensorineural hearing loss?
Hearing loss caused by nerve damage.
What does the rinne test show w/ sensorineural hearing loss?
What does the weber test show with sensorineural hearing loss?
Louder in the unaffected ear.
What is the pathogenesis of noise-induced hearing loss?
Damage to steriociliated cells in the organ of Corti. Loss of high frequency hearing 1st.
How can suddenly extremely loud noises produce heairng loss?
Rupture of tympanic membrane.
What it is called when there is overgrowth of desquamated keratin cells in the middle ear space?