Auditory System B&B Flashcards
which of the inner ear bones pushes on the fluid-filled cochlea?
stapes - (smallest) pushes on fluid-filled cochlear, which stimulates hair cells in the Organ of Corti
[others are malleus and incus]
where do auditory nerve impulses go after being electrically converted in the inner ear (at the Organ of Corti)?
carried by cochlear nerve (CN VIII) to the cerebellopontine angle (in the lateral pons)
from there, connect to many structures including superior olivary nucleus, trapezoid body, lateral lemniscus, inferior colliculus, medial geniculate body, transverse temporal gyri of Heschl, etc
a brainstem lesion with hearing loss can most likely be located to where exactly?
cerebellopontine angle in the lateral pons - this is where auditory impulses are carried to by the cochlear nerve of CN VIII
which of the following is NOT an example of conductive hearing loss?
a. obstruction (wax)
b. otosclerosis
c. cochlear nerve failure
d. otitis media
c. cochlear nerve failure (acoustic neuroma) - this is sensorineural hearing loss
obstruction, otosclerosis (bony overgrowth of stapes), and otitis media are examples of conductive hearing loss - sound waves can’t be converted to nerves signals
presbycusis
age-related hearing loss due to degeneration of the Organ of Corti
slow developing sensorineural hearing loss
how does the Weber Test evaluate hearing?
place vibrating tuning fork on bridge of forehead, nose, or teeth
ask patient if they can hear the vibrations in both ears - should be equal on both sides
in CONDUCTIVE hearing loss, sound will be LOUDER in BAD ear because there is no background noise from the outside
in sensorineural hearing loss, sound will be quieter in bad ear because there is no CN VIII ability to sense vibration
[so you need to know which ear has hearing defect]
Your patient presents with complaint of hearing loss. You place a vibrating tuning fork on the bridge of their forehead and ask which side sounds louder. Your patient says it sounds louder on the L side. What type of hearing loss do they have?
a. conductive
b. sensorineural
(Weber Test)
trick question - you cannot tell without more information!!
in CONDUCTIVE hearing loss, sound will be LOUDER in BAD ear because there is no background noise from the outside
in sensorineural hearing loss, sound will be quieter in bad ear because there is no CN VIII ability to sense vibration
so you need to know which ear has hearing defect!!
how does the Rinne Test evaluate hearing?
place vibrating tuning fork first on mastoid bone (behind ear) to test bone conduction (BC) … wait until patient says they no longer hear it, then move tuning fork to just outside ear to test air conduction (AC) … ask if the patient can still hear
normal = they still hear, AC>BC
conductive hearing loss = patient cannot hear, BC>AC
sensorineural hearing loss = patient can still hear, but both AC and BC are reduced (but AC>BC)
what type of hearing loss is the Rinne Test best at detecting?
conductive loss
place vibrating tuning fork first on mastoid bone (behind ear) to test bone conduction (BC) … wait until patient says they no longer hear it, then move tuning fork to just outside ear to test air conduction (AC) … ask if the patient can still hear
normal = they still hear, AC>BC
conductive hearing loss = patient cannot hear, BC>AC
sensorineural hearing loss = patient can still hear, but both AC and BC are reduced (but AC>BC)
what becomes damaged in long-term noise exposure (musicians), and what type of sound is lost first?
damage to ciliated hair cells of Organ of Corti
high-frequency hearing is lost first (birds chirping)
within what portion of the temporal bone is the auditory and vestibular apparatus located?
petrous portion
the external ear (pinna + external ear canal) is derived from the ______ pharyngeal cleft
the auricle is derived from swellings/hillocks on the _____ pharyngeal arches
the tympanic membrane is derived from fusion of the ectoderm of the _____ pharyngeal cleft and the endoderm of the _____ pharyngeal pouch
the external ear (pinna + external ear canal) is derived from the FIRST pharyngeal CLEFT
the auricle is derived from swellings/hillocks on the FIRST and SECOND pharyngeal ARCHES
the tympanic membrane is derived from fusion of the ectoderm of the FIRST pharyngeal CLEFT and the endoderm of the FIRST pharyngeal POUCH
which ossicle (middle ear bone) is attached to the inner surface of the tympanic membrane?
malleus
[which attaches to incus, which attaches to stapes on the oval window of the inner ear]
what are the 2 skeletal muscles of the inner ear?
- tensor tympani: innervated by CN V3, attaches to malleus
- stapedius: innervated by CN VII, attaches to stapes
contracting reduces amplitude of vibration of the tympanic membrane and ossicles (response to loud sound to protect cochlear hair cells)
lesion of the CN ____ may causes hyperacusis, an increased perception of loudness because of the loss of the action of the stapedius.
lesion of the facial nerve (VII) may causes hyperacusis, an increased perception of loudness because of the loss of the action of the stapedius.
