Auditory System Flashcards
is the outer inner or middle ear air filled? water filled?
outer and middle ear are air filled
inner ear is water filled
what are the components of the external ear and what does it mainly do?
auricle, external auditory meatus and the tympanic membrane
the external ear collects and transmits sounds
what is the main purpose of the tympanic membrane?
transform sound waves to mechanical vibrations
what are the three parts/layers of the tympanic membrane?
- skin of the external auditory meatus
- connective tissue with a core of radially and circularly arranged collagen fibers
- mucous membrane of the middle ear
what are the components of the middle ear and what is its main purpse?
- malleus
- incus
- stapes
- middle ear cavity
- oval and round window
- tensor tympani muscle and stapedius muscle
transmit and amplify sound signals
what is the main purpose of the tensor tympani and stapedius muscles?
attenuation of sound transmission
what are the components of the inner ear and what is its main purpose?
- scala vestibuli
- scala tympani
- cochlear duct and scala media
transformed sound to electrical signal
what is at the center of the boney cochlea and what does it contain?
boney modiolus
perikarya of the spiral ganglion
what is in the center of each turn of the cochlea and what does it seperate?
the membraneous cochlear duct (scala media)
which separates the scala vestibuli and the scala tympani
how do you know you are a the apex of the cochlea?
the membraneous cochlear duct ends blindly
the scala vestibuli and scala tympani become continuous at the helicotrema
what does the organ of corti do and where is it located?
rests on the basilar membrane and protects the scala media
hair cells are supported by what and what do they do?
phalangeal (supportive) cells that help stiffen the superior surface of the organ of corti
the one inner hair cell is innervated by how many spiral ganglions? 10 outer hair cells?
20 spiral ganglion neurons
1 spiral ganglion neurons
what is happening if there is no stimulation of a hair cell?
- stereocilia are deflected away from the longer stereocilia
- hair cell membrane hyperpolarizes
- afferent nerve fibers of spiral ganglion neurons are not stimulated
what happens during stimulation of a hair cell?
- stereocilia are deflected towards the longer stereocilia
- influx of K+ ions
- depolarization of the hair cell membrane
- influx of Ca2+ ions
- neurotransmitters are released
- afferent nerve fibers of spiral ganglion neurons are stimulated
the tonotopic localization in the organ of corti provides what?
the ability to tell where sounds are coming from
i.e. higher frequencies are detected near the middle ear
lower tones are detected closer to the helicotrema
briefly explain the auditory pathway
cochlea —> cochlear nerve —-> cochlear nuclei in medulla junction—-> crosses over to the superior olivary nucleus in pons (lateral lemniscus) ——> inferior colliculus of midbrain (synapse occurs here) —–> medial geniculate nucleus in the thalmus —–> transverse temporal gyrus (primary auditory cortex)
a unilateral lesion to the nerve or cochlear nuclei can cause what?
hearing loss - ipsilateral ear
*** does not cause deafness because there are bilateral projections at multiple sites in thee brainstem
what types of sound information are transmitted to our brain?
tone- high and low frequency
amplitude of sound- loud or quite (differential firing of afferent fibers)
sound localization- superior olivary nucleus, trapezoid body
what fibers and nuclei allow us to regulate selective attention to certain sounds?
superior olivary nuclei and olivocochlear efferent fibers to inhibit outer hair cells
what is conductive hearing loss?
occurs only in the outer and middle ear due to
- foreign bodies in the external auditory meatus
- perforated tympanic membrane
- otitis media
- otosclerosis ( overgrowth of bones around stapes)
- cholesteatoma (overgrowth of keratin debris within middle ear cavity)
what is sensory neural hearing loss?
congenital hearing loss due to genetic mutations or developmental insults (acquired hearing loss)
- noisy induced hearing loss ( damage to stereociliated cells in organ of corti, loss of high frequency hearing first)
- aging related progressive bilateral/symmetric sensorineural hearing loss (hearing loss of higher frequencies due to destruction of hair cells at the cochlear base
- lesion in the auditory pathway
what are the three auditory tests?
whisper, rinne and weber tests
what is bone conduction (rinne)?
sound vibration can be transmitted through temporal bone vibration to inner ear
less effective than air conduction
what is air conduction (rinne)?
sound transmission through tympanic membrane vibration and ossicle movement
more effective than bone conduction
what are the findings for the rinne test?
with conductive hearing loss you can hear bone conduction more clearly than air conduction which is not normal
with sensory neural hearing loss you can hear air conduction more clearly than bone conduction
what are the findings of the weber test?
with conductive hearing loss the affected ear will hear the tuning fork louder
with sensory neural hearing loss the sounds are heard better in the unaffected ear
