HEARING Flashcards
what are the 2 theories of language development?
Poverty of stimulus theory (based on Chomsky’s Nativist theory)
Empiricist theory
what is neural plasticity?
the inherent ability of the auditory system to reorganise its functioning an early age
how is neural plasticity related to age? How is this important in the context of hearing loss?
If congenital hearing loss is corrected by the age of 3, recovery is possible. Much after this, the functionality hearing capabilities will be lost forever
which lemniscus (lateral or medial) does the auditory pathway run through?
LATERAL lemniscus
what is unique about the organisation of the primary auditory cortex?
tonotopically arranged, meaning it is ordered in terms of frequency recognition
what is the innervation of the levator veli palatini?
pharyngeal branch of vagus nerve
what is the innervation of the tensor veli palatini?
mandibular branch of trigeminal
where is perilymph found?
bony labyrinth
where is endolymph found?
membranous labyrinth
scala tympani and scala vestibuli are ducts within which cochlear structure?
bony labyrinth
which cochlear duct does the stapes bone communicate with at the oval window?
Scala vestibuli
what is the name of the membrane that seperates the scala vestibuli and scala media?
vestibular membrane
what is the name of the membrane that seperates the scala media and scala tympani?
basillar membrane
what is the function of the tectorial membrane?
provides a surface upon which K+ rich endolymph runs over hair cells in response to sound frequencies
what is the absolute hearing range of humans?
20-20000Hz
what is the sensitive hearing range of humans?
1500-4000Hz
short / high frequency waves are absorbed in which part of the cochlear duct?
Base of cochlear
low / low frequency waves are absorbed in which part of the cochlear duct?
apex/helicotrema
what is the function of inner hair cells?
5-10% of all hair cells
important in conveying sound into action potentials
what is the function of outer hair cells?
90-95% of all hair cells
involved in sound modulation in response to sensory input
where is the organ of corti located?
scala media of cochlear duct
the scala vestibuli and scala tympani belong to which cochlear labyrinth?
Bony labyrinth
how is sound transmitted through bone (as opposed to air)?
bone conduction vibrates skull against cochlear, which in turn vibrates basillar membrane of scala media
what are deiters cells?
supporting cells that separate and support the IHC and OHC
what is the tectorial membrane?
membrane overlying the IHC of scala media
tip-link proteins open K+ channels on stereocilia of IHC, what occurs after this?
K+ influx and IHC depolarisation
Ca2+ influx
Glutamate release
type I spiral ganglion neurone excitation
how do outer hair cells modulate sound
cause hair cell elongation in response to efferent stimulation
More space between tectorial membrane and stereocilia means less endolymph flow
what are the two main components of the vestibular system?
vestibule (containing otholitic organs)
semicircular canals
what is the function of the vestibule?
detects linear changes in direction (eg. accelleration)
the utricle detects ……… changes in accelleration
horizontal
the saccule detects ……… changes in accelleration
vertical
what is the function of macullae?
receptor cells that convey information from hair cells of utricle/saccule to the vestibular nerve
what is the otoconia analogous to in the cochlear?
tectorial membrane
what type of movement do the semicircular canals sense?
dynamic and angular movement
what is the crista ampullaris?
sensory organ of rotation, found in the ampulla of each of the semicircular canals
cone shaped structure containing hair cells that are moved by the cupulla in response to angular changes in accelleration
describe the vestibo-ocular reflex
detects angular movement to either side and contracts extraocular muscles to move the other way
what ganglion is associated with the vestibo-ocular relfex?
scarpa’s ganglion
what is nystagmus?
involuntary eye movement that occurs when semicircular canals are being stimulated when the head is not in motion
what descending motor tract receives input from the vestibular nuclei in order to control core muscle tone?
vestibulo-spinal
what is the diagnostic significance of outer hair cells?
they are motile, releasing otoacoustic emissions which can be measured in a hearing loss diagnostic test
what physical property of the basillar membrane allows it to absorb different frequencies?
Tighter @ cochlear base, meaning higher frequencies absorbed here
what is pure tone audiometry?
hearing levels (in Db) on y axis and frequency on x axis
tests bone and air conduction at different frequencies
what are otoacoustic emmsions tests?
how can they be interpreted?
measurement of low intensity signals released by outer hair cells of inner ear.
OAE normal - conductive hearing loss
OAE reduced significantly - cochlear deafness
OAE normal/slightly low - auditory pathway neuropathy
what is tympanometry?
used to test mobility of tympanic membrane and auditory ossicles
how is conductive hearing loss recognised on a pure tone audiogram?
when a net difference of 10Db or more is seen between bone and air conduction
how is sensorineural loss recognised on a pure tone audiogram?
when there is a marked reduction in bone and air conduction at certain frequencies
how is mixed hearing loss identified on a pure tone audiogram?
no pattern
