Auditory system Flashcards
How is the ear divided?
Outer - pinna, external auditory canal
Middle - tympanic cavity, 3 bones; malleus, incus, stapes
Inner - cochlea, semicircular canals
3 function of outer ear
capture sound
amplify frequencies
protect ear from external threats
how does the outer ear amplify sounds?
by resonance
Function of middle ear?
Amplification
how is amplification of the middle ear achieved?
focusing vibrations from the tympanic membrane - LARGE SA
to the oval window
uses the ossciles
tympanic membrane projects onto malleus which projects onto incus which projects onto stapes ( which rests on the oval window)
use of incus -stapes joint increases the force on the oval window
simple answer of how amplification occurs in middle ear?
focusing of vibration from large SA to small SA - increases amplificationas pressure is increased
function of inner ear?
hearing via Cochlea
transduces vibration into nervous impulses
- frequency/ pitch and intensity analysis of sound occurs here
scala vestibuli contain?
perilymph- high in Na+
scala tympani contain?
perilymph- high in Na+
scala media contains?
Endolymph- high in K+
structures which contain perilymph in the inner ear are __ structures?This is high in sodium
bony structures
vestibuli, tympani
membranous structures like the _____ contain ______ high in K+
membranous structures like the SCALA MEDIA contain ENDOLYMPH- high in K+
basilar membrane arrangement
same principle as xylophone
narrow at base and wide and loose at apex
high frequency is sensitive at which part of basilar membrane?
BASE - narrow andtight
low frequency is detected at what part of basilar membrane?
apex
loose and wide
where is the tectorial membrane ?
Inner ear
Organ of Corti
above the hair cells
only outer hair cells are in contact with tectorial membrane
___ carry 95% of afferent information of the auditory nerve.
inner hair cells carry 95% of afferent information of the auditory nerve.
efferent information of auditory nerve is via __
efferent information of auditory nerve is via OUTER HAIR CELL
hearing acuity test
pure tone audiometry
PTA
TYMPANOMETRY
Examination used to test the condition of the middle ear and mobility of the eardrum (tympanic membrane) and the conduction bones by creating variations of air pressure in the ear canal.
common result of tympanometry
B
Middle ear effusion
Perforation of tympanic membrane
Eustachian (pharyngotympanic) tube dysfunction
Occluded ear canal
newborn hearing screening test
otoacoustic emissions
normal cochlea produces these sounds
low intensity sound
outer hair cells as they expand and contract
Conductive hearing loss
Problem is located in outer or middle ear.
Sensorineural hearing loss
Problem is located in the inner ear or the auditory nerve.
