Hearing and Balance Flashcards
What are the three parts of the ear
outer ear
middle ear
inner ear
What is in the outer ear and what does it do
it contains the external part and ear canal
carries sound waves throughout the ear canal .
external part collects sounds waves and directs them to the tympanic membrane through external auditory canal
what is in the middle ear and what does it do
where does it extend from
tympanic membrane and malleus, incus, stapes
Sound waves are conducted through the middle ear
extends from tympanic membrane to oval window. Conducts sound waves over the bones
What is in the inner ear and what does it do
cochlear – mechanical vibrations converted into soundwaves
made up of fluid spaces, membrane structures and hair cells - gated ion channels
what separates the internal and external ear
tympanic membrane
3 fluids in the cochlea
scala vestibuli
scala tympani
scala media
Which two fluids contain perilymph> which is like extracellular fluid
scala vestibuli
scale tympani
Scala media contains endolymph, what ion is it high in?
potassium so there is an electrochemical gradient between it and the fluid on the outside of the membrane
The electrochemical gradient between the endolymph in SM and ICF in what is important for hearing
Hair cells
The basilar membrane which is at the base of the organ of corti, which contains sensory receptors, when it moves what does it cause
deplarisation of hair cell in organ of corti
what is the function of the tectorial membrane
transforms sounds into mechanical stimuli
What are the finger like projections that sit on hair cells in the endolymph between organ of corti and the tympanic membrane
stereocilia
Stereocilia are joined by tip links which also attach to what
gated potassium ion channels
How is an AP created in hearing
waves of vibration of fluid membranes make hair cells bend causing movement of ions so Ap generated
when stereo cilia move tip links stretch opening potassium channels this opens calcium channels and neurotransmitter released
what nerve does the Ap go down
vestibulocochlear nerve
How is potassium recycled back into the endolymph
Potassium is recycled back into the endolymph via the stria vascularis
High frequency sounds vibrate at start of cochlea and low at the end/apex . What is sound measured in
Decibels – logarithmic scale
10x log10 sound 1/sound 2
What is the acoustic reflex- dampen sound
does it fatigue easily after prolonged and sudden noise
Acoustic reflex – stapedius muscle – draws the stapes away form the oval window
contraction in response to loud noise
however fatigues easily and quickly after purloined or sudden noise
What is the mechanism of damage from noise
damage to what
what reaction is caused
damage to hair cells/cilia
inflammation
excitotoxicity - neurones damaged by over activation of receptors from excitatory neuroTgltuamate such as NMDA
What two ways can hearing be classified as lost
conductive
sensorineural
what is conductive hearing loss
outer/middle ear – wax build up/infection
what is sensorineural hearing loss
inner ear/brain such as damage to hair cells and nerves
what are the two tests to tell type of hearing loss
Rinne test
webers test
what is rines test
what instrument is used
acoustic fork – place next to ear and on bone
conductive hearing loss
- - normal – air louder
- conductive – bone louder
- Sensorineural – air louder
