Auditory System Flashcards
Ear is divided into what sections?
outer
middle
inner
Where is the ear located?
embedded in the petrous portion of the temporal bone
List functions of the outer ear.
capture sound (focus on tympanic membrane) amplify some frequencies (resonance in the canal) protect ear from external threat
What is the function of the middle ear?
amplification (typanic membrane > oval window) due to decrease in SA, uses leverage from incustapes joint to ^ force
Hearing part of the inner ear is?
cochlea
Function of the cochlea?
transduction of vibration into nervous impulses
produces frequency and intensity analysis
what are the three compartments of the cochlea?
scala vestibuli
scala tympani
scala media
What are the scala tympani and scala vestibuli?
Bony structures, contain perilymph (high in sodium)
What is the scala media?
Membranous structure, contains endolymph (high in potassium).
What important organ is located in the scala media?
hearing organ or Organ of Corti
Organ of Corti lies in what structure?
basilar membrane
How is the basilar membrane organised?
tonotopically (basically like a xylophone, sensitive to different frequencies along its length)
Organ of Corti contains what hair cell types?
inner hair cells
outer hair cells
How are inner hair cells arranged?
on one column
How are outer hair cells arranged?
on three columns
What is located above the hair cells?
tectorial membrane
What does the tectorial membrane do?
allows hair deflection which in turn depolarises the cell
Which hair cell type is in contact with the tectorial membrane?
outer hair cell
What information does the inner hair cell carry?
95% of the afferent information of the auditory nerve
What is the function of the IHC?
transduction of the sound into nerve impulses
What information does the OHC carry?
95% of the efferent information of the auditory nerve
What is the function of the OHC?
modulation of the sensitivity of the response
Hairs of the hair cells are called?
stereocilia
Deflection of the stereocilia towards the cilium will do what?
open K+ channels
The opening of K+ channels leads to what?
depolarises the cell and neurotransmitter is liberated
Higher amplitudes of sound will cause a greater or lesser deflection of streocilia?
greater
Depolarisation of the cell opens or closes K+ channels?
opens K+ channels
Spiral ganglions from each cochlea project via which nerve?
auditory vestibular nerve (VIII)
Do the spiral ganglions project to the contralateral or ipsilateral cochlear nuclei?
ipsilateral
Auditory information crosses at what level?
superior olive level
After the crossing, all connections become?
bilateral
Define frequency/pitch. What are the units?
cycles per second, perceived tone
Hz
Define amplitude/loudness. What are the units?
sound pressure, subjective attribute correlated with physical strength
dB
What is the human range of hearing?
Frequency: 20–20,000Hz
Loudness: 0 dB to 120 dB
How does hearing acuity change with age?
decreases with age, particularly higher frequencies
What are the aims of a hearing assessment?
answer the qs: is there a hearing loss, what degree, what type?
What procedures can be used during a hearing assessment?
tunning fork, audiometry, central processing, tympanometry, otoacustic emission, electrocochleography, evoked potentials
What is a tunning fork used for?
used to establish the probable presence or absence of a hearing loss with a significant conductive component
What is pure tone audiometry?
science of measuring hearing acuity for variations in sound intensity and frequency
What is an audiogram?
where the hearing thresholds are plotted to define if there is a hearing loss or not
What is tympanometry?
Exam used to test condition of middle ear + mobility of eardrum and conduction bones by creating variations of air pressure in ear canal
What are the most common results of tympanometry?
A: normal, B: -ve middle ear pressure, C: middle ear effusion, eardrum perforation, eustachian tube dysfunction, occluded ear canal
The normal cochlea produces?
produces low-intensity sounds called OAE
OAEs are produced by?
OHC
OAEs are a part of what screening/testing?
newborn hearing screening
hearing loss monitoring
What is auditory brainstem response?
alterations in the latency of waves can point to the location of the deficit
ABR commonly used in what population and why?
babies and children
does not require patients attention
Cortical potentials could be affected in?
neurological conditions
processing problems
List types of hearing loss.
conductive
sensorineural
mixed hearing loss
Where is the problem located in conductive hearing loss?
outer or middle ear
Where is the problem located in sensorineural hearing loss?
inner ear or the auditory nerve
Where is the problem located in mixed hearing loss?
conduction and transduction of sound are affected, problem affects more than one part of the ear
How can the degree of hearing loss be classified?
mild
moderate
severe
profound
List causes of conductive hearing loss in the outer ear.
wax
foreign body
List causes of conductive hearing loss in the middle ear.
otitis
otosclerosis
List causes of sensorineural hearing loss in the inner ear.
presbycusis
ototoxicity
List causes of sensorineural hearing loss in the nerve.
VIII nerve tumour
What are treatments options for hearing loss?
treat underlying cause
hearing aids
cochlear implants
brainstem implants
What does a cochlear implant need to function?
functional auditory nerve
How does a cochlear implant work?
replaces the function of the hair cells
Who is a brainstem implant advised for?
those with bilateral auditory nerve damage
