Case 4 - How we do it and what goes wrong Flashcards
what does 0dB mean
does not mean no sound at all it just means sound pressure level
what is frequency measured in and what is normal
measured in Hz
- 20-20000Hz is normal
what is speech in Hz
200-500Hz
size of the external ear canal
one inch tube with 7mm diameter
how much does sound increase by when going down the external ear canal
10-20dB
what is the main function of the external ear
to protect the delicate ear drum but as with any hole it can collect debris and moisture which would encourage bacteria growth
how does ear canal skin grow
seems to migrate, grow like fingernails so ear canal is almost like a converyor belt
what type of wax do caucasians and black people have
honey wax
what kind of wax do asians have
flaky wax
what is the universal quality of wax
it is waterproof
how is the middle ear ventilated
at atmospheric pressure: physiological gas exchange across the mucosa
at abnormal pressure: eustachian tube opening - in emergency to prevent out ears from busting
air:
low pressure high-displacement vibration
cochlear fluids:
high pressure low-displacement vibration
what starts the vibrations of the occicles
the malleus
how long is the malleus handle
longer than the incus long process
what is the tympanic membrane
a mechanical level
what happens when there is stiffening of the ossicles
makes us more deaf nd protecting the inner ear from noise damage
how long can we tense for
40 minutes
how is the stapedius stimulated
acoustically.
what happens when sound reaches the oval window
it vibrates and sets up a wave in the perilymph fluid
where does this fluid go
travels the two and a half turns of the cochlear and washes up on the round window
what did Kemp find
that the outer hair cells were in fact a muscular function, not for hearing
when the basilar membrane vibrated with sound, the outer hair cell muscles would tense the tectorial membrane and this would focus the resonant frequency of the basal membrane so that you could hear the difference between smaller changes in frequency
if the cochlea was poisoned, in other words if the outer hair cells died, then the cochlea could only sense a change in 50Hz frequency
what is the rigid resonating structure made form
the basilar membrane, the tectorial membrane and oCHs
what do IHCs sense
orignal sense of sound and depolarise when the hair moves to angstroms In fluid movement inside the organ od corti.
when would fine tuning be removed
OHC death
what does conductive hearing impairment involve
the external and middle ear while conduct sound to the cochlea
what does sensorineural impairment involve
the sensation of hearing sound in the cochlea and the associated nerve pathway to the brain
what infection makes the external ear hot and inflamed
perichondritis makes the ear hot and inflamed and is usually due to pseudomonas aeruginosa and as soon as the external ear canal is cut off conductive hearing impairment will result.
if you have a perforation of the tympanic membrane, this will cause a conductive hearing impairment
what would fluid behind the eardrum cause
conductive impairment
percentage of children who recover after 3 months having grommets
50%
what do the other 50% have
- hearing loss
- speech delay
- educational impairment
what can conductive hearing impairment also be caused by
abnormalities of the ossicles
- severe head injury
- eroded away in infection
- otosclerosis
what is the most well known cause of neurosensory hearing loss
acoustic neuroma which is a benign tumour on the cochlear nerve
