audiology Flashcards
what is the resonant frequency of the ear canal
2500 Hz
what frequency of sounds does the tympanic membrane respond to
low
what bones are in the ossicular chain
- malleus which is embedded in the tympanic membrane
- incus which is connected in a tight joint that permits little movement
- stapes which inserts into the oval window
what is the amplification of sound by the ossicular chain
30 dB
which muscles dampen vibrations of the tympanic membrane
- tensor timpani: innervated by V and is the smallest muscle in the body
- stapedius muscle which stiffens the chain to reduce vibrations
what is the acoustic reflex
the tympanic membrane stiffens toprotect the ears
what is the function of the eustachian tube
- maintains equal air pressure in middle ear
how does the eustachian tube function
- tensor veli palatini aids in opening
what is the oval window
small opening in the temporal bone that houses the inner ear
what are the labyrinths or tunnels in the inner ear filled with
a fluid called perilymph
what are the major structures in the inner ear
- vestibular system
2. cochlea
what fluid fills the cochlea
endolymph
what ies on the floor of the cochlear duct that transmits sound
basilar membrane which contains the organ of corti
what are the hair cells called
cilia
how is sound transmitted through the cochlea
- vibrations from the footplate of the stapes create wave movements in the perilymph
- through REissners membrane, the movements are transmitted to the endolymph which transmits movement to the basilar membrane
- at the tip or apex the membrane is thicker, wider and more lax than the base
- low frequency sounds stimulate the apex and high frequency stimulate the base
- the cilia respond to the vibrations and are sheared. This turns the energy into electric which stimulates nerve endings
where do the auditory nerve fibers exit the inner ear
internal auditory meatus
what does hertz mean
cycles per second. 200 Hz means 200 cycles per second
what is the normal sound pressure level of speech
50-70 dB
what is the pain threshold for sound pressure
140 dB
what is the hearing level
lowest intensity of a sound necessary to stimulate the auditory system. THe hearing level is the audiometric zero
the human air is most sensitive to sounds in what frequency range
100-4000 Hz
at what age can a baby turn its head towards sound`
3 to 4 months
what factors increase a child at risk for hearing loss
- malformation of the head and neck
- maternal history of drugs or alcohol abuse
- maternal diseases (rubella, syphilis) during pregnancy
- genetics
what are the degrees of hearing loss
16 to 25 dB HL: slight 26-40 dB HL: mild 41-55: moderately 56-70: moderately severe 71-90: severe
why is conductive hearing loss never profound
there is always some hearing left because of bone conduction
what are the causes of conductive hearing loss
- abnormalities of the external auditory canal, tympanic membrane, or ossicular chain
- birth defects, diseases, and foreign bodies
- aural atresia, microtia, stenosis
- external otitis: infection of the skin of external auditory canal
- foreign objects in the ear canal and bony growths
- otitis media
- otosclerosis
- otospongiosis
- ossicular disconuity
what is aural atresia
where the external ear canal is completely closed
what is microtia
small pinna
what are the characteristics of otitis media
- creates a conductive loss of 20-35 dB HL which often goes undetected in pure tone screens which are carrie out at 25 dB HL
- serous otitis media: the middle ear is inflamed and filled with fluid. The Eustachian tube is blocked so fresh air does not ventilate. The middle ear becomes airtight. Increased air pressure out side the middle ear pushes the tympanic membrane inward reducing mobility
- acute otitis media: sudden onset due to infection. Quick build up of fluid causing pain. Child has fever. May cause the tympanic membrane to rupture. treated by myringtomy where a small incision in tympanic membrane relieves pressure
- chronic otitis media: from permanent damage to middle ear structures due to erosion of ossicles, cholosteotoma, atrophy or perforation of tympanic membrane
what is otosclerosis
spongy growth starts on the footplate and they become rigid so the stapes does not move into the oval window
what is Carhart’s notch
pattern of bone conduction thresholds characterized by reduced bone-conduction sensitivity at 2000 Hz
what is otospongiosis
disease that causes the stapes to become too soft to vitrate. The stapes is surgically removed by stapedectomy and a prothesis is inserted