audio-exam 1 Flashcards
prevalence HL
In U.S., ≈ 10% with hearing loss ≈ 26 million hard-of-hearing (HOH) Hearing loss makes communication difficult since speech is primary means of communication ≈ 2 million “deaf” individuals Severe-to-profound bilateral hearing loss Prevalence increases with age 17 in 1000 children under age 18 40 – 50% ≥ 75 years
audiology vs otology
audiology- ear aids life
otology- life risked by ear?
audiology specialties- PRIME
medical- evals, ototoxic monitoring, screenings
rehab- hearing aids, AR
pediatric- minimize effect, special kid/parent skills
educational- screen, eval, collab w teachers/SLP, rehab, consult (rm acoustics)
industrial- prevent HL by reducing, educating, protective etc
peripheral vs central auditory
peripheral: outer =>middle => inner => cranial nerve 8
central- Cochlear nucleus in brainstem to auditory cortex
branchial arches and grooves
5 arches=> head and neck 1st & 2nd=> inner ear, pinna 1st: mandible, malleus and incus 1st groove: Concha/ external auditory meatus/ TM outer layer 2nd: face muscles, hyoid, stapes
___derms
endoderm- middle ear space LINING, E tube
mesoderm- middle ear space, ossicles
ectoderm- outer ear covering
outer ear: pinna parts and fn
cartilage and skin
from top: helix, triangular fossa, tragus, lobe, antitragus, concha cavum, anti helix, concha cymba
fn: acoustic imprint & resonance; localize, catch & direct sound into EAM
outer ear: EAM size, parts, fn
pinna=> Tm
25 cm L by 9mm H by 6.5mm D
fn: protect, provide resonance
outer: cartilaginous, cerumen, sebaceous, hair
inner: osseous, tympanic portion of temporal bone
outer ear: cerumen fn- TOCRAM
Repel water
Trap dust, sand particles, micro-organisms, and other debris
Moisturize epithelium in ear canal
Odor discourages insects
Antibiotic, antiviral, antifungal properties
Cleanse ear canal
outer ear: EAM problems
osseocartilaginous junction of two: mandible fits into temporal bone TMJ=> otalgia
stenosis
fungal/bacterial infex- swimmers ear, wax impaction
all cause a CONDUCTIVE HL
outer ear: tympanic membrane size, fn
border btw inner/middle ear 90mm^2, 17.5 mm diameter conical loudspeaker- middle ear transformer system middle ear pressure regulation rich blood supply
outer ear: tympanic membrane divisions
annulus- holds TM in place
pars flaccida- Top 15% of the TM, no fibers
pars tensa- all three layers Gives conical shape- cone of light reflection, Malleus
outer ear: tympanic membrane layers
outer: extensionf of EAM, Cutaneous stratum, skin over osseous meatus
Fiberous stratum: tough CT, concentric and radial fibers
inner: Mucosa Stratum=> middle ear
outer ear: tympanic membrane landmarks
manubrium (long portion) of malleus cone of light umbo- most depressed part of TM, long process of incus stapes
outer ear: resonance
air filled cavities have natural/resonant frequencies
each structure increases the sound pressure of said frequency by 10-12 dB
primary structures: concha (10 dB, best @ 5 kHz) and EAM (10dB, best @ 3 kHz) = 20 dB amplification
outer ear: localization
outer ear “encodes” vertical elevation of sound source in the amplification of the sound (+15 degrees azimuth= greater amp)
efficiency of sound collection encodes horizontal location (azimuth)- attenuation from back
examination HOP
history: trauma, allergy/sick, fly/dive, dizzy, hearing, duration
observation: red, swell, drain, object, cuts etc
palpation: press on tragus, traction on lobe and helix
otoscopic assessment procedure
1: sit, head down and away, cocked
2: largest comfortable speculum- snug, rest against
tragus
3. stabilize otoscope w ring and little finger “hammer or pencil”
4. pinna up and back to straighten canal
5. approach canal, watching through lens
6. rotate speculum to see TM
7. inspect color clarity position
8. identify landmarks
9. look for abnormalities
otoscopic assessment points
color: pearly gray
clarity: semitransparent
position: neither retracted nor bulging
landmarks: malleus, manubrium, short process, umbo, light reflex (cone), pars flaccida and tensa, annulus, stapes, incus
abnormalities: fluid, perforations
middle ear: parts and fn
chamber
bones- malleus incus stapes=> impedance match
muscles- stapedial, tensor tympani=> protection, compression of loud sounds (acoustic reflex)
ET (tensor/levator veli palatini)=> equalize air pressure, drainage
TM innervation
trigeminal>mandibular>Auriculo temporal nerve
Vagus nerve
Medial- glosspharyngeal nerve
Damage to facial nerve– may affect hearing as well
Damage to ear drum can also affect facial nerve- taste etc
middle ear bones (ossicles)
malleus- contacts TM
incus- middle
stapes- smallest, inner most, footplate rests in membranous oval window
suspended by axial ligaments
middle ear muscles: O, I, Fn
stapedius- O: posterior mastoid wall of tympanic cavity; I: stapes; CN 8-V; contracts w loud sound
tensor tympani- origin: anterior wall of cavity; insertion- malleus; CN 5-T; contracts with touch to lateral face, air pressure changes in EAM
ET specs
1/3 bone, 2/3 cartilaginous, 35 mm L, 45 degree angle
smaller, less steep in kids= poor drainage/opening= infex
impedance matching mechanism
30dB sound loss air sound to fluid sound, must be transformed thru middle ear “machine”
1) TM movement/lever= not much
2) malleus/incus lever 1.3:1
3) area ratio, TM: nail head as footplate: nail point, 17:1 area ratio but doesnt move as one unit (membrane)
P increase at stapes = 27.4 dB gain vs initial 30 dB loss
amplified frequencies
Little pressure amplification occurs for frequencies below 100 Hz or above 2000 to 2500 Hz, but 100-2500Hz is amplified
The outer ear amplifies sound energy by 20 dB for frequencies from 2000 to 5000 Hz (3000)
middle ear muscle contraction- acoustic reflex
in response to loud sound/touch results in attenuation of sounds by: 1) tightened TM 2) reduced trasnmission 3) draw malleus back consensual- both ears respond .03s-.04s delay
inner ear: parts
petrous portion of temporal bone osseous labyrinth- bony outer casing semicircular canals (sup, lat, pos) vestibule> oval window & round window cochlea
inner ear: balance
utricle and saccule: linear motion
semi circular canals: rotary/angular motion
inner ear: cochlea fn
end organ for hearing
breaks complex sounds into pure tones
tune and amplify incoming sounds
transmit info to central auditory nerve
inner ear: cochlea parts
snail shell, 2.5 turns around bony modiolus
bony labyrinth>membranous labyrinth>
three canals:
scala vestibuli (PL)> oval window, reisner’s mem
scala media (EL)> reisner’s mem, spiral ligament (clips), organ of corti, stria vascularis, basilar mem
scala tympani (PL)> round window
helicotrema port connects SV and ST
inner ear>cochlea>organ of corti
hearing organ
supporting cells- pillar, deiters, henson, claudius
sensory cells- single row of inner hair, more outer hair
under tectorial membrane above basilar membrane
inner ear>cochlea>tectorial membrane
90% water, gelatinous
projects from spiral limbus
longest sterocilia projections from OHC embed here
sound transmission
stapes footplate>oval window vibrates and establishes wave along basilar membrane> wave crests and decreases> depression of SM >BM displaced, shear the tectorial-embedded cilia of OHC> contracts and pulls Tect Mem down which in turn presses IHC> electrochemical processes> auditory nerve fibers
lower frequencies move/travel entire membrane- stimulates most responsive place
rate of discharge increases with intensity, but maxes at 30-40 dB, then recruits other neurons to express loudness up to 140 dB, density of action potentials encodes loudnes
inner ear>cochlea>basilar membrane
varies in width/stiff from base to apex
narrower and stiffer at base
creates tonotopic map
OHC vs IHC
OHC- more #, weak afferent, strong efferent, motor
IHC- fewer, sensory
central pathway- cannibals
Eighth nerve- aud branch Cochlear nuclear complex Superior olivary complex Lateral lemniscus Inferior colliculus Medial geniculate body Primary auditory cortex
cranial nerves- viking
Olfactory Optic Oculomotor Trochlear Trigeminal Abducens Vestibulocochlear Glossopharyngeal Vagus Accessory Hypoglossal
auditory nerve
cylindrical bundle
outer- basal turn of cochlear (high freq)
inner- apical turn (low freq)
cochlear nuclear complex- tooonic
dorsal
ventral
leave in 3 stria
fibers: onset, offset, onset/offset, tonic
super olivary complex-Soccer ball
relay
reflex- stapedius, tensor tympani
bilateral input
localization (from time/intensity differences)
lateral lemniscus- lilac
Ipsilateral IC projections but some to contra IC
lower brainstem Pathway
Afferent portion of auditory pathway
Connects SOC to IC
inferior colliculus- SMITS
SOCs stim midbrain ipsi MGB projection tonotopic 400k synapse- 2nd oblig
medial geniculate body- thick pac
thalamic nuc
422k tonotopic cells
primary aud cortex
primary auditory cortex- million TReeS
temporal lobes
representation of freq
10 million tonotopic cells
sylvian fissure
