Anatomy of the auditory system includes what structures?
Structures of the outer ear, middle ear and inner ear (p. 410)
Cartilage framed appendage covered w/ skin that appears around the 6th weak of gestation from 1st and 2nd branchial arches.
The Pinna (Auricle) (p. 410)
The external auditory meatus (EAM) is an s-shaped oval canal ___ to ___ mm in length. It opens at the ______ and terminates at the _____________.
25 to 33 mm
pinna
tympanic membrane
(p. 410)
The tympanic membrane does what?
It transduces sound (p. 410)
What is the function of the outer ear?
collects sounds and channels it to the middle ear. (p.410)
Besides auditory function, what other function does the OE serve?
protection
- cerumen ‘noxious’ to introders
- s-shape prevents foreign objects from reaching ME and TM (p. 411)
What does the ossicular chain consist of and what does it do?
3 bones (smallest in human body)
transfers the mechanical vibrations from TM to inner ear
p. 411
______= the most lateral ossicle, consisting of manubrium, head, neck and lateral and anterior processes; attached to the TM and the incus.
Malleus (p. 411)
______ = the middle and largest bone in the ossicular chain consisting of a body and a short, long, and lenticular process.
Incus (p. 411)
______= the most medial third and smallest ossicle consisting of a head, footplate, and 2 crura. The footplate is held in the oval window by annular ligament.
Stapes (p. 411)
What are the 2 muscles in the ME?
The tensor tympani and the stapedius muscle (p. 411)
Tensor tympani pulls malleus ______.
medially (p. 411)
Stapedius muscle (smallest muscle in body) pulls stapes _____ and tilts what?
posteriorly and tilts footplate in oval window (p. 411)
_________= mucosal lined pathway that ventilates the ME through the connection to the nasopharynx.
Eustachian tube (p. 411)
impedance mismatch = ?
loss of sound energy (p. 411)
How does the ME compensate for impedance mismatch? How much is compensated?
two primary mechanisms –> lever effect and ME muscles increase sensitivity
25 to 27 dB of estimated 30dB is compensated
(p. 411)
Complex structure residing within the petrous portion of the temporal bone
Inner ear (p. 411)
What are the 2 functions of the IE?
sense of hearing (cochlea) and sense of balance (semicircular canals and otolithic organs) (p. 411)
a bony canal that surrounds a membranous tube, about 35 mm in length and coils around central core approx 2 3/4 turns.
cochlea (p. 412)
________= upper canal running from oval window to helicotrema; contains perilymph
scala vestibuli (p. 412)
_______= lower canal running from the round window to helicotrema; contains perilymph
scala tympani (p. 412)
______= middle canal divided from scala vestibuli by Reissner’s membrane and from scala tympani by basilar membrane; contains organ of corti and contains endolymph.
scala media (p. 412)
The organ of corti consists of ?
sensory hair cells, support cells and support membranes and ligaments (p. 412)
How many (sensory) Outer Hair Cells (OHC) are there approx?
13,500 per ear; housed in 3 to 4 rows (p. 412)
The OHC serve as?
biologic modifier increasing or decreasing sensitivity to sounds by changing length of hair cells ( p. 412)
How many (sensory) Inner Hair Cells (IHC) are there approx?
3500 per ear housed in 1 row (p. 412)
The IHC serve as?
serve to process frequency, temporal and intensity info to auditory pathway (p. 413)
The basilar membrane yields what?
Tonotopicity in which high frequencies are processed at the base and low frequencies at the apex (p. 413)
What is the tectorial membrane responsible for?
For shearing the stereocilia of the hair cells (p. 413)
What is the main function of the IE?
Changes the mechanical energy into hyrdomechanical energy and then into neural impulses (p. 413)
Middle Ear contains what?
tympanic membrane Malleus Incus-Middle bone Stapes Tensor tympani Stapedius muscle Eustachian tube connects middle ear to nasopharynx
What does Inner Ear house?
Oval window
Labyrinths
Vestibular system
Cochlea
Cochlea
- -inner ear
- -Contains basilar membrane, organ of Corti, cilia
- -Receives wavelike movements that transform them into electrical energy that can stimulate nerve endings and carry sound to the brain
Oval window
- -inner ear
- -Beginning of inner ear
- -Small opening in temporal bone that houses inner ear.
Labyrinths
- -in inner ear
- -Interconnecting tunnels in inner ear that are filled with perilymph
Vestibular system
- -inner ear
- -3 semicircular canals responsible for equilibrium
What does Cranial nerve VIII do?
- -Vestibular branch-equilibrium and balance
- -Auditory branch-Supplies hair cells of cochlea and conducts electrical sound impulses from cochlea to brain
Speech frequencies
125-8,000Hz
Normal frequency for humans to hear
20-20,000 Hz
display disproportionately low word recognition in comparison to pure
tones, worst type of HL for word recognition, acoustic neuroma
Retrocochlear
What allows things to vibrate?
Elasticity and inertia
dip in audiogram at 2000 Hz due to stapes fixation
Carhart’s notch specifically with Bone conduction
faking it
Pseudohypacusis
-10-15 dB HL
normal
16-25 dB HL
slight
26-40 dB HL
mild
56-70 dB HL
moderately severe
71-90 dB HL
severe
91+ dB HL
Profound
Degrees of hearling loss (7)
normal slight mild moderate moderately severe severe profound
Hearing loss in which the sound is conducted the middle or inner ear is diminished.
Inner ear, acoustic nerve, auditory center are all working properly.
conductive
Hearing loss in which damage to the hair cells of the cochlea or to the acoustic nerve prevents the brain from receiving the neural impulses, Permanent
sensorineural
condition causing fluctuating sensorineural hearing loss
Meniere’s
Central Auditory Processing Disorder
- -Refers to effectiveness and efficiency with which the central nervous system uses auditory information
- -Disrupted sound transmission or disrupted ability to take in a message, interpret it, and make it meaningful.
- -Controversial
- -Poor auditory discrimination
decreases intensity of sound
attenuates
Types of assessment
- -pure tone
- -speech auditometry
- -acoustic immittance
- -tympanometry
- -electrocochleography
- -ABR
threshold
intensity in which tone is faintly heard 50% of time
Assessment:
- -Determines threshold
- -Types: Air conduction and Bone conduction
Pure tone Testing
Assessment:
- -Measures how well someone understands speech
- -Speech reception threshold
- -Spondee words
Speech Audiometry
Assessment:
- -Transfer of acoustic energy
- -Tympanic membrane and middle ear structures off impedance, or resistance to the flow of sound
- -Admittance is the counterpart of impedance
Acoustic Immittance
Assessment:
- -Procedure in which acoustic immittance is measured with an electroacoustic instrument
- -Measures changes in acoustic energy acoustic reflex is measured and is valuable in detecting middle ear diseases.
Tympanometry
Tympanomtery Scores
A As Ad C B
Tympanomtery Scores
A
normal
Tympanomtery Scores
As
shallow compliance
suggesting otosclerosis or beginign of an ear infection
Tympanomtery Scores
Ad
deep compliance
suggesting ossicular disarticulation
Tympanomtery Scores
C
negative pressure
suggesting eustachian tube dysfunction
Tympanomtery Scores
B
flat
no pressure or compliance
Assessment
- -measures electrical activity
- -records electrical activity in auditory nerve, brainstem and cortical areas of the brain.
- -Used to test newborns
ABR
Assessment of Infants and Children
Newborns: OAE and ABR
Infants: Localization techniques
Children: operant audiometry
Air bone gap
difference of 10 db or more, indicates conductive loss
Types of Amplificatn
- -hearing aids
- -cochlear implants
- -tactile aids
- -assistive devices
hearing aids
- -Amplifies sound and delivers it to ear canal
- -Includes microphones, receivers and amplifiers
Cochlear Implants
- -Electronic devices surgically placed in cochlear and deliver sound directly to the acoustic nerve endings in cochlea
- -Contains a microphone, processor, external transmitter and electrode
- -Used for people with minimal or no hearing, utilizes residual hearing.
Tactile Aids
- -Sensory substitution method for those who are deaf
- -Promote comprehension of speech by touch
Assistive Devices
- -Safety alerting devices
- -Closed-captioning
- -Telecommunication devices
Types of communication training for comprehension
auditory, speech reading, cued
Designed to teach a person with hearing impairments to listen to amplified sounds, recognize their meanings and discriminate sounds from each other
Auditory Training
Involves deciphering speech by looking at the face of the speaker and using visual cues to understand what the speaker is saying.
Speech Reading
Cued Speech
- -Produced with manual cues that represent sounds of speech
- -A form of sign language, but composed of only eight signs for consonants and four signs for vowels
Oral language training
Aural/oral method
Manual Approach
Total Commun.
ASL
Nonverbal communication and a language
ASL
Teaching both verbal and nonverbal approaches
Total Commun.
Means of nonverbal communication, whether it be signing or fingerspelling
manual approach
Use of amplification, auditory training, and speech reading in order to be mainstreamed into society.
Aural/oral method
A person with otosclerosis often has an audiogram reflecting Carhart’s notch. What is
Carhart’s notch?
A specific loss at 2,000 Hz, as indicated by bone-conduction testing