Outer Ear main purpose is to funnel sound waves to inner ear 1a Auricle gathers sound waves 1b External acoustic meatus transmits sound waves to tympanic membrane 1c Tympanic membrane ID: 774678
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Slide1
The Ear and Hearing
Slide21. Outer Ear- main purpose is to funnel sound waves to inner ear.1a. Auricle-gathers sound waves 1b. External acoustic meatus- transmits sound waves to tympanic membrane1c. Tympanic membrane (eardrum)-amplifies sound and transmits it to middle ear.
Slide32.
Middle Ear (tympanic cavity)-
main purpose is to transmit sound waves through movement and vibration of the
ossicles
(bones) to the inner ear.
2a.
Malleus
-receives sound waves from eardrum
2b.
Incus
-transmits sound waves to stapes
2c.
Stapes
-transmits sound waves to oval window
2d.
Auditory tube
(Eustachian tube)-connects middle ear to throat and helps maintain air pressure
2e.
Tympanic cavity-
air filled cavity that connects to the auditory tube
Slide44
Fig10.07
Stapes
Incus
Malleus
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© The McGraw-Hill Companies, Inc./Jim Womack, photographer
Slide53. Inner Ear- major purpose is to generate movement of tiny hair like cells with a fluid called endolymph and perilymph to transmit impulses to the brain through nerves.3a. Oval window -receives amplified sounds waves from stapes.3b. Round window-opening to inner ear, moves opposite oval window to ensure fluid moves in cochlea.3c. Cochlea-hearing, hair cells detect frequency of sound3d. Cochlear nerve -sends information about sound to brain3e. Vestibular nerve -sends information about the heads position to brain3f. Vestibule-detects static equilibrium (the position of the head when still)3g. Semicircular canals -detect dynamic equilibrium (motion of head) and aids in balance
Slide66
Fig10.08
Semicircular
canals
Cochlear nerve
Maculae
Utricle
Vestibular nerve
Membranous labyrinth
(contains endolymph)
Osseous labyrinth
(contains perilymph)
Cochlea
Cochlear
duct (cut)
containing
endolymph
Scala
chambers (cut)
containing
perilymph
Round
window
Saccule
Oval
window
Ampullae
Endolymph
Perilymph
Membranous labyrinth
Osseous labyrinth
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Slide7Slide8Slide9Slide10Video Links
How
Hearing
Works
Conductive Hearing Loss
Sensorineural
Hearing Loss
Cochlear Implants
Slide11I
. HOW WE HEAR
A.
The outer ear
-
funnels sound waves of a given frequency (measured in hertz) and intensity (measured in decibels) to the tympanic membrane, causing it to vibrate.
B.
Vibration of the tympanic membrane
causes
vibrations in the
middle ear
ossicles
(tiny bones)-
malleus
,
incus
and stapes, which vibrates the oval window of the cochlea.
C
. Vibration of the oval window sets up a traveling wave of
perilymph
in the vestibule of the
inner ear
. The wave passes through the cochlear duct- filled with
endolymph
.
Slide12D. The sensory structure of the cochlea is called the
organ of
Corti
.
1.
Organ
of
Corti
-
consists of sensory hair cells on the basilar membrane. The hair cells send messages to
vestibulocochlear
nerve when stimulated.
2.
High frequency sounds
- cause maximal displacement of the basilar membrane-
closer to its base near the stapes.
3.
Low
frequency sounds
- produce maximal displacement of the basilar membrane closer to its apex.
4.
Pitch discrimination
-- depends on the region of the basilar membrane that vibrates maximally to sounds of different frequency.
Slide13Hearing Loss
Conductive hearing loss
-something is inhibiting the sound waves from reaching the inner ear
Malformation of outer ear, ear canal, or middle ear structures.
Fluid in the middle ear from colds.
Ear
infection.
Allergies.
Poor Eustachian tube function.
Perforated eardrum
.
Slide14Hearing Loss
Sensorineural hearing loss
-indicates the malfunction of the inner ear in conducting the message to the brain
.
Exposure to loud noise.
Head trauma.
Virus or disease.
Autoimmune inner ear disease.
Hearing loss that runs in the family.
Aging (
presbycusis
)
Malformation of the inner ear.
Meniere's Disease.
Slide15Hearing Loss Limits
Slide16iPOD Listening Times
Slide17Exposures >85 dB for more than 10 minutes at a time may cause hearing loss
Slide18