Transcript CSD 3103/FALL 2002 ANATOMY OF SPEECH AND HEARING

CSD 3103
anatomy of speech and hearing
mechanisms
Hearing mechanisms
Fall 2008
The Inner Ear
The major divisions of the
inner ear

The vestibular system

The cochlea

The osseous or bony labyrinth

The membranous labyrinth
Location of the inner
ear within the skull
Cross section of the inner ear
The bony labyrinth
The bony labyrinth
The cochlea
Modiolus
Internal auditory
meatus
Auditory nerve
Facial nerve
Modiolus and internal
auditory meatus
The cochlea
 Scala vestibuli
 Scala tympani
 Scala media
 Helicotrema
 Perilymph
The membranous
labyrinth
The membranous labyrinth in relation to the bony labyrinth
The membranous
labyrinth
Endolymph
Semicircular
canals
Utricle
Saccule
Scala media
The membranous
labyrinth
Ampullae
Crista ampularis
Ductus Reuiens
The cochlear duct
Cross section of the
cochlea
Eighth Nerve
Vestibular branch
Acoustic branch
Base
Apex
Modiolus
Helicotrema
Scala Vestibuli, Tympani and
Media
Basilar Membrane
Reissner’s Membrane
Spiral Lamina
Spiral lamina
Cochlear partitions
An “unrolled” cochlea, showing the relationships among the
three scalae
Cochlear partitions
Cochlear cross-section
Cochlear duct and
the organ of corti
Cochlear duct and
the organ of corti
organ of corti
organ of corti
Inner hair cell
Outer hair cell
Path of vibration
through the cochlea
Vibrations are transmitted across scala media into scala
tympani
Mass-action flow
through the cochlea
Inward movement of the stapes footplate causes perilymph to flow up
scala vestibuli, through the helicotrema, and down scala tympani,
where the round window is distended
Displacement of the
basilar and tectorial
membranes
The vertical displacement of the basilar and tectorial
membranes produces a shearing force on the cilia of
the hair cells
Basilar membrane
displacement
Relative motion between the basilar and tectorial membranes places a
shearing force on the stereocilia so they are bent away from the
modiolus when the cochlear duct is displaced upward
Cochlear function
Movement of the
basilar membrane
Schematic representation of the
cochlea with the vestibule cut
away. Arrows show the effects
of a compressional sound
wave produced by the stapes.
Example of the position of a
portion of the basilar
membrane in 3 successive
instants during sinusoidal
stimulation.
Traveling wave
Characteristics of the traveling wave generated by a 200
Hz stimulus peaking at a distance of about 29mm from
the base of the cochlea
Traveling wave envelopes for
three different frequencies
The traveling wave
Schematic of amplitude
patterns of traveling
waves for sinusoids of
various frequencies
Traveling wave response as a
function of frequency
Place coding mechanism
of the cochlea
Place-by-frequency
conversion along the
basilar membrane
Organization of the
cochlea
Tonotopic organization relates to the placement of
auditory neurons in a particular structure (in this
case, the cochlea) according to their
responsiveness to specific frequencies