Transcript Hearing/Ear Power Point

Hole’s Human Anatomy
and Physiology
Twelfth Edition
Shier w Butler w Lewis
Chapter
12
Nervous System III: Senses
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1
Sense of Hearing
• Ear
• Organ of hearing
• Three (3) sections:
• External ear
• Middle ear
• Inner ear
2
External Ear
• Auricle
• Collects sounds
waves
• External auditory meatus
• Lined with
ceruminous glands
• Carries sound to
tympanic membrane
• Terminates with
tympanic membrane
• Tympanic membrane
• Vibrates in response
to sound waves
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Auricle
Semicircular
canals
Incus
Stapes
Malleus
Cochlea
Vestibulocochlear
nerve
Oval window
(under stapes)
Round window
Tympanic cavity
Tympanic
membrane
External acoustic
meatus
Auditory tube
Pharynx
3
Middle Ear
• Tympanic cavity
• Air-filled space in
Auricle
temporal bone
• Auditory ossicles
• Vibrate in response to
tympanic membrane
• Malleus, incus and stapes
• Hammer, anvil and stirrup
• Oval window
• Opening in wall of
tympanic cavity
• Stapes vibrates against it to
move fluids in inner ear
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Semicircular
canals
Incus
Stapes
Malleus
Cochlea
Vestibulocochlear
nerve
Oval window
(under stapes)
Round window
Tympanic cavity
Tympanic
membrane
External acoustic
meatus
Auditory tube
Pharynx
4
Auditory Tube
• Also known as the
Auricle
Eustachian tube
• Connects middle ear to
throat
• Helps maintain equal
pressure on both sides of
tympanic membrane
• Usually closed by valvelike flaps in throat
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Semicircular
canals
Incus
Stapes
Malleus
Cochlea
Vestibulocochlear
nerve
Oval window
(under stapes)
Round window
Tympanic cavity
Tympanic
membrane
External acoustic
meatus
Auditory tube
Pharynx
5
Inner Ear
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
• Complex system of
labyrinths
• Osseous labyrinth
• Bony canal in
temporal bone
• Filled with
perilymph
• Membranous labyrinth
• Tube within osseous
labyrinth
• Filled with
endolymph
Bony labyrinth
Perilymph
Membranous
labyrinth
Endolymph
Bony labyrinth
(contains perilymph)
Membranous labyrinth
(contains endolymph)
Semicircular
canals
Utricle
Vestibular nerve
Saccule
Cochlear nerve
Scala
vestibuli (cut)
Scala
tympani (cut)
Cochlear
duct (cut)
containing
endolymph
Ampullae
(a)
OvalVestibuleRoundMaculae
window
window
Cochlea
6
Inner Ear
• Three (3) parts of labyrinths:
• Cochlea
• Functions in hearing
Bony labyrinth
• Semicircular canals
(contains perilymph)
Membranous labyrinth
• Functions in
(contains endolymph)
equilibrium
Semicircular
canals
• Vestibule
• Functions in
equilibrium
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Bony labyrinth
Perilymph
Membranous
labyrinth
Endolymph
Utricle
Vestibular nerve
Saccule
Cochlear nerve
Scala
vestibuli (cut)
Scala
tympani (cut)
Cochlear
duct (cut)
containing
endolymph
Ampullae
(a)
OvalVestibuleRoundMaculae
window
window
Cochlea
7
Cochlea
• Scala vestibuli
• Upper compartment Stapes vibrating in
oval window
• Leads from oval
Scala vestibuli
filled with perilymph
window to apex of
Vestibular
spiral
membrane
• Part of bony labyrinth
Basilar
membrane
• Scala tympani
Scala tympani
with
• Lower compartment filled
perilymph
• Extends from apex of Round window
the cochlea to round
window
• Part of bony labyrinth
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Helicotrema
Membranous
labyrinth
Cochlear duct
filled with endolymph
8
Cochlea
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• Cochlear duct
• Portion of
membranous labyrinth
in cochlea
• Vestibular membrane
• Separates cochlear
duct from scala
vestibuli
• Basilar membrane
• Separates cochlear
duct from scala
tympani
Scala vestibuli
(contains perilymph)
Vestibular membrane
Branch of
cochlear
nerve
Cochlear duct
(contains endolymph)
Spiral organ (organ of Corti)
Basilar membrane
Scala tympani
(contains perilymph)
(a)
9
12.4 Clinical Application
Getting a Cochlear Implant
10
Organ of Corti
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• Group of hearing receptor
cells (hair cells)
• On upper surface of basilar
membrane
• Different frequencies of
vibration move different parts
of basilar membrane
• Particular sound frequencies
cause hairs of receptor cells to
bend
• Nerve impulse generated
Scala vestibuli
(contains perilymph)
Vestibular membrane
Cochlear duct
(contains endolymph)
Branch of
cochlear
nerve
Spiral organ (organ of Corti)
Basilar membrane
Scala tympani
(contains perilymph)
(a)
Tectorial
membrane
Hair cells
Basilar
membrane
(b)
Branch of
cochlear nerve
Nerve
fibers
Supporting
cells
11
Organ of Corti
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Cochlear duct
Tectorial membrane
Scala tympani
Hair cells
Basilar
membrane
(a)
(b)
a: © John D. Cunningham/Visuals Unlimited; b: © Fred Hossler/Visuals Unlimited
12
Auditory Nerve Pathways
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Auditory cortex
(temporal lobe)
Thalamus
Medial geniculate
body of thalamus
Midbrain
Pons
Superior
olivary
nucleus
Medulla
oblongata
Cochlear
nuclei
Vestibulocochlear
nerve
13
12.5 Clinical Application
Hearing Loss
14
Summary of the Generation of
Sensory Impulses from the Ear
15
Sense of Equilibrium
• Static equilibrium
• Vestibule
• Senses position of
head when body is not
moving
• Dynamic Equilibrium
• Semicircular canals
• Senses rotation and
movement of head and
body
16
Vestibule
• Utricle
• Communicates with
saccule and membranous
portion of semicircular Ampullae of
semicircular
canals
canals
• Saccule
• Communicates with
cochlear duct
• Macula
• Hair cells of utricle and
saccule
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Vestibulocochlear
nerve
Cochlea
Utricle
Cochlear
duct
Maculae Saccule Vestibule
17
Macula
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• Responds to changes
in head position
• Bending of hairs
results in generation of
nerve impulse
Hairs of
hair cells bend
Gelatinous
material sags
Otoliths
Macula
of utricle
Hair cells
Sensory (afferent) nerve fiber
Gravitational
force
Supporting cells
18
(a) Head upright
(b) Head bent forward
Semicircular Canals
• Three (3) canals at right angles
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• Ampulla
• Swelling of membranous
Vestibulocochlear
labyrinth that communicates Ampullae of
nerve
semicircular
Cochlea
Utricle
with the vestibule
canals
Cochlear
• Crista ampullaris
duct
• Sensory organ of ampulla
• Hair cells and supporting cells
• Rapid turns of head or body
stimulate hair cells
Maculae Saccule
Vestibule
19
Crista Ampullaris
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Endolymph
Semicircular canal
Cupula
Crista
ampullaris
(a) Head in still position
Ampulla
Crista ampullaris
Hairs
Hair cell
Supporting cells
Sensory (afferent)
nerve fibers
(b) Head rotating
(c)
20