Download 17-03_pptlect

Anatomy & Physiology
SIXTH EDITION
Chapter 17, part 3
The Special Senses
PowerPoint® Lecture Slide Presentation prepared by
Dr. Kathleen A. Ireland, Biology Instructor, Seabury Hall, Maui, Hawaii
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Frederic H. Martini
Fundamentals of
SECTION 17-4
Equilibrium and Hearing
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Both equilibrium and hearing are provided by
receptors of the inner ear
Anatomy of the ear – External Ear
• Auricle or pinnae surrounds the ear
• External acoustic meatus ends on tympanic
membrane
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Figure 17.20 The Anatomy of the Ear
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Figure 17.20
Middle ear
• Communicates with pharynx via
pharyngotympanic membrane
• Middle ear encloses and protects the auditory
ossicles
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Figure 17.21 The Middle Ear
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Figure 17.21
Inner ear
• Membranous labyrinth contains endolymph
• Bony labyrinth surrounds and protects
membranous labyrinth
• Vestibule
• Semicircular canals
• Cochlea
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Figure 17.22 The Inner Ear
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Figure 17.22
Components of the inner ear
• Vestibule contains the utricle and saccule
• Semicircular canals contain the semicircular
ducts
• Cochlea contains the cochlear duct
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Windows
• Round window separates the perilymph from the
air spaces of the middle ear
• Oval window connected to the base of the stapes
• Basic receptors of inner ear are hair cells
• Provide information about the direction and
strength of stimuli
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Equilibrium
• Anterior, posterior and lateral semicircular ducts
are continuous with the utricle
• Each duct contains an ampulla with a
gelatinous cupula and associated sensory
receptor
• Saccule and utricle connected by a passageway
continuous with the endolymphatic duct
• Terminates in the endolymphatic sac
• Saccule and utricle have hair cells clustered in
maculae
• Cilia contact the otolith (statoconia)
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Figure 17.23 The Vestibular Complex
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Figure 17.23a, b, & d
Figure 17.23 The Vestibular Complex
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Figure 17.23c
Figure 17.23 The Vestibular Complex
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Figure 17.23e
Vestibular neural pathway
• Vestibular receptors activate sensory neurons of
the vestibular ganglia
• Axons form the vestibular branch of cranial nerve
VII
• Synapses within the vestibular nuclei
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Figure 17.24 Pathways for Equilibrium
Sensation
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Figure 17.24
Hearing
• Cochlear duct lies between the vestibular duct
and the tympanic duct
• Hair cells of the cochlear duct lie within the
Organ of Corti
• Intensity is the energy content of a sound
• Measured in decibels
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Figure 17.25 The Cochlea
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Figure 17.25a, b
Figure 17.26 The Organ Of Corti
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Figure 17.26a, b
Pathway of sound
• Sound waves travel toward tympanic membrane,
which vibrates
• Auditory ossicles conduct the vibration into the
inner ear
• Tensor tympani and stapedius muscles contract
to reduce the amount of movement when loud
sounds arrive
• Movement at the oval window applies pressure to
the perilymph of the cochlear duct
• Pressure waves distort basilar membrane
• Hair cells of the Organ of Corti are pushed against
the tectoral membrane
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Figure 17.28 Sound and Hearing
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Figure 17.28a
Figure 17.29 Sound and Hearing
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Figure 17.29
Neural pathway
• Sensory neurons of hearing are located in the
spiral ganglion of the cochlea
• Afferent fibers form the cochlear branch of
cranial nerve VIII
• Synapse at the cochlear nucleus
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You should now be familiar with:
• The sensory organs of smell, and the olfactory
pathways in the brain.
• The accessory and internal structures of the eye,
and their functions.
• How light stimulates the production of nerve
impulses, and the visual pathways.
• The structures of the external and middle ear and
how they function.
• The parts of the inner ear and their roles in
equilibrium and hearing.
• The pathways for the sensations of equilibrium and
hearing.
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings