© 2012 Pearson Education, Inc. Figure The Anatomy of the Ear External Ear Elastic cartilages Auricle External acoustic meatus Tympanic membrane Tympanic cavity Middle Ear Auditory ossicles Oval window Semicircular canals Petrous part of temporal bone Facial nerve (N VII) Cochlea Vestibulocochlear nerve (N VIII) Bony labyrinth of internal ear Auditory tube To nasopharynx Vestibule Round window Internal Ear p.575

© 2012 Pearson Education, Inc. Figure 17-22a The Middle Ear Temporal bone (petrous part) Malleus IncusStapes Oval window Muscles of the Middle Ear Tensor tympani muscle Stapedius muscle Round window Auditory tube Stabilizing ligaments Branch of facial nerve VII (cut) External acoustic meatus Tympanic cavity (middle ear) Tympanic membrane The structures of the middle ear. Auditory Ossicles p.576

Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings © 2012 Pearson Education, Inc. p.576

© 2012 Pearson Education, Inc. Figure 17-22b The Middle Ear Tendon of tensor tympani muscle Malleus Malleus attached to tympanic membrane Incus Base of stapes at oval window Stapes Stapedius muscle Inner surface of tympanic membrane The tympanic membrane and auditory ossicles p.576

Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings © 2012 Pearson Education, Inc. p.577

© 2012 Pearson Education, Inc. Figure 17-24a The Semicircular Ducts Semicircular ducts Anterior Lateral Posterior Ampulla Utricle Saccule Maculae Vestibular branch (N VIII) Cochlea Endolymphatic sac Endolymphatic duct An anterior view of the right semicircular ducts, the utricle, and the saccule, showing the locations of sensory receptors p.579

© 2012 Pearson Education, Inc. Figure 17-25ab The Saccule and Utricle The location of the maculae Otolith Nerve fibers Hair cells Statoconia Gelatinous material The structure of an individual macula p.580

© 2012 Pearson Education, Inc. Figure 17-25c The Saccule and Utricle Head in normal, upright position Gravity Head tilted posteriorly Receptor output increases Otolith moves “downhill,” distorting hair cell processes A diagrammatic view of macular function when the head is held horizontally and then tilted back 21 p.580

© 2012 Pearson Education, Inc. Figure 17-24b The Semicircular Ducts Cupula A cross section through the ampulla of a semicircular duct Crista Supporting cells Sensory nerve Ampulla filled with endolymph Hair cells p.579

© 2012 Pearson Education, Inc. Figure 17-24c The Semicircular Ducts Endolymph movement along the length of the duct moves the cupula and stimulates the hair cells. At rest Direction of duct rotation Direction of relative endolymph movement Semicircular duct Direction of duct rotation Ampulla p.579

© 2012 Pearson Education, Inc. Figure 17-24d The Semicircular Ducts Stereocilia Kinocilium Hair cell Sensory nerve ending Supporting cell A representative hair cell (receptor) from the vestibular complex. Bending the sterocilia toward the kinocilium depolarizes the cell and stimulates the sensory neuron. Displacement in the opposite direction inhibits the sensory neuron. Displacement in this direction inhibits hair cell Displacement in this direction stimulates hair cell p.579

© 2012 Pearson Education, Inc. Figure Pathways for Equilibrium Sensations Vestibular ganglion Vestibular branch Red nucleus Semicircular canals Vestibule Cochlear branch N VI N IV N III Vestibular nucleus N XI Vestibulocochlear nerve (N VIII) To cerebellum Vestibulospinal tracts To superior colliculus and relay to cerebral cortex p.581

Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings © 2012 Pearson Education, Inc. p.582

© 2012 Pearson Education, Inc. Figure 17-27b The Cochlea Vestibular membrane Tectorial membrane Basilar membrane From oval window To round window Temporal bone (petrous part) Scala vestibuli (contains perilymph) Cochlear duct (contains endolymph) Spiral organ Spiral ganglion Scala tympani (contains perilymph) Cochlear nerve Vestibulocochlear nerve (N VIII) Diagrammatic and sectional views of the cochlear spiral p.582

© 2012 Pearson Education, Inc. Figure 17-28a The Spiral Organ A three-dimensional section of the cochlea, showing the compartments, tectorial membrane, and spiral organ Cochlear branch of N VIII Spiral ganglion Body cochlear wall Scala vestibuli Vestibular membrane Cochlear duct Tectorial membrane Basilar membrane Scala tympani Spiral organ p.583

© 2012 Pearson Education, Inc. Figure 17-28b The Spiral Organ Tectorial membrane Outer hair cell Basilar membrane Inner hair cell Nerve fibers Diagrammatic and sectional views of the receptor hair cell complex of the spiral organ p.583

© 2012 Pearson Education, Inc. Figure 17-28b The Spiral Organ Diagrammatic and sectional views of the receptor hair cell complex of the spiral organ Spiral organ Cochlear duct (scala media) Basilar membrane Hair cells of spiral organ Spiral ganglion cells of cochlear nerve LM  125 Vestibular membrane Tectorial membrane Scala tympani p.583

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© 2012 Pearson Education, Inc. Figure 17-31a Frequency Discrimination Stapes at oval window Round window 16,000 Hz Basilar membrane Cochlea 6000 Hz1000 Hz The flexibility of the basilar membrane varies along its length, so pressure waves of different frequencies affect different parts of the membrane. p.586

© 2012 Pearson Education, Inc. Figure 17-31b Frequency Discrimination Stapes moves inward Round window pushed outward Basilar membrane distorts toward round window The effects of a vibration of the stapes at a frequency of 6000 Hz. When the stapes moves inward, as shown here, the basilar membrane distorts toward the round window, which bulges into the middle-ear cavity. p.586

© 2012 Pearson Education, Inc. Figure 17-31c Frequency Discrimination Stapes moves outward Round window pulled inward Basilar membrane distorts toward oval window When the stapes moves outward, as shown here, the basilar membrane rebounds and distorts toward the oval window. p.586

© 2012 Pearson Education, Inc. Figure Sound and Hearing External acoustic meatus Malleus Incus Movement of sound waves Tympanic membrane Round window Stapes Oval window Sound waves arrive at tympanic membrane. Movement of the tympanic membrane causes displacement of the auditory ossicles. Movement of the stapes at the oval window establishes pressure waves in the perilymph of the scala vestibuli. p.585

© 2012 Pearson Education, Inc. Figure Sound and Hearing Cochlear branch of cranial nerve VIII Scala vestibuli (contains perilymph) Vestibular membrane Cochlear duct (contains endolymph) Scala tympani (contains perilymph) The pressure waves distort the basilar membrane on their way to the round window of the scala tympani. Vibration of the basilar membrane causes vibration of hair cells against the tectorial membrane. Information about the region and the intensity of stimulation is relayed to the CNS over the cochlear branch of cranial nerve VIII. Basilar membrane p.585

© 2012 Pearson Education, Inc. Figure Sound and Hearing Cochlear branch of cranial nerve VIII Scala vestibuli (contains perilymph) Vestibular membrane Cochlear duct (contains endolymph) Scala tympani (contains perilymph) The pressure waves distort the basilar membrane on their way to the round window of the scala tympani. Vibration of the basilar membrane causes vibration of hair cells against the tectorial membrane. Information about the region and the intensity of stimulation is relayed to the CNS over the cochlear branch of cranial nerve VIII. Basilar membrane p.585

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© 2012 Pearson Education, Inc. Figure Pathways for Auditory Sensations Stimulation of hair cells at a specific location along the basilar membrane activates sensory neurons. Cochlea Low-frequency sounds High-frequency sounds Vestibular branch KEY Sensory neurons carry the sound information in the cochlear branch of the vestibulocochlear nerve (VIII) to the cochlear nucleus on that side. Primary pathway Secondary pathway Motor output Vestibulocochlear nerve (VIII) p.587

© 2012 Pearson Education, Inc. Figure Pathways for Auditory Sensations KEY Primary pathway Secondary pathway Motor output Motor output to spinal cord through the tectospinal tracts To reticular formation and motor nuclei of cranial nerves Information ascends from each cochlear nucleus to the inferior colliculi of the midbrain. The inferior colliculi direct a variety of unconscious motor responses to sounds. Ascending acoustic information goes to the medial geniculate nucleus. Low-frequency sounds High- frequency sounds Thalamus Projection fibers then deliver the information to specific locations within the auditory cortex of the temporal lobe. To cerebellum p.587

Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings p.587

© 2012 Pearson Education, Inc. Table 17-1 Intensity of Representative Sounds p.584

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