Figure 17-21 The Anatomy of the Ear External Ear Middle Ear Internal Ear Elastic cartilages Auditory ossicles Oval window Semicircular canals Petrous part of temporal bone Auricle Facial nerve (N VII) Vestibulocochlear nerve (N VIII) Bony labyrinth of internal ear Cochlea Tympanic cavity Auditory tube To nasopharynx External acoustic meatus Tympanic membrane Round window Vestibule 590 1

Figure 17-22a The Middle Ear. Auditory Ossicles Malleus Incus Stapes Temporal bone (petrous part) Stabilizing ligaments Oval window Muscles of the Middle Ear Branch of facial nerve VII (cut) Tensor tympani muscle External acoustic meatus Stapedius muscle Tympanic cavity (middle ear) Round window Auditory tube Tympanic membrane 592 a The structures of the middle ear

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Figure 17-22b The Middle Ear Malleus attached to tympanic membrane Tendon of tensor tympani muscle Malleus Incus Base of stapes at oval window Stapes Stapedius muscle Inner surface of tympanic membrane 592 The tympanic membrane and auditory ossicles 4

© 2015 Pearson Education, Inc. 593 © 2015 Pearson Education, Inc.

Figure 17-24a The Semicircular Ducts Vestibular branch (N VIII) Semicircular ducts Anterior Cochlea Ampulla Posterior Lateral Endolymphatic sac Endolymphatic duct Utricle Saccule Maculae An anterior view of the right semicircular ducts, the utricle, and the saccule, showing the locations of sensory receptors 596 6

Figure 17-25ab The Saccule and Utricle. Endolymphatic sac Endolymphatic duct Utricle Saccule a The location of the maculae Otoliths Gelatinous layer forming otolithic membrane Hair cells Nerve fibers 596 b The structure of an individual macula

Figure 17-25c The Saccule and Utricle Head in normal, upright position Gravity Head tilted posteriorly Gravity Otolith moves “downhill,” distorting hair cell processes Receptor output increases A diagrammatic view of macular function when the head is held horizontally and then tilted back 596 1 2 8

Figure 17-24a The Semicircular Ducts. Vestibular branch (N VIII) Semicircular ducts Anterior Cochlea Ampulla Posterior Endolymphatic sac Lateral Endolymphatic duct Utricle Maculae Saccule a An anterior view of the right semicircular ducts, the utricle, and the saccule, showing the locations of sensory receptors. 594

Figure 17-24b The Semicircular Ducts Ampulla filled with endolymph Cupula Hair cells Crista Supporting cells Sensory nerve A cross section through the ampulla of a semicircular duct 594 10

Figure 17-24c The Semicircular Ducts Direction of duct rotation Direction of relative endolymph movement Direction of duct rotation Semicircular duct Ampulla At rest Endolymph movement along the length of the duct moves the cupula and stimulates the hair cells. 594 11

Figure 17-24d The Semicircular Ducts Displacement in this direction stimulates hair cell Displacement in this direction inhibits hair cell Kinocilium Stereocilia 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. 594 12

Figure 17-26 Pathways for Equilibrium Sensations. To superior colliculus and relay to cerebral cortex Red nucleus N III Semicircular canals Vestibular ganglion N IV Vestibular branch Vestibular nucleus N VI To cerebellum Vestibule Cochlear branch N XI Vestibulocochlear nerve (VIII) 597 Vestibulospinal tracts

Vestibulocochlear nerve (VIII) Figure 17-27a The Cochlea. Round window Stapes at oval window Scala vestibuli Cochlear duct Scala tympani Semicircular canals KEY Cochlear branch Vestibular branch From oval window to tip of spiral Vestibulocochlear nerve (VIII) From tip of spiral to round window a The structure of the cochlea 598

598 Diagrammatic and sectional views of the cochlear spiral Figure 17-27b The Cochlea Temporal bone (petrous part) Vestibular membrane Scala vestibuli (contains perilymph) Tectorial membrane Cochlear duct (contains endolymph) Basilar membrane From oval window Spiral organ Spiral ganglion To round window Scala tympani (contains perilymph) Cochlear nerve Vestibulocochlear nerve (N VIII) 598 Diagrammatic and sectional views of the cochlear spiral 15

Figure 17-28a The Spiral Organ. Bony cochlear wall Scala vestibuli Spiral ganglion Vestibular membrane Cochlear duct Tectorial membrane Basilar membrane Scala tympani Spiral organ Cochlear branch of N VIII a A three-dimensional section of the cochlea, showing the compartments, tectorial membrane, and spiral organ 599

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 599 17

Figure 17-28b The Spiral Organ Cochlear duct (scala media) Vestibular membrane Tectorial membrane Scala tympani Basilar membrane Hair cells of spiral organ Spiral ganglion cells of cochlear nerve Spiral organ LM  125 Diagrammatic and sectional views of the receptor hair cell complex of the spiral organ 599 18

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Figure 17-31a Frequency Discrimination Stapes at oval window Cochlea 16,000 Hz 6000 Hz 1000 Hz Round window Basilar membrane The flexibility of the basilar membrane varies along its length, so pressure waves of different frequencies affect different parts of the membrane. 602 20

Figure 17-31b Frequency Discrimination Stapes moves inward Basilar membrane distorts toward round window Round window pushed outward 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. 602 21

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. 602 22

Figure 17-30 Sound and Hearing External acoustic meatus Malleus Incus Stapes Oval window Movement of sound waves Tympanic membrane Round 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. 601 23

Figure 17-30 Sound and Hearing (Part 2 of 2). Cochlear branch of cranial nerve VIII 6 Scala vestibuli (contains perilymph) Vestibular membrane Cochlear duct (contains endolymph) http://www.youtube.com/watch?v=lioNIbtFxSY&feature=related Basilar membrane 4 Scala tympani (contains perilymph) 5 4 5 6 The pressure waves distort the basilar membrane on their way to the round window of the scala tympani. Vibration of the basilar membrane causes hair cells to vibrate 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. 601

http://www.cidpusa.org/nervous%20system.htm

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Figure 17-32 Pathways for Auditory Sensations Stimulation of hair cells at a specific location along the basilar membrane activates sensory neurons. KEY Primary pathway Secondary pathway Motor output Cochlea Low-frequency sounds https://www.youtube.com/watch?v=PeTriGTENoc High-frequency sounds Vestibular branch Sensory neurons carry the sound information in the cochlear branch of the vestibulocochlear nerve (VIII) to the cochlear nucleus on that side. Vestibulocochlear nerve (VIII) 603 27

Figure 17-32 Pathways for Auditory Sensations Projection fibers then deliver the information to specific locations within the auditory cortex of the temporal lobe. High- frequency sounds Low-frequency sounds Thalamus Ascending acoustic information goes to the medial geniculate nucleus. The inferior colliculi direct a variety of unconscious motor responses to sounds. To cerebellum To reticular formation and motor nuclei of cranial nerves Information ascends from each cochlear nucleus to the inferior colliculi of the midbrain. KEY 603 Primary pathway Motor output to spinal cord through the tectospinal tracts Secondary pathway Motor output 28

603

Table 17-1 Intensity of Representative Sounds. 600

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