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The Special Senses

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The Special Senses HOMEWORK DUE IN LAB 5 HW page 9: Matching Eye Disorders PreLab 5 THE SPECIAL SENSES Hearing and Equilibrium THE EAR The organ of hearing and equilibrium . Cranial nerve VIII - Vestibulocochlear . Regions . External ear . Middle ear . Internal ear (labyrinth) Middle Internal ear External ear (labyrinth) ear Auricle (pinna) Helix Lobule External acoustic Tympanic Pharyngotympanic meatus membrane (auditory) tube (a) The three regions of the ear Figure 15.25a Middle Ear Epitympanic Superior Malleus Incus recess Lateral Anterior View Pharyngotym- panic tube Tensor Tympanic Stapes Stapedius tympani membrane muscle muscle (medial view) Copyright © 2010 Pearson Education, Inc. Figure 15.26 MIDDLE EAR Auditory tube . Connects the middle ear to the nasopharynx . Equalizes pressure . Opens during swallowing and yawning . Otitis media INNER EAR Contains functional organs for hearing & equilibrium . Bony labyrinth . Membranous labyrinth Superior vestibular ganglion Inferior vestibular ganglion Temporal bone Semicircular ducts in Facial nerve semicircular canals Vestibular nerve Anterior Posterior Lateral Cochlear Cristae ampullares nerve in the membranous Maculae ampullae Spiral organ Utricle in (of Corti) vestibule Cochlear duct Saccule in in cochlea vestibule Stapes in Round oval window window Figure 15.27 INNER EAR - BONY LABYRINTH Three distinct regions . Vestibule . Gravity . Head position . Linear acceleration and deceleration . Semicircular canals . Angular acceleration and deceleration . Cochlea . Vibration Superior vestibular ganglion Inferior vestibular ganglion Temporal bone Semicircular ducts in Facial nerve semicircular canals Vestibular nerve Anterior Posterior Lateral Cochlear Cristae ampullares nerve in the membranous Maculae ampullae Spiral organ Utricle in (of Corti) vestibule Cochlear duct Saccule in in cochlea vestibule Stapes in Round oval window window Figure 15.27 INNER EAR The cochlea . A spiral, conical, bony chamber . Vestibular canal (scala vestibuli) . Cochlear duct (scala media) . Tympanic canal (scala tympani) Modiolus Cochlear nerve, division of the vestibulocochlear nerve (VIII) Spiral ganglion Osseous spiral lamina Vestibular membrane Cochlear duct (scala media) (a) Helicotrema Figure 15.28a INNER EAR Cavity of the cochlea is divided into 3 chambers Vestibular canal (scala vestibuli) Vestibular membrane Cochlear duct (scala media) Basilar membrane supporting Organ of Corti Tympanic canal (scala tympani) Vestibular membrane Osseous spiral lamina Tectorial membrane Scala Spiral Cochlear duct vestibuli ganglion (scala media; (contains contains perilymph) endolymph) Stria vascularis Spiral organ (of Corti) Scala tympani Basilar (contains membrane perilymph) (b) Copyright © 2010 Pearson Education, Inc. Figure 15.28b Organ of Corti Tectorial membrane Inner hair cell Hairs (stereocilia) Afferent nerve fibers Outer hair cells Supporting cells Fibers of cochlear nerve Basilar membrane (c) Figure 15.28c PHYSIOLOGY OF HEARING Transduction of sound Mechanical energy in middle ear Fluid pressure wave in inner ear Nerve impulse PHYSIOLOGY OF HEARING IN A NUTSHELL Sounds set up vibrations in air that beat against the eardrum that pushes a chain of tiny bones that press fluid in the internal ear against membranes that set up shearing forces that pull on the tiny hair cells that stimulate nearby neurons that give rise to the impulses that travel to the brain – and you hear. (This is from your textbook) Area of high pressure (compressed molecules) Area of Wavelength low pressure (rarefaction) Crest Trough Air pressureAir Distance Amplitude A struck tuning fork alternately compresses and rarefies the air molecules around it, creating alternate zones of high and low pressure. (b) Sound waves radiate outward in all directions. Figure 15.29 High frequency (short wavelength) = high pitch Low frequency (long wavelength) = low pitch Pressure Time (s) (a) Frequency is perceived as pitch. High amplitude = loud Low amplitude = soft Pressure Time (s) (b) Amplitude (size or intensity) is perceived as loudness. Copyright © 2010 Pearson Education, Inc. Figure 15.30 Malleus Incus Stapes vibrating Helicotrema Cochlea in oval window Sound waves Perilymph 3 8 Scala 7 4 tympani Scala 5 vestibuli 6 Basilar 1 2 9 membrane External auditory 8 canal Spiral organ (organ of Corti) Tectorial membrane Vestibular membrane Cochlear duct Tympanic (contains endolymph) membrane Secondary tympanic membrane vibrating Middle ear Auditory tube in round window Auditory ossicles Malleus Incus Stapes Cochlear nerve Scala vestibuli Oval Helicotrema window Scala tympani Cochlear duct 2 3 Basilar membrane 1 Sounds with frequencies below hearing travel through the helicotrema and do not Tympanic Round excite hair cells. membrane window Sounds in the hearing range (a) Route of sound waves through the ear go through the cochlear duct, 1 Sound waves vibrate 3 Pressure waves created by vibrating the basilar membrane the tympanic membrane. the stapes pushing on the oval and deflecting hairs on inner 2 Auditory ossicles vibrate. window move through fluid in hair cells. Pressure is amplified. the scala vestibuli. Copyright © 2010 Pearson Education, Inc. Figure 15.31a Basilar membrane High-frequency sounds displace the basilar membrane near the base. Fibers of basilar membrane Medium-frequency sounds displace the basilar membrane near the middle. Base Apex (short, (long, stiff floppy fibers) fibers) Low-frequency sounds displace the basilar membrane near the apex. Frequency (Hz) (b) Different sound frequencies cross the basilar membrane at different locations. Copyright © 2010 Pearson Education, Inc. Figure 15.31b Tectorial membrane Inner hair cell Hairs (stereocilia) Afferent nerve fibers Outer hair cells Supporting cells Fibers of cochlear nerve Basilar membrane (c) Copyright © 2010 Pearson Education, Inc. Figure 15.28c Medial geniculate nucleus of thalamus Primary auditory cortex in temporal lobe Inferior colliculus Lateral lemniscus Superior olivary nucleus Midbrain (pons-medulla junction) Cochlear nuclei Medulla Vibrations Vestibulocochlear nerve Vibrations Spiral ganglion of cochlear nerve Bipolar cell Spiral organ (of Corti) Figure 15.33 LOCALIZATION OF SOUND Timing comparison . Side nearest sound detects sound first Comparison of volume . High pitched = blocked by head . Low pitched = curve around head ABNORMALITIES OF HEARING Conductive deafness . Interference in movement of middle ear bones . Impacted earwax, perforated eardrum or otosclerosis of the ossicles Sensorineural deafness . Damage to the neural structures . Aging, prolonged exposure to loud sounds ABNORMALITIES OF HEARING Otitis media ABNORMALITIES OF HEARING Otosclerosis ABNORMALITIES OF HEARING Meniere’s Disease ABNORMALITIES OF HEARING Tinnitus PHYSIOLOGY OF EQUILIBRIUM Information about position and movement of head . Vestibular apparatus . Utricle Vesibule . Saccule . Semi-circular canals Vestibular Apparatus Otoliths Kinocilium Otolithic Stereocilia membrane Hair bundle Macula of utricle Macula of saccule Hair cells Maculae are Supporting perpendicular cells to one another Vestibular nerve fibers Figure 15.34 VESTIBULE Macula .Utricle . Horizontal movements . Tilting the head side to side .Saccule . Vertical movements SEMI-CIRCULAR CANALS . Crista ampullaris . Sensory receptor for dynamic equilibrium . One in the ampulla of each semicircular canal . Major stimuli are rotatory movements Cupula Crista ampullaris Endolymph Hair bundle (kinocilium plus stereocilia) Hair cell Membranous Crista labyrinth ampullaris Supporting Fibers of vestibular nerve cell (a) Anatomy of a crista ampullaris in a semicircular canal Cupula (b) Scanning electron micrograph of a crista ampullaris (200x) Copyright © 2010 Pearson Education, Inc. Figure 15.36a–b MOTION SICKNESS Conflicts between eye movements and equilibrium . Nystagmus . Slow component . Fast component .
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