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Chapter 17, part 3. The Special Senses. SECTION 17-4 Equilibrium and Hearing. 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. - PowerPoint PPT Presentation
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Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Fundamentals of
Anatomy & PhysiologySIXTH EDITION
Frederic H
. Martini
PowerPoint® Lecture Slide Presentation prepared by Dr. Kathleen A. Ireland, Biology Instructor, Seabury Hall, Maui, Hawaii
Chapter 17, part 3
The Special Senses
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
SECTION 17-4 Equilibrium and Hearing
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Anatomy of the ear – External Ear
• Auricle or pinnae surrounds the ear
• External acoustic meatus ends on tympanic membrane
Both equilibrium and hearing are provided by receptors of the inner ear
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 17.20
Figure 17.20 The Anatomy of the Ear
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• Communicates with pharynx via pharyngotympanic membrane
• Middle ear encloses and protects the auditory ossicles
Middle ear
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Figure 17.21 The Middle Ear
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• Membranous labyrinth contains endolymph
• Bony labyrinth surrounds and protects membranous labyrinth
• Vestibule
• Semicircular canals
• Cochlea
Inner ear
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Figure 17.22 The Inner Ear
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• Vestibule contains the utricle and saccule
• Semicircular canals contain the semicircular ducts
• Cochlea contains the cochlear duct
Components of the inner ear
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• 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
Windows
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• 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)
Equilibrium
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Figure 17.23 The Vestibular Complex
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Figure 17.23 The Vestibular Complex
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Figure 17.23 The Vestibular Complex
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• Vestibular receptors activate sensory neurons of the vestibular ganglia
• Axons form the vestibular branch of cranial nerve VII
• Synapses within the vestibular nuclei
Vestibular neural pathway
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 17.24
Figure 17.24 Pathways for Equilibrium Sensation
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• 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
Hearing
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Figure 17.25 The Cochlea
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Figure 17.26 The Organ Of Corti
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• 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
Pathway of sound
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Figure 17.28 Sound and Hearing
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Figure 17.29 Sound and Hearing
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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
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
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.
