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Human Biology Sylvia S. Mader Michael Windelspecht Chapter 14 Senses Lecture Outline Part 3 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1 14.5 Sense of Hearing 1. Divisions of the ear: Outer ear • Includes – ______: the external ear flap that catches sound waves – ____________: directs sound waves to the tympanic membrane • Lined with fine hairs and modified sweat glands that secrete ear wax 2 14.5 Sense of Hearing 2. Divisions of the ear: Middle ear • Includes – _______________ (eardrum): membrane that vibrates to carry sound waves to the bones – __________ (malleus, incus, stapes): 3 small bones that amplify sound waves – __________ (Eustachian tube): a tube that connects from the throat to the middle ear and is used to equalize pressure so the eardrum does not burst 3 14.5 Sense of Hearing Following the sound wave Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Outer ear Middle ear Inner ear stapes semicircular canals incus malleus oval window vestibule vestibular nerve pinna cochlear nerve cochlea tympanic membrane auditory canal temporal bone round window auditory tube Figure 14.12 The three divisions of the human ear. 4 14.5 Sense of Hearing 3. Divisions of the ear: Inner ear • Important for both hearing and balance • 3 areas: cochlea, semicircular canals, vestibule • _______ (middle ear bone) – vibrates and strikes the membrane of the oval window causing fluid waves in the cochlea • _______ – functions in gravitational equilibrium • _________ – functions in rotational equilibrium 5 14.5 Sense of Hearing The inner ear: The cochlea • The cochlea converts vibrations into nerve impulses. • It contains the spiral organ (organ of Corti) which is the sense organ containing hairs for hearing. – Bending of embedded hairs causes vibrations that initiate nerve impulses which travel to the cochlear nerve and then to the brain. – Pitch is determined by varying wave frequencies that are detected by different parts of the spiral organ. – Volume is determined by the amplitude of sound waves. 6 14.5 Sense of Hearing The inner ear: Hearing Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. semicircular canals oval window cochlea stapes round window vestibular canal cochlear canal tympanic canal cochlear nerve Cochlea cross section tectorial membrane stereocilia basilar membrane hair cell cochlear nerve tympanic canal Spiral organ Figure 14.13 How the spiral organ (organ of Corti) translates sound waves into nerve signals. Stereocilia (stereocilia): © P. Motta/SPL/ Photo Researchers, Inc. 2 µm 7 14.5 Sense of Hearing The inner ear: The spiral organ Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. tectorial membrane stereocilia basilar membrane hair cell cochlear nerve tympanic canal Spiral organ Figure 14.13 How the spiral organ (organ of Corti) translates sound waves into nerve signals. 8 14.6 Sense of Equilibrium The inner ear: Semicircular canals and vestibule • Detects angular movement (_____________ ____________) – Depends on hair cells at the base of each semicircular canal (ampulla) • Detects movement of the head in the vertical and horizontal planes (gravitational equilibrium) – Depends on hair cells in the utricle and saccule 9 14.6 Sense of Equilibrium The inner ear: Balance Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. semicircular canals receptor in ampulla endolymph Vestibular nerve ampullae cochlea utricle saccule endolymph cupula otoliths stereocilia otolithic membrane Hair cell hair cell Supporting cell supporting cell vestibular nerve Vestibular nerve flow of endolymph Flow of otolithic membrane Figure 14.14 The mechanoreceptors of the inner ear and the sense of balance. a. Rotational equilibrium: receptors in ampullae of semicircular canal kinocilium stereocilia b. Gravitational equilibrium: receptors in utricle and saccule of vestibule 10 14.6 Sense of Equilibrium Noise pollution • Loud noises (>85 decibels) or chronic noise can damage inner ear cells. • Environmental noise can cause mental health issues such as inability to concentrate, an increase in irritability, and anxiety. • Noise can cause loss of sleep and productivity, and can lead to anxiety. • What should be done about noise pollution? 11