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. Divisions of the ear: Outer ear 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. Divisions of the ear: Middle ear 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

Following the sound wave 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 oval window malleus vestibule vestibular nerve pinna cochlear nerve tympanic membrane cochlea auditory canal temporal bone round window auditory tube Figure 14.12 The three divisions of the human ear.

3. Divisions of the ear: Inner ear 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

The inner ear: The cochlea 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.

(stereocilia): © P. Motta/SPL/ Photo Researchers, Inc. 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 tympanic canal cochlear nerve Spiral organ Figure 14.13 How the spiral organ (organ of Corti) translates sound waves into nerve signals. Stereocilia 2 µm (stereocilia): © P. Motta/SPL/ Photo Researchers, Inc.

The inner ear: The spiral organ 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 tympanic canal cochlear nerve Spiral organ Figure 14.13 How the spiral organ (organ of Corti) translates sound waves into nerve signals.

The inner ear: Semicircular canals and vestibule 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

The inner ear: Balance 14.6 Sense of Equilibrium Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. receptor in ampulla endolymph semicircular canals Vestibular nerve ampullae cochlea utricle saccule endolymph cupula otoliths stereocilia Hair cell otolithic membrane 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. kinocilium stereocilia a. Rotational equilibrium: receptors in ampullae of semicircular canal b. Gravitational equilibrium: receptors in utricle and saccule of vestibule

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?