Special Senses: The Ear and Hearing Ch. 8b

The Ear Slide 8.20 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Houses two senses  Hearing  Equilibrium (balance)  Receptors are mechanoreceptors  Different organs house receptors for each sense

Anatomy of the Ear Slide 8.21 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  The ear is divided into three areas  Outer (external) ear  Middle ear  Inner ear Figure 8.12

The External Ear Slide 8.22 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Involved in hearing only  Structures of the external ear  Pinna (auricle)  External auditory canal Figure 8.12

The External Auditory Canal Slide 8.23 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Narrow chamber in the temporal bone  Lined with skin  Ceruminous (wax) glands are present  Ends at the tympanic membrane

The Middle Ear or Tympanic Cavity Slide 8.24a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Air-filled cavity within the temporal bone  Only involved in the sense of hearing

The Middle Ear or Tympanic Cavity Slide 8.24b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Two tubes are associated with the inner ear  The opening from the auditory canal is covered by the tympanic membrane  The auditory tube connecting the middle ear with the throat  Allows for equalizing pressure during yawning or swallowing  This tube is otherwise collapsed

Bones of the Tympanic Cavity Slide 8.25a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Three bones span the cavity  Malleus (hammer)  Incus (anvil)  Stapes (stirrip) Figure 8.12

Bones of the Tympanic Cavity Slide 8.25b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Vibrations from eardrum move the malleus  These bones transfer sound to the inner ear Figure 8.12

Inner Ear or Bony Labyrinth Slide 8.26a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Includes sense organs for hearing and balance  Filled with perilymph Figure 8.12

Inner Ear or Bony Labyrinth Slide 8.26b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  A maze of bony chambers within the temporal bone  Cochlea  Vestibule  Semicircular canals Figure 8.12

Quick Quiz 1 of 3 What is the name of the part of the ear that you can see on the side of your head? What is name of the structure that separates the external auditory canal from the middle ear?

Organs of Hearing Slide 8.27a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Organ of Corti  Located within the cochlea in the inner ear  Receptors = hair cells on the basilar membrane  Gel-like tectorial membrane is capable of bending hair cells  Cochlear nerve attached to hair cells transmits nerve impulses to auditory cortex on temporal lobe

Organs of Hearing Slide 8.27b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.13

Mechanisms of Hearing Slide 8.28 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Vibrations from sound waves move tectorial membrane  Hair cells are bent by the membrane  An action potential starts in the cochlear nerve  Continued stimulation can lead to adaptation

Mechanisms of Hearing Slide 8.29 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.14

Quick Quiz 2 of 3 What is the organ in the inner ear called that is responsible for hearing? Explain in simple terms how the organ of corti works

A&P Revealed Hearing

Organs of Equilibrium Slide 8.30a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Receptor cells are in two structures  Vestibule  Semicircular canals Figure 8.16a, b

Organs of Equilibrium Slide 8.30b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Equilibrium has two functional parts  Static equilibrium  Dynamic equilibrium Figure 8.16a, b

Static Equilibrium Slide 8.31 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Maculae – receptors in the vestibule  Report on the position of the head  Send information via the vestibular nerve  Anatomy of the maculae  Hair cells are embedded in the otolithic membrane  Otoliths (tiny stones) float in a gel around the hair cells  Movements cause otoliths to bend the hair cells

Function of Maculae Slide 8.32 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 8.15

Dynamic Equilibrium Slide 8.33a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Crista ampullaris – receptors in the semicircular canals  Tuft of hair cells  Cupula (gelatinous cap) covers the hair cells Figure 8.16c

Dynamic Equilibrium Slide 8.33b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Action of angular head movements  The cupula stimulates the hair cells  An impulse is sent via the vestibular nerve to the cerebellum Figure 8.16c

Quick Quiz 3 of 3 Where are the receptor cells that sense body position and movement located? What happens to the hair cells to stimulate a nerve impulse?