Special Senses: The Ear and Hearing Ch. 8b. The Ear Slide 8.20 Copyright © 2003 Pearson Education,...

Special Senses: The Ear and Hearing

Ch. 8b

The EarThe Ear

Slide 8.20Copyright © 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 EarAnatomy of the Ear

Slide 8.21Copyright © 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 EarThe External Ear

Slide 8.22Copyright © 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 CanalThe External Auditory Canal

Slide 8.23Copyright © 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 CavityThe Middle Ear or Tympanic Cavity

Slide 8.24a

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Air-filled cavity within the temporal bone

Only involved in the sense of hearing

The Middle Ear or Tympanic CavityThe Middle Ear or Tympanic Cavity

Slide 8.24b

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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 CavityBones of the Tympanic Cavity

Slide 8.25a

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Three bones span the cavity

Malleus (hammer)

Incus (anvil)

Stapes (stirrip)

Figure 8.12

Bones of the Tympanic CavityBones of the Tympanic Cavity

Slide 8.25b

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Vibrations from eardrum move the malleus

These bones transfer sound to the inner ear

Figure 8.12

Inner Ear or Bony LabyrinthInner Ear or Bony Labyrinth

Slide 8.26a

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Includes sense organs for hearing and balance

Filled with perilymph

Figure 8.12

Inner Ear or Bony LabyrinthInner Ear or Bony Labyrinth

Slide 8.26b

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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 HearingOrgans of Hearing

Slide 8.27a

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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 HearingOrgans of Hearing

Slide 8.27b

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Figure 8.13

Mechanisms of HearingMechanisms of Hearing

Slide 8.28Copyright © 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 HearingMechanisms of Hearing

Slide 8.29Copyright © 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 EquilibriumOrgans of Equilibrium

Slide 8.30a

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Receptor cells are in two structures

Vestibule

Semicircular canals

Figure 8.16a, b

Organs of EquilibriumOrgans of Equilibrium

Slide 8.30b

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Equilibrium has two functional parts

Static equilibrium

Dynamic equilibrium

Figure 8.16a, b

Static EquilibriumStatic Equilibrium

Slide 8.31Copyright © 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 MaculaeFunction of Maculae

Slide 8.32Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Figure 8.15

Dynamic EquilibriumDynamic Equilibrium

Slide 8.33a

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Crista ampullaris – receptors in the semicircular canals

Tuft of hair cells

Cupula (gelatinous cap) covers the hair cells

Figure 8.16c

Dynamic EquilibriumDynamic Equilibrium

Slide 8.33b

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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?