special senses: the ear and hearing ch. 8b. the ear slide 8.20 copyright © 2003 pearson education,...
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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
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 CavityThe 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 CavityBones 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 CavityBones 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 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
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 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
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
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
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
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
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 EquilibriumDynamic 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?