Download Ears - science105

PowerPoint® Lecture Slide Presentation
by Patty Bostwick-Taylor,
Florence-Darlington Technical College
Ears and
Hearing
8
PART B
Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings
Ears Med Terms
1. Cochlea – snail
6. Oto – ear
2. itis - inflammation
7. Peri – covering
3. Labyrinth – maze
8. Semi - half
4. Lymph - fluid
9. Tympan – drum
5. Oss - bone
10. Vestibul - chamber
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Anatomy of the Ear
 The ear is divided into three areas
 External (outer) ear
 Middle ear (tympanic cavity)
 Inner ear (bony labyrinth)
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The Ear
 Houses two senses
 Hearing
 Equilibrium (balance)
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Anatomy of the Ear
Figure 8.12
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The External Ear
 Involved in hearing only
 Structures of the external ear
 Auricle (pinna)
 Funnels sound waves
 External acoustic meatus (auditory canal)
 Narrow chamber in the temporal bone
 Lined with skin and ceruminous (wax)
glands
 Ends at the tympanic membrane
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Why wax?
 The actual wax that is observed is the coating
of the inside of your ear in order to protect it
from things entering the ear canal. Ear wax is
produced by a gland that is inside your ear, to
help keep away dirt, bugs, and even germs.
When your ears are not cleaned for a long
time, the wax eventually just dries up and falls
out in tiny, flaky bundles that you don't even
realize.
 ~D.W.
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The Middle Ear (Tympanic Cavity)
 Air-filled cavity within the temporal bone
 Only involved in the sense of hearing
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The Middle Ear (Tympanic Cavity)
 The opening from the auditory canal is covered by
the tympanic membrane
 Tympanic Membrane - vibrates in response to
pressure changes
 The auditory tube connects the middle ear with
the throat
 Allows for equalizing pressure during yawning
or swallowing
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Anatomy of the Ear
Figure 8.12
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The auditory tube
 If pressure outside is greater than inside, ears will
“pop”
 Chewing gum can help equalize pressure
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Ear Infections (Otitis media)
 Don’t close nostrils when blowing nose, can force
debris into the ears causing infection of the
middle ear (otitis media)
 Frequent ear infections can receive “tubes” for
drainage
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Bones of the Middle Ear (Tympanic Cavity)
 Three bones (ossicles) span the cavity
 Malleus (hammer)
 Incus (anvil)
 Stapes (stirrip)
 Function
 Vibrations from eardrum move the Malleus 
Incus  Stapes  inner ear
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Anatomy of the Ear
Figure 8.12
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Inner Ear or Bony Labyrinth
 Vibrations enter through the oval window from the
Stapes
 Vibrations move perilymph fluid in:
 Semicircular canals
 Sensing equilibrium
 Vestibule
 Connects semicircular canals to cochlea
 Cochlea
 Contains the hairs for hearing senses
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Cochlea
 Hair Cells
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A sense of hearing
 Cell membrane protein channels open in
response to changes in frequencies
 Allow Ca+2 ions to flow into the cells
 Triggers neurotransmitter release
 Sends signal through vestibulocochlear nerve to
the brain
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Mechanism of Hearing
Figure 8.16a
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Anatomy of the Ear
Figure 8.12
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Decibels (dB) - measure sound intensity
 0 dB - least perceptible by humans
 40 dB - whispering
 60-70 dB - normal conversation
 80 dB - heavy traffic
 90 dB - above this can damage hearing receptors
 120 dB - Rock concert
 140 dB - Jet plane takeoff
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Partial or complete hearing loss
 Eardrum can harden as a result of disease
 Eardrum can tear or perforate due to disease or
injury
 Loud sounds, tumors, brain damage or drug use
can damage nerve pathways
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Organs of Equilibrium
 Equilibrium receptors of the inner ear are called
the vestibular apparatus
 Vestibular apparatus has two functional parts
 Static equilibrium
 Dynamic equilibrium
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Organs of Equilibrium
Figure 8.14a–b
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Static Equilibrium
 Maculae—receptors in the vestibule
 Report on the position of the head
 Send information via the vestibular nerve
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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
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Structure and Function of Maculae
Figure 8.13a
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Structure and Function of Maculae
Figure 8.13b
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Dynamic Equilibrium
 Crista ampullaris—receptors in the semicircular
canals
 Tuft of hair cells
 Cupula (gelatinous cap) covers the hair cells
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Dynamic Equilibrium
Figure 8.14c
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Dynamic Equilibrium
 Action of angular head movements
 The cupula stimulates the hair cells
 An impulse is sent via the vestibular nerve to
the cerebellum
 The brain interprets the signals and “predicts”
the consequences
 Signals to the appropriate skeletal muscles
and allows the cerebellum to maintain balance
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Other Sensory Structures
 Maintaining equilibrium is a combined effort:
 Hair Cells
 Receptors in your neck
 Eyes
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Motion Sickness
 Abnormal or irregular body movements that
disturb the organs of equilibrium
 Nausea, vomiting, dizziness or headache
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