Transcript Ch 13 PNS, Part III (Hearing)

Lend me your ear.
Ch 13 PNS, Part III (Hearing)
Learning Objectives
1. Be able to identify the structures of the ear (all)
2. Discuss the bones of the middle ear
3. Explain how we hear
4. Explain the mechanisms of balance & equilibrium in
the ear
Read 469 – 480 on Ears, Hearing, and Balance. Review all chapter notes.
CSI: Can You Spot the Ear?
• http://video.google.com/videoplay?docid=7933116988114927395&total=36&start=10
&num=10&so=0&type=search&plindex=9
More info please >
Vacanti Mouse
• It might look like the work of a mad scientist but the Vacanti mouse
with what appears to be a human ear growing on its back is the real
deal. You won't find this mouse at the circus; it was created at the
University of Massachusetts in 1997. Dr. Charles Vacanti developed
the mouse by putting a mold resembling the shape of a human ear
onto its back.
• Dr. Vacanti is helping researchers fine tune a technology that will let
them re-grow ears and noses for people. It was a plastic surgeon
who suggested growing ears on mice after seeing kids who were
born with out ears or who'd had them torn off in accidents.
• The 'ear' mold was made from special fibers that are
biodegradable, much like dissolving stitches that doctors often use.
Before the mold is implanted into the back of a hairless mouse, it is
covered with cow cartilage cells. Blood from the mouse helps the
cartilage cells grow and eventually replace the fibers. Researchers
say that the rodent could have the ear removed and still remain
alive and healthy.
Practice Activity: How Well Do You
Know The Parts of the Ear?
• See handout
Hearing and Balance Pgs 469 - 480
• The three parts of the ear are the ______,
______, and ________ ear
• The outer and middle ear are involved with
_______
• The inner ear functions in both hearing
and ________
• Receptors for hearing and balance:
– Respond to separate stimuli
– Are activated independently
Outer, Middle and Inner Ear
Label or bracket the three regions of the ear: outer, middle and inner on your
diagram.
Outer Ear
• The auricle or ______ is composed of:
– The helix (rim)
– The lobule (earlobe)
• External auditory canal
– Short, curved tube filled with ceruminous or ____
glands
• Tympanic membrane or ________
– Thin connective tissue membrane that vibrates in
response to sound
– Transfers sound energy to the middle ear ossicles
– Boundary between outer and middle ears
Middle Ear
• A small air-filled mucosa-lined ______
– Flanked laterally by the ________
– Flanked medially by the oval and round
windows
• Pharyngotympanic tube – connects the
middle ear to the nasopharynx
– _______ ________ in the middle ear cavity
with the external air pressure
Middle Ear
Bones of the
Middle Ear
• The tympanic cavity contains three small
bones: the ______,______, and ______.
• Transmit vibratory motion of the eardrum
to the oval window
These bones are formally named the "malleus", the
"incus", and the "stapes", but they are more
commonly known as the "hammer", the "anvil" and
the "stirrup".
Porpoise inner ear bones
Inner Ear
• ______ labyrinth
– Tortuous channels worming their way through the
temporal bone
– Contains the _________, the __________, and the
_________________
– Filled with fluid called _________
• __________ labyrinth
– Series of membranous sacs within the bony labyrinth
– Filled with a potassium-rich fluid
Vestibule
• The central egg-shaped cavity of the bony
labyrinth
• Suspended in its perilymph are two sacs: the
saccule and utricle
• The saccule extends into the cochlea
• The utricle extends into the semicircular canals
• These sacs:
– House equilibrium receptors called maculae
– Respond to gravity and changes in the position of the
head
Semicircular Canals
• Three canals that each define two-thirds of
a circle and lie in the three planes of space
• Membranous semicircular ducts line each
canal and communicate with the utricle
• The ampulla is the swollen end of each
canal and it houses equilibrium receptors
in a region called the crista ampullaris
• These receptors respond to angular
movements of the head
Cochlea
• A spiral, conical, bony chamber that:
– Extends from the anterior vestibule
– Coils around a bony pillar called the modiolus
– Contains the cochlear duct, which ends at the
cochlear apex
– Contains the organ of Corti (hearing receptor)
Internal Ear Anatomy
Instructions: Label the malleus, incus, stapes, eardrum, cochlea, vestibule, and
semicircular canals on your practice diagram now. Pg 470
How Do We Hear?
• Sound vibrations beat against the eardrum
• The eardrum pushes against the ossicles,
which presses fluid in the inner ear against
the oval and round windows
– This movement sets up shearing forces that
pull on hair cells
– Moving hair cells stimulates the cochlear
nerve that sends impulses to the brain
Hearing & Balance
• http://video.google.com/videoplay?docid=4811948101588376689&q=balance+%2B
+middle+ear&total=26&start=0&num=10&
so=0&type=search&plindex=0
Balance & Equilibrium
• Vestibular apparatus – __________
in the semicircular canals and vestibule
– Maintains our _________________ in space
– Vestibular receptors monitor static equilibrium
– Semicircular canal receptors monitor dynamic
equilibrium
Balance & Equilibrium continued
• Maculae are the sensory receptors for static
equilibrium
– Contain supporting cells and hair cells
• Otolithic membrane is a jellylike mass studded
with tiny CaCO3 stones called _________
• Utricular hairs respond to ________movement
• Saccular hairs respond to _______ movement