Transcript Your Eyes

Section 14.3 Your Eyes and Ears
Your Eyes and Ears
Objectives
Explain how your eyes allow you to see.
Identify two ways to keep your
eyes healthy.
Explain how your ears allow you to hear and
maintain your balance.
Identify ways to keep your
ears healthy.
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Section 14.3 Your Eyes and Ears
Dear Advice Line,
One of my friends likes to play loud music when I am
at his house. Sometimes when I leave, my ears are
ringing and I have trouble hearing for several hours.
I’ve asked him to lower the music, but he just laughs
at me. I don’t want to stop hanging out with him.
What should I do?
Write a response to this teen to help solve
the problem.
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Section 14.3 Your Eyes and Ears
Your Eyes
• The eyes are complex organs that respond to light
by sending impulses.
• Your brain then interprets the impulses as images.
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Section 14.3 Your Eyes and Ears
How Light Enters Your Eye
• The cornea (KAWR nee uh) is the clear tissue that
covers the front of the eye.
• The pupil is the opening through which light enters
the eye.
• The iris is a circular structure that surrounds the
pupil and regulates its size.
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Section 14.3 Your Eyes and Ears
How Light Is Focused
• The lens is a flexible structure that focuses light.
• The lens of your eye functions something like the
lens of a camera, which focuses light on
photographic film.
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Section 14.3 Your Eyes and Ears
How You See an Image
• The retina is a layer of cells that lines the back of
the eye.
• When light strikes the rods and cones, nerve
impulses travel through the optic nerves to the brain.
• In the cerebrum, the brain turns the flipped image
right-side up.
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Section 14.3 Your Eyes and Ears
The Eye
Cornea
Retina
Lens
Iris
Optic
nerve
Pupil
Blood
vessels
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Section 14.3 Your Eyes and Ears
Caring for Your Eyes
• It is important to protect your eyes from damage and
to have regular eye exams.
• To protect your eyes from damage wear
protective goggles when you work with harmful
substances or around machinery.
• Wear sunglasses that provide UV protection.
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Section 14.3 Your Eyes and Ears
Detecting Vision Problems
• An optometrist is a professional who provides eye
and vision care, and checks you for vision problems.
• Three common vision problems are
• Nearsightedness People who are nearsighted
can see nearby objects clearly, but not faraway
objects.
• Farsightedness People who are farsighted can
see faraway objects clearly, but nearby objects
appear blurry.
• Astigmatism People with astigmatism have
distorted vision.
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Section 14.3 Your Eyes and Ears
Vision Problems
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Section 14.3 Your Eyes and Ears
Treating Eye Diseases
• Glaucoma is a buildup of pressure in the eye.
• Cataracts The clouding of the eye’s lens is known
as a cataract.
• Detached Retina Aging or an injury to the eye can
cause the retina to separate from the lining of the
eye.
• Macular Degeneration This condition occurs when
cells in the center of the retina break down.
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Section 14.3 Your Eyes and Ears
For: Updates on eye diseases
Click above to go online.
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Section 14.3 Your Eyes and Ears
Treating Eye Infections
• A sty is a painful swelling that occurs when an oil
gland at the base of an eyelash becomes infected.
• Conjunctivitis is an inflammation of the outside layer
of the eye.
• Sties and conjunctivitis can be treated with
prescription medications.
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Section 14.3 Your Eyes and Ears
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Section 14.3 Your Eyes and Ears
Your Ears
• The ears convert sounds into nerve impulses that
your brain interprets.
• In addition, structures in the ear detect the position
and movement of your head.
• Your ears help you to stand upright, walk smoothly,
and adjust your body’s position.
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Section 14.3 Your Eyes and Ears
The Outer Ear
• In the outer ear, the vibrations are channeled into the
ear canal, a narrow cavity that leads to the middle
ear.
• At the end of the ear canal is a thin membrane called
the eardrum.
• The eardrum vibrates when sound vibrations strike it.
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Section 14.3 Your Eyes and Ears
The Middle Ear
• Vibrations from the eardrum pass to the middle ear,
which contains three small bones
• the hammer
• the anvil
• the stirrup
• The vibrating eardrum causes the hammer to vibrate,
which pushes against the anvil, which then moves
the stirrup.
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Section 14.3 Your Eyes and Ears
The Inner Ear
• Vibrations are passed through the oval window to a
hollow, coiled tube filled with fluid called
the cochlea (KAWK lee uh).
• When the cochlear fluid moves, the cells stimulate
impulses in nerves.
• The impulses travel through the auditory nerve to the
brain, where they are interpreted as sound.
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Section 14.3 Your Eyes and Ears
Outer Ear
Sound enters through
the outer ear and
reaches the eardrum.
Middle Ear
Vibrations pass from
the hammer to the
anvil and stirrup.
Hammer Anvil
Ear canal
Stirrup
Eardrum
Auditory
tube
Inner Ear
Vibrations in the
cochlea cause nerve
cells to transmit
signals to the brain.
Semicircular canals
Auditory nerve
Cochlea
Oval window
(behind stirrup)
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Section 14.3 Your Eyes and Ears
The Inner Ear and Balance
• The semicircular canals are structures that send
information to your brain about the movements of
your head.
• Two sacs located behind the canals capture
information about your head’s position.
• When your head moves, the fluid inside the
semicircular canals and sacs causes the “hairs”
to move.
• The movement stimulates nerve cells, which send
impulses to your brain.
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Section 14.3 Your Eyes and Ears
Caring for Your Ears
• Besides keeping your ears clean, you also need to
monitor noise levels.
• You should see a doctor if you experience ear pain
or hearing difficulties.
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Section 14.3 Your Eyes and Ears
Ear Care
• Use a wet washcloth to clean your outer ear and the
front part of your ear canal.
• Dry your ears thoroughly after you wash them.
• Never insert a cotton-tipped swab or any other object
into your ear canal.
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Section 14.3 Your Eyes and Ears
Monitoring Noise Levels
• Partial hearing loss or deafness can result from
damage to nerves or to the vibration-sensing cells in
the cochlea.
• The intensity, or loudness, of sound is measured in
units called decibels (DES uh bulz).
• To avoid hearing damage
• Keep your television and stereo low enough that
you can comfortably hear a person speaking at a
normal level.
• Never turn the music player up to more than 60
percent of its potential volume.
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Section 14.3 Your Eyes and Ears
Decibel Levels of Daily Life
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Section 14.3 Your Eyes and Ears
Treating Ear Infections
• Bacterial infections of the middle ear can sometimes
result in some hearing loss.
• A middle-ear infection may cause the eardrum to
break, or rupture.
• Scar tissue makes the eardrum less flexible and less
able to transmit sound.
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Section 14.3 Your Eyes and Ears
Treating Hearing Problems
• Some types of hearing loss can be inherited.
• Diseases, high fevers, and large doses of medication
can also cause hearing loss.
• People with hearing problems see an
audiologist (aw dee AHL uh jist) .
• Audiologists are professionals who are trained to
evaluate hearing and treat hearing loss.
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Section 14.3 Your Eyes and Ears
Vocabulary
cornea
pupil
iris
Clear tissue that covers the front of the eye.
The opening through which light enters the eye.
The structure that surrounds the pupil and
regulates the amount of light that enters the eye.
lens
A flexible structure in the eye that focuses light
on the retina.
retina
A layer of light-sensing cells that lines the back
of the eye.
optometrist
A professional trained to provide eye and vision
care.
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Section 14.3 Your Eyes and Ears
Vocabulary
eardrum
The membrane at the end of the ear canal that
passes vibrations to the middle ear.
cochlea
A coiled, fluid-filled tube in the inner ear that
contains cells that sense sound vibrations.
semicircular
canals
audiologist
Structures in the inner ear that help
control balance.
A professional who evaluates hearing and treats
hearing loss.
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Section 14.3 Your Eyes and Ears
QuickTake Quiz
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Section 14.3 Your Eyes and Ears
End of Section 14.3
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