Section 14.3 Your Eyes and Ears Slide 1 of 29 Objectives Explain how your eyes allow you to see. Identify two ways to keep your eyes healthy. Section 14.3

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Section 14.3 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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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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• The eyes are complex organs that respond to light by sending impulses.

Your Eyes

• Your brain then interprets the impulses as images.

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• The cornea (KAWR nee uh) is the clear tissue that covers the front of the eye.

How Light Enters Your 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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• The lens is a flexible structure that focuses light.

How Light Is Focused

• The lens of your eye functions something like the lens of a camera, which focuses light on photographic film.

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• The retina is a layer of cells that lines the back of the eye.

How You See an Image

• 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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Optic nerve

Cornea

Iris

Pupil

LensRetina

Blood vessels

The Eye

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• It is important to protect your eyes from damage and to have regular eye exams.

Caring for Your Eyes

• Wear sunglasses that provide UV protection.

• To protect your eyes from damage wear protective goggles when you work with harmful substances or around machinery.

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• An optometrist is a professional who provides eye and vision care, and checks you for vision problems.

Detecting 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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Vision Problems

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• Glaucoma is a buildup of pressure in the eye.

Treating Eye Diseases

• 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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Click above to go online.

For: Updates on eye diseases

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• A sty is a painful swelling that occurs when an oil gland at the base of an eyelash becomes infected.

Treating Eye Infections

• Conjunctivitis is an inflammation of the outside layer of the eye.

• Sties and conjunctivitis can be treated with prescription medications.

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• The ears convert sounds into nerve impulses that your brain interprets.

Your Ears

• 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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• In the outer ear, the vibrations are channeled into the ear canal, a narrow cavity that leads to the middle ear.

The Outer 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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• Vibrations from the eardrum pass to the middle ear, which contains three small bones

The Middle Ear

• 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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• Vibrations are passed through the oval window to a hollow, coiled tube filled with fluid called the cochlea (KAWK lee uh).

The Inner Ear

• The impulses travel through the auditory nerve to the brain, where they are interpreted as sound.

• When the cochlear fluid moves, the cells stimulate impulses in nerves.

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Hammer Anvil

Ear canal Eardrum

Stirrup

Auditory tube

Oval window(behind stirrup)

CochleaAuditory nerve

Semicircular canals

Outer EarSound enters through the outer ear and reaches the eardrum.

Middle EarVibrations pass from the hammer to the anvil and stirrup.

Inner EarVibrations in the cochlea cause nerve cells to transmit signals to the brain.

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• The semicircular canals are structures that send information to your brain about the movements of your head.

The Inner Ear and Balance

• When your head moves, the fluid inside the semicircular canals and sacs causes the “hairs” to move.

• Two sacs located behind the canals capture information about your head’s position.

• The movement stimulates nerve cells, which send impulses to your brain.

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• Besides keeping your ears clean, you also need to monitor noise levels.

Caring for Your Ears

• You should see a doctor if you experience ear pain or hearing difficulties.

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• Use a wet washcloth to clean your outer ear and the front part of your ear canal.

Ear Care

• 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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• Partial hearing loss or deafness can result from damage to nerves or to the vibration-sensing cells in the cochlea.

Monitoring Noise Levels

• 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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Decibel Levels of Daily Life

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• Bacterial infections of the middle ear can sometimes result in some hearing loss.

Treating Ear Infections

• 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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• Some types of hearing loss can be inherited.

Treating Hearing Problems

• 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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Vocabularycornea Clear tissue that covers the front of the eye.

pupil The opening through which light enters the eye.

iris 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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Vocabularyeardrum 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

Structures in the inner ear that help control balance.

audiologist A professional who evaluates hearing and treats hearing loss.

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QuickTake Quiz

Click to start quiz.

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End of Section 14.3

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Section 14.3 Your Eyes and Ears Slide 1 of 29 Objectives Explain how your eyes allow you to see. Identify two ways to keep your eyes healthy. Section 14.3