CHAPTER FIFTEEN LESSON NINE EYES & EARS

OBJECTIVES DESCRIBE THE FUNCTION OF EYES AND EARS. DESCRIBE THREE NONINFECTIOUS DISEASES OF THE EYES AND EARS.

BELLRINGER LIST THREE THINGS YOU WOULD MISS MOST IF YOU COULD NOT SEE. LIST ANOTHER TEN THINGS YOU WOULD MISS MOST IF YOU COULD NOT HEAR.

ESSENTIAL QUESTION HOW DO YOUR EYES AND EARS GIVE YOU INFORMATION ABOUT YOUR WORLD?

DEFINITIONS YOUR EARS ARE SENSORY ORGANS USED FOR HEARING. YOUR EYES ARE SENSORY ORGANS THAT SEND INFORMATION FROM THE WORLD AROUND YOU TO YOUR BRAIN. LIGHT PASSES THROUGH THE CORNEA, THE PUPIL, AND THE LENS OF YOUR EYE. THE LENS FOCUSES LIGHT ON THE RETINA. THE CELLS OF THE RETINA SEND ELECTRICAL IMPULSES TO YOUR BRAIN. YOUR BRAIN CHANGES THESE ELECTRICAL IMPULSES INTO IMAGES. YOUR EARS ARE SENSORY ORGANS USED FOR HEARING. SOUND WAVES THAT REACH THE OUTER EAR ARE FUNNELED TOWARD THE EARDRUM AND MAKE THE EARDRUM VIBRATE. THESE VIBRATIONS TRAVEL THROUGH THE THREE SMALL BONES OF THE MIDDLE EAR—THE HAMMER, THE ANVIL, AND THE STIRRUP—TO THE INNER EAR. THE INNER EAR CONVERTS THE VIBRATIONS INTO ELECTRICAL IMPULSES, WHICH GO TO THE BRAIN.

DEFINITIONS

DEFINITIONS EYES A CATARACT IS A CLOUDING OF THE NATURAL LENS OF THE EYE. GLAUCOMA IS A DISEASE THAT CAUSES HIGH PRESSURE IN THE FLUID INSIDE THE EYE. EARS DEAFNESS IS THE PARTIAL OR TOTAL LOSS OF THE ABILITY TO HEAR. THERE ARE MANY LEVELS OF HEARING LOSS, FROM MILD LOSS TO TOTAL DEAFNESS.