1. Process of Eyesight and Hearing

2. Eye Structure Layers Eye composed of three layers
Outside Layer: Sclera – white of the eye
Muscles attached to the sclera allow the eye to move
Front of the sclera curves outward to form the cornea – transparent and permits light into the eye
Optic Nerve – transmits visual information to the brain
Conjunctiva – thin, moist membrane / covers front part of sclera and inside the eyelid

3. Eye Structure Layers Middle Layer – Choroid
Choroid – mostly blood vessels, just inside the sclera and ends at the front of the eye in two structures:
Iris – colored disk with the opening in the center / determines color of eye
Pupil – opening of the iris / determines amount of light entering the eye from the cornea
Bright light – muscles of the iris contract, causing the pupil to narrow and let in less light
Dim light – muscle fibers relax, pupil becomes larger, letting more light in
Ciliary Body – produces water fluid between cornea and the lens
Small muscles in the ciliary body contract or relax to change the shape of the lens
Lens – behind the iris, ciliary muscles help lens to focus on objects at various distances

4. Eye Structure Layers Inner Layer – Retina
Retina – light-sensing portion of eye, containing thousands of light receiving cells and nerve cells
Two types of light receiving cells:
Rods – dim light, allow to see black and white
Cones – bright light, enable you to see color
Rods and cones convert images focused on the retina to nerve signals, which are transmitted to the brain by the optic nerve

5. How Vision Occurs
Light passes through the cornea, the lens, and vitreous humor before reaching the retina
Light receptor cells (Rods and Cones) convert the light images to signals traveling through the optic nerve to be interpreted in the brain

6. Structure of the Ear Outer Ear
Ear lobes and exposed portions of the ear funnel sound waves into the ear canal
End of the ear canal is the eardrum
Eardrum vibrates when sound waves strike it

7. Structure of the Ear Middle Ear
Eardrum sends vibrations into the middle ear
Vibrations are processed by three tiny bones called the hammer (malleus), anvil (incus), and stirrup (stapes)
These bones magnify gentle sounds and soften loud ones

8. Structure of the Ear Inner Ear
Vibrations from the bones in the middle ear transmit sound vibrations to the cochlea
Cochlea – hollow, fluid-filled, coiled tube with special vibration sensing cells
These vibration cells send out nerve signals that travel through the auditory nerve to the brain, where they are interpreted as sound