2.86 Describe the structure and function of the eye as a receptor, 2.87 understand the function of the eye in focusing near and distant objects, and in responding to changes in light intensity

Structure:

1. CORNEA
2. EPITHELIUM
3. IRIS
4. PUPIL
5. RETINA
6. SCLERA
7. LENS

Sight is the transmission of light signals through nerve endings to the brain, which interprets the signals and produces visions of what is seen.

- Light enters the eye first through the cornea
- The pupil is the opening that controls how much light passes from the cornea to the lens. The iris, the colored portion of the eye, is actually two sets of muscle fibers that control the size of the pupil.
- Light travels from the lens through a chamber filled with vitreous humor, a semi-solid that helps the eye keep its shape.
- The retina is the back of the inside of the eye and contains light receptors. The receptors are nerve endings with a direct link to the brain via the optic nerve.
- Receptors in the eye consist of rods and cones. Rods detect light regardless of wavelength and help the brain determine light intensity, whether it is bright or dim.
- Cones are only active in bright light and are particular to red, blue, or green. Each type of cone detects a particular light wavelength.