Chapter 15 - The Special Senses - Review Questions - Page 589: 31

Rods and cones are the light receptor cells of the retina of the eye. They differ both in structure and function. The following are some of the functional differences: 1. Light sensitivity: Rods are very light-sensitive Cones are less sensitive 2. Rods respond better in dim light Cones require bright light for optimal response 3 Rods and cones are the light receptor cells of the retina of the eye. They differ in structure but more importantly they perform different visual functions. The most important issues regarding functions are sensitivity to light, color vision, and facilitation of resolution of details in a sciene or image Sensitivity to light: Rods are more light sensitive than cones and are the receptors most suitable for night vision and for viewing with peripheral lighting. They are the night vision receptors Color Perception While rods have only one color pigment(purple), cones have three color pigments --red, green and blue. Furthermore, cones can combine aspects of these spectra to enable reception of several other colors like orange, yellow, and purple Resolution and details Sharpest focus of objects and greatest resolution of details are obtained by viewing from the fovea centralis of the macula lutea. There are fewer cones to rods in the retina overall. In the macula lutea the light receptors are mostly cones, and all the receptors in the fovea centralis are cones. The cones of the fovea centralis provide the highest visual acuity and the best resolution of details. Each rod, in general, is connected to several ganglion cells ;the result is that rod viewing produces more diffuse images, poorer resolution, and lower visual acuity. Cones, on the other hand, are adapted for bright light vision. They are high descrimination receptors that enable sharp focusing and high adnd detailed resolution. Conesare the color vision receptors.

The following are some of the functional difference between rods and cones: 1. Rods are more light sensitive than cones and respond for optimal functioning 2. Rods are more suitable for night vision Cones function better in full daylight 3. Rods are better for peripheral viewing Cones require direct focused lighting 4. Rods are most useful for non-color viewing Cones have three color pigments( red, green, blue); they combine these color spectra to enable viewing of orange, yellow and purple objects. 5. Rods allow only low acuity viewing Cones, of the fovea facilitate sharp focus and high acuity viewing.