Talk:Photoreceptor cell/July 2006
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Photoreceptor cells are found in the retina of the eye and are responsible for transducing, or converting, light into nerve signals that can be ultimately transmitted to the brain via the optic nerve. In vertebrates, there are two types of photoreceptor cells: rods and cones. Cones are adapted to detect colors, and function well in bright light; rods are more sensitive, but do not detect color well, being adapted for low light. The human retina contains about 125 million rod cells and 6 million cone cells. The number and ratio of rods to cones varies among animals, dependant on whether the animal is primarily diurnal or nocturnal. Certain owls have a tremendous number of rods in their retinas ā the eyes of the tawny owl are approximately 100 times more sensitive at night than those of humans.