Rods and Cones

Rods and cones are amazing cells that allow the eye to function as it does. They are each a specific type of cell called photoreceptors. Both cells are located in the retina of the eye. These cells both are composed of epithelial tissue. While both structures are very similar, they each have a few distinguishing features. As they sound, the names of the cells describe how they look like. Rods are long and skinny looking, while cones look like an upside down cone with the point sticking up. Both cells contain disk-like disks which contain molecules that allow the light photons to be absorbed. In rods these disks are closed, unlike cones where the disks are partially opened and exposed to the liquid around it. Both contain the typical organelles of an eukaryotic cell such as a nucleus and mitochondria. It also contains an axon, which acts to send signals to neurons that eventually makes its way all the way to the brain to be processed. Also in birds or reptiles, these receptors may have oil droplets, which enhance their color vision.

There are many more rods in the retina than there are cones. The proportion of rods to cones is about 120 million rods to the 6-7 million cones. Rods are more sensitive than cones, but are not sensitive to colors, as cones are. Rods are extremely sensitive to light and are better motion sensors. Rods primarily are used in the peripheral vision, so the eye is more sensitive to light from the sides. Rods take a longer time to adapt to a new environment unlike cones. It takes roughly 30 minutes for the rods to adjust to darkness and function correctly. Cones are used to see the many different colors of the rainbow. They are separated into different types that each sense different colors. For example, there are blue cones, red cones, and green cones. Each of them respectively senses a different color.