Rods and Cones

Rods and Cones
          Rods and cones are the photoreceptors located in eyes, more specifically, retinas, the innermost layer of tissue. There are around 120 million rods located in the human retina, while there are only 6-7 million cones. Rods are more sensitive to light, so they are responsible for vision when there is little to no light. Cones, however, can detect color and shapes and sizes of objects under high light conditions. The ability to detect a shape is called spatial acuity. Therefore, rods have a low spatial acuity while cones have a high spatial acuity. The central fovea is the location of most cones, and only cones are allowed to be there. Rods are more numerous than cones in the periphery of the retina, which provides peripheral vision. Since rods are also better than cones at sensing motion, humans are able to detect motion through peripheral vision. Dimmer objects also appear more visible through peripheral vision because of the rods located in the periphery. These cells are comparable to neurons as their shapes resemble the long shape and they also have the synaptic terminal on the inner side of the cell. Their mitochondria and nucleus are located in the inner segment, and all their organelles are like the eukaryotic cells located in the human nervous system.

http://hyperphysics.phy-astr.gsu.edu/hbase/vision/rodcone.html
http://www.cis.rit.edu/people/faculty/montag/vandplite/pages/chap_9/ch9p1.html
https://faculty.washington.edu/chudler/retina.html


https://upload.wikimedia.org/wikipedia/commons/a/a0/Cone_cell_en.png

http://tridentmedia.org/wp-content/uploads/2015/06/eye-diagram.jpg