Which cells are photoreceptors

Two types of photoreceptors reside in the retina : cones and rods. The cones are responsible for daytime vision, while the rods respond under dark conditions. The cones come in three varieties: L, M, and S types for long, middle, and short wavelength. Each cone type responds to a different portion of the visible spectrum, allowing for color vision. Rods have a spectral sensitivity that differs from the cones. Photoreceptors are specialized cells for detecting light.

They are composed of the outer nuclear layer that contains the cell nuclei, the inner segment that houses the cell machinery, and the outer segment that contains photosensitive pigment. The outer segment of a rod has discrete disks saturated with rhodopsin molecules, while the outer segment of a cone contains similar photosensitive molecules in a series of folds.

The outer segment absorbs photons, which initiates an electrochemical transmission through the cells and retinal nerve fibers, up into the brain. At a certain distance, the blue line will not look broken! Did you know? Why can't you see very well when you first go into a darkened room like a movie theater? When you first enter the movie theater, the cones in your retina are working and the rods are not yet activated.

Cones need a lot of light to work properly; rods need less light to work, but they need about minutes to take over for the cones. After minutes in the dark, the rods do work, but you cannot see colors very well because the rods do not provide any color information. The cones, which do provide color information, need more light, but do not work well in the dark. After the movie is over and you leave the theater, everything looks very bright and it is hard to see for a minute or two.

This is because the rods become "saturated" and stop working in these bright conditions. It takes a few minutes for the cones to begin to function again, and for normal vision to be restored. A complete lesson plan on the eye and its connections - teacher and student guides available. Also, try some experiments to test your sense of sight and take a short, interactive quiz about the eye and sight.

Find out more about blind spots , vision , the retina and photoreceptors. The Retina The retina is the back part of the eye that contains the cells that respond to light.

Stare at the "g" in the word "light" in middle of the following sentence: "Your vision is best when light falls on the fovea. To find your blind spot, look at the image below or draw it on a piece of paper: Close your left eye. Here is another image that will help you find your blind spot. A typology of photoreceptor gene expression patterns in the mouse.

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