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Sensory System

Vision

What are the different types of cone cells in humans?

Color perception depends on cones. Humans have three types of cones: blue, green, and red. Each contains a slightly different photopigment. Although the retinal portion of the pigment molecule is the same as in rhodopsin, the opsin protein differs slightly in each type of photoreceptor. Each type of cone responds to light within a range of wavelengths but is named for the ability of its pigment to absorb a wavelength more strongly than the other cones. Red light, for example, can be absorbed by all three types of cones, but those cones most sensitive to red act as red receptors. By comparing the relative responses of the three types of cones, the brain can detect colors of intermediate wavelengths. There will always be a dominant cone sending the electrical color-coded impulse to the brain, but the other two color cones will also be stimulated to some degree, even if it is a faint spark. These various and unlimited combinations are what make possible the million of shades of color we see.



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