Normalised absorption spectra of human cone (S,M,L) and rod (R) cells

Trichromatic color vision is the ability of humans and some other animals to see different colors, mediated by interactions among three types of color-sensing cone cells. Each of the three types of cone in the retina of the eye contains a different type of photosensitive pigment called retinal, which is composed of a transmembrane protein called opsin and a light-sensitive protein called 11-cis retinal. Each different pigment is especially sensitive to a certain wavelength of light (that is, the pigment is most likely to produce a cellular response when it is hit by a photon with the specific wavelength to which that pigment is most sensitive). The three types of cones are L, M, and S, which have pigments that respond best to light of long (especially 560 nm), medium (530 nm), and short (420 nm) wavelengths respectively (Kandel et al., 2000). Spectral absorption curves of the short (S), medium (M) and long (L) wavelength pigments in human cone and rod (R) cells. ... Spectral absorption curves of the short (S), medium (M) and long (L) wavelength pigments in human cone and rod (R) cells. ... Normalised absoption spectra of human rod (R) and cone (S,M,L) cells. ... Color is an important part of the visual arts. ... Normalised absorption spectra of human cone (S,M,L) and rod (R) cells Cone cells, or cones, are cells in the retina of the eye which only function in relatively bright light. ... Human eye cross-sectional view. ... This article refers to the sight organ. ... The Retinenes (Retinene1 and Retinene2) are chemical derivatives of the dietary supplement vitamin A (see retinol) formed through oxidation reactions. ... A transmembrane protein is an integral membrane protein that spans from the internal to the external surface of the biological membrane or lipid bilayer in which it is embedded. ... A rhodopsin molecule in the cell membrane. ... The wavelength is the distance between repeating units of a wave pattern. ... Prism splitting light Light is electromagnetic radiation with a wavelength that is visible to the eye (visible light) or, in a technical or scientific setting, electromagnetic radiation of any wavelength. ... Cells in culture, stained for keratin (red) and DNA (green) The cell is the structural and functional unit of all living organisms, and are sometimes called the building blocks of life. ... In physics, the photon (from Greek φως phos, meaning light) is a quantum of the electromagnetic field, for instance light. ...

Since the likelihood of response of a given cone varies not only with the wavelength of the light that hits it but also with its intensity, the brain would not be able to discriminate different colors if it had input from only one type of cone. Thus, interactions between at least two types of cone is necessary to produce the ability to perceive color. With at least two types of cones, the brain can compare the signals from each type and determine both the intensity and color of the light. For example, moderate stimulation of a medium-wavelength cone cell could mean that it is being stimulated by very bright red (long-wavelength) light, or by not very intense yellowish-green light. But very bright red light would produce a stronger response from L cones than from M cells, while not very intense yellowish light would produce a stronger response from M cells than from other cells (counterintuitively, a "strong response" here refers to a large hyperpolarization, since rods and cones communicate that they are being stimulated by not firing). Thus trichromatic color vision is accomplished by using combinations of cell responses. Comparative brain sizes In the anatomy of animals, the brain, or encephalon (Greek for in the head), is the higher, supervisory center of the nervous system. ... Hyperpolarization has several meanings: In biology, hyperpolarization occurs when a cells membrane potential dips below its resting level. ...

Color vision is the capacity of an organism or machine to distinguish objects based on the wavelength of the light they reflect or emit. ... Color blindness in humans is the inability to perceive differences between some or all colors that other people can distinguish. ... A monochromat is an organism that is truly color blind. ... A dichromat is an organism for which the perceptual effect of any arbitrarily chosen light from its visible spectrum can be matched by a mixture of no more than two different pure spectral lights. ... A trichromat is an organism for which the perceptual effect of any arbitrarily chosen light from its visible spectrum can be matched by a mixture of no more than three different pure spectral lights. ... A tetrachromat is an organism for which the perceptual effect of any arbitrarily chosen light from its visible spectrum can be matched by a mixture of no more than four different pure spectral lights. ... A pentachromat is an organism for which the perceptual effect of any arbitrarily chosen light from its visible spectrum can be matched by a mixture of no more than five different pure spectral lights. ...

Reference

• Kandel E.R., Schwartz, J.H., Jessell, T.M., Principles of Neural Science, 4th ed., pp.577-580. McGraw-Hill, New York (2000).