Photoreception

photoreception

Biological responses to stimulation by light, most often referring to the mechanism of vision. In one-celled organisms such as the amoeba, the whole cell may be sensitive to light. Earthworms have photoreceptive cells scattered over their bodies to help orient themselves by comparison of light intensities in different directions. Most animals have localized photoreceptors of varying complexity. In humans, photoreception relies on the chemical response of a light-sensitive pigment, rhodopsin, in photoreceptor cells in the retina of the eye. Stimulation of those cells results in a stimulus being conducted toward the nervous system. Humans, like other vertebrates, have two types of photosensitive cells, rod cells and cone cells. Rod cells are responsible for vision when there is little light; cone cells mediate daylight vision and colour. Photoreception also refers to photosynthesis in plants. See also sense.

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Photoreception

The process of absorption of light energy by plants and animals and its utilization for biologically important purposes. In plants photoreception plays an essential role in photosynthesis and an important role in orientation. Photoreception in animals is the initial process in vision. See Photosynthesis, Taxis, Vision

The photoreceptors of animals are highly specialized cells or cell groups which are light-sensitive because they contain pigments which are unstable in the presence of light of appropriate wavelengths. These light-sensitive receptor pigments absorb radiant energy and then undergo physicochemical changes, which lead to the initiation of nerve impulses that are conducted to the central nervous system. See Eye (invertebrate), Eye (vertebrate)