Photoreceptor cell

A specialized cell that detects light and converts it into electrical or biochemical signals. In animal vision, photoreceptors transduce photons into changes in membrane voltage or neurotransmitter release.

Phototransduction: The process by which light absorption triggers a biochemical cascade that changes a photoreceptor’s electrical state. It is the central conversion process linking photon capture to a neural signal.
Rod cell: A retinal photoreceptor specialized for sensitive vision in dim light. Rods exemplify high-sensitivity photoreception and do not support color discrimination.
Color vision: The visual capacity to distinguish objects by differences in the wavelengths of their light. Comparisons among cone photoreceptor responses provide the basis for human color vision.
Invertebrate photoreceptor: A light-sensitive cell in an invertebrate visual system, often using a signaling cascade distinct from vertebrate rods and cones. Many invertebrate photoreceptors depolarize in response to light, unlike vertebrate rods and cones.
Rhodopsin: A light-sensitive visual pigment composed of the protein opsin and the chromophore retinal. In rod cells, this pigment initiates the cascade after absorbing a photon.
Cone cell: A retinal photoreceptor that supports color vision and high spatial acuity in brighter light. Cones provide several spectral sensitivities and mediate detailed daylight vision.
Scotopic vision: Vision under dim-light conditions, mediated primarily by rod photoreceptors. Rod sensitivity allows vision when cone responses are too weak.
Melanopsin retinal ganglion cell: A retinal ganglion cell that contains melanopsin and responds directly to light. It detects light without being a rod or cone, especially for non-image-forming responses.
Retinal: A vitamin A-derived molecule that changes shape when it absorbs light. Its light-driven isomerization starts visual signaling in many animal photoreceptors.
Photopigment: A light-absorbing complex formed by an opsin protein and a light-sensitive chromophore. Photoreceptors detect photons through photopigments embedded in their membranes.

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