Editing Photoreceptor cell (section)


{{Short description|Type of neuroepithelial cell}}
{{About|cellular photoreceptors|other types of photoreceptors|Photoreceptor (disambiguation)}}
{{Infobox neuron
|name = Photoreceptor cell
|image =1414 Rods and Cones.jpg
|caption = Functional parts of the [[rod cell|rods]] and [[cone cell|cones]], which are two of the three types of photosensitive cells in the retina
|location =
|function =
|neurotransmitter  =
|morphology =
|afferents =
|efferents =
}}

A '''photoreceptor cell''' is a specialized type of [[neuroepithelial cell]]  found in the [[retina]] that is capable of [[visual phototransduction]]. The great biological importance of photoreceptors is that they convert light (visible [[electromagnetic radiation]]) into signals that can stimulate biological processes. To be more specific, [[photoreceptor protein]]s in the cell absorb [[photon]]s, triggering a change in the cell's [[membrane potential]].

There are currently three known types of photoreceptor cells in mammalian eyes: [[rod cell|rods]], [[cone cell|cones]], and [[intrinsically photosensitive retinal ganglion cells]]. The two classic photoreceptor cells are rods and cones, each contributing information used by the [[visual system]] to form an image of the environment, [[Visual perception|sight]]. Rods primarily mediate [[scotopic vision]] (dim conditions) whereas cones primarily mediate [[photopic vision]] (bright conditions), but the processes in each that supports phototransduction is similar.<ref>"eye, human." Encyclopædia Britannica. Encyclopædia Britannica Ultimate Reference Suite. Chicago: Encyclopædia Britannica, 2010.</ref> The intrinsically photosensitive retinal ganglion cells were discovered during the 1990s.<ref name=Foster>{{cite journal|last1= Foster|first1= R.G.|last2= Provencio|first2= I.|last3= Hudson|first3= D.|last4= Fiske|first4= S.|last5= Grip|first5= W.|last6= Menaker|first6= M.|title= Circadian photoreception in the retinally degenerate mouse (rd/rd)|journal= Journal of Comparative Physiology A|volume= 169|issue= 1|year= 1991|doi= 10.1007/BF00198171|pmid=1941717|pages=39–50|s2cid= 1124159}}</ref> These cells are thought not to contribute to sight directly, but have a role in the entrainment of the [[circadian rhythm]] and the [[pupillary reflex]].