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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.
Rod cells are photoreceptor cells in the retina of the eye that can function in lower light better than the other type of visual photoreceptor, cone cells.Rods are usually found concentrated at the outer edges of the retina and are used in peripheral vision.
Visual phototransduction is the sensory transduction process of the visual system by which light is detected by photoreceptor cells (rods and cones) in the vertebrate retina.A photon is absorbed by a retinal chromophore (each bound to an opsin), which initiates a signal cascade through several intermediate cells, then through the retinal ganglion cells (RGCs) comprising the optic nerve.
Overview of the retina photoreceptors. ipRGCs labelled at the top-right. Intrinsically photosensitive retinal ganglion cells (ipRGCs), also called photosensitive retinal ganglion cells (pRGC), or melanopsin-containing retinal ganglion cells (mRGCs), are a type of neuron in the retina of the mammalian eye.
There are about 0.7 to 1.5 million retinal ganglion cells in the human retina. [2] With about 4.6 million cone cells and 92 million rod cells, or 96.6 million photoreceptors per retina, [3] on average each retinal ganglion cell receives inputs from about 100 rods and cones.
The retina (from Latin rete 'net'; pl. retinae or retinas) is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs.The optics of the eye create a focused two-dimensional image of the visual world on the retina, which then processes that image within the retina and sends nerve impulses along the optic nerve to the visual cortex to create visual perception.
A dorsal ocellus consists of a lens element and a layer of photoreceptors . The ocellar lens may be strongly curved or flat. The photoreceptor layer may also be separated from the lens by a clear vitreous humour. The number of photoreceptors also varies widely, but may number in the hundreds or thousands for well-developed ocelli.
Photoreceptor cell, a photosensitive cell in the retina of vertebrate eyes; Simple eye in invertebrates (Ocellus), photoreceptor organ ("simple eye") of invertebrates often composed of a few sensory cells and a single lens; Eyespot apparatus (microbial photoreceptor), the photoreceptor organelle of a unicellular organism that allows for phototaxis