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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.
An opsin absorbs a photon (a particle of light) and transmits a signal to the cell through a signal transduction pathway, resulting in hyper-polarization of the photoreceptor. Rods and cones differ in function. Rods are found primarily in the periphery of the retina and are used to see at low levels of light. Each human eye contains 120 million ...
After passing through the cornea, light passes through the pupil and then the lens of the eye, where it is bent to a greater degree and focused upon the retina. The retina is where a group of light-sensing cells called photoreceptors are located. There are two types of photoreceptors: rods and cones. Rods are sensitive to dim light, and cones ...
In neuroanatomy, the optic tract (from Latin tractus opticus) is a part of the visual system in the brain.It is a continuation of the optic nerve that relays information from the optic chiasm to the ipsilateral lateral geniculate nucleus (LGN), pretectal nuclei, and superior colliculus.
The visual pathway consists of structures that carry visual information from the retina to the brain.Lesions in that pathway cause a variety of visual field defects. In the visual system of human eye, the visual information processed by retinal photoreceptor cells travel in the following way:
The visual cycle is a process in the retina that replenishes the molecule retinal for its use in vision.Retinal is the chromophore of most visual opsins, meaning it captures the photons to begin the phototransduction cascade.
Schematic diagram of pupillary light reflex neural pathway. Left direct light reflex involves neural segments 1, 5, and 7. Segment 1 is the afferent limb, which includes the retina and optic nerve. Segments 5 and 7 form the efferent limb. Left consensual light reflex involves neural segments 2, 4, and 7. Segment 2 is the afferent limb.
The optical path difference between the paths taken by two identical waves can then be used to find the phase change. Finally, using the phase change, the interference between the two waves can be calculated. Fermat's principle states that the path light takes between two points is the path that has the minimum optical path length.