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The visual system is the physiological basis of visual perception (the ability to detect and process light).The system detects, transduces and interprets information concerning light within the visible range to construct an image and build a mental model of the surrounding environment.
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.
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.
Areas 1 and 2 receive most of their input from area 3. There are also pathways for proprioception (via the cerebellum), and motor control (via Brodmann area 4). See also: S2 Secondary somatosensory cortex. The human eye is the first element of a sensory system: in this case, vision, for the visual system.
The human eye is a sensory organ in the visual system that reacts to visible light allowing eyesight. Other functions include maintaining the circadian rhythm, and keeping balance. Arizona Eye Model. "A" is accommodation in diopters. The eye can be considered as a living optical device.
The structure of a cone cell. Cone cells are shorter but wider than rod cells. They are typically 40–50 μm long, and their diameter varies from 0.5–4.0 μm. They are narrowest at the fovea, where they are the most tightly packed. The S cone spacing is slightly larger than the others. [10]
The basic light-processing unit of eyes is the photoreceptor cell, a specialized cell containing two types of molecules bound to each other and located in a membrane: the opsin, a light-sensitive protein; and a chromophore, the pigment that absorbs light. Groups of such cells are termed "eyespots", and have evolved independently somewhere ...
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. However, these numbers vary greatly among individuals and as a function ...