There are a minority of axons that go to the hypothalamus and the olivary pretectal nucleus (OPN). Each pretectal area sends bilateral signals to the preganglionic parasympathetic nuclei in the midbrain called Edinger-Westphal nuclei. The optic tracts join the brachium of the superior colliculus, and then signals travel to the pretectal area of the midbrain. Thus, the right optic tract will contain temporal retinal fibers from the right eye, as well as nasal retinal fibers from the left eye. At the optic chiasm, nasal retinal fibers will cross to the contralateral side of the optic tract, and the temporal retinal fibers continue on the ipsilateral side. The optic nerve then forms the optic chiasm, which diverges into a left and right optic tract. These are the first steps of the pupillary light reflex afferent pathway. The optic nerve sends impulses to the brain for further processing and image recognition. These signals are then relayed to the bipolar cells, which interact with ganglion cells, which in turn coalesce to form the optic disc and optic nerve (CN II). Photoreceptor cells in the outer layers of the retina, which are called rods and cones, convert light stimuli into neuronal impulses. Signal transduction pathway is a mechanism that describe the ways cells react and response to stimulation.Light travels through the cornea, anterior chamber, pupil, lens, and the posterior chamber, eventually reaching the retina. This chain of process is class signal transduction pathway. These cells receive light, and pass on signals to other receiver cells. In human eyes, rod and cones react to light stimulation, and a series of chemical reactions happen in cells. The resulting complex is called rhodopsin or "visual purple". The tops of the rods and cones contain a region filled with membrane-bound discs, which contain the molecule cis-retinal bound to a protein called opsin. The retina is lined with many millions of photoreceptor cells that consist of two types: 7 million cones provide color information and sharpness of images, and 120 million rods are extremely sensitive detectors of white light to provide night vision. The brain then determines, which nerve fibers carried the electrical impulse activate by light at certain photoreceptors, and then creates an image. The rods and cones convert the light into electrical impulses which are transmitted to the brain via nerve fibers. The light image is mapped on the surface of the retina by activating a series of light-sensitive cells known as rods and cones or photoreceptors. The nerve cell carries this impulse to the brain, where the visual information is interpreted. This potential difference is passed along to an adjoining nerve cell as an electrical impulse. As light enters the eye, the 11- cis-retinal is isomerized to the all-"trans" form.Īs the protein changes its geometry, it initiates a cascade of biochemical reactions that results in changes in charge so that a large potential difference builds up across the plasma membrane. Retinol can be convert to retinal, and retinal is a chemical necessary for rhodopsin. Vitamin A is critical for vision because it is needed by the retina of eye. The predecessor of vitamin A is present in the variety of plant carotene. Vitamin A, also known as retinol, anti-dry eye vitamins, is a required nutrition for human health. Light energy can convert chemical to other forms. From long wavelength to short wavelength, energy increase. Light, as waves carry energy, contains energy by different wavelength. However, as an energy wave, energy is passed on through light at different wavelength. Light energy goes into eyes stimulate photoreceptor in eyes. Living organisms sense light from the environment by photoreceptors. Light is one of the most important resources for civilization, it provides energy as it pass along by the sun.
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