Vision Light and Neuronal Activity

humans depend primarily on vision for orientation in the world that surrounds them while image formation is a phenomenon that takes place in the eye the interpretation of the image as a representation of the real world occurs in the brain direct visual signals arriving to the primary cortex called the v1 region which is located in the occipital region of the brain the secondary visual cortex which comprises v2 v3 v4 v5 v6 v7 and v8 regions depends on the v1 region the visual signals are transmitted along the fibers of the optic nerves the fibers mitten cross at the optic kyles the brain does not receive signals from HR unilaterally within one optic nerve the defining group of accents crosses over to join the opposite optic nerve half of each optical field is directed to the observatory portion of the brain the other half is directed to the contralateral portion thus each side of the brain receives visual information from both eyes information from the temporal part of the right visual field passes over to the left hemisphere information from the temporal part of the left visual field passes over to the right hemisphere this is called control it reality of vision let's go back to the beginning once more and observe all di detects the electromagnetic radiation reflected from objects light passes through the cornea pupil and lands on its way to the retina where the visual scene is focused you the lens projects an inverted image onto the retina the same way a camera lens projects an inverted image onto a film the retina is a highly specialized neuronal tissue most of the cells of the retina are neurons among others we have the rods and cones also called photoreceptors the fovea the central region of the retina only has cones these require high levels of light to generate signals does they work best in the tight conditions cones are responsible for color vision and high visual resolution color vision relies on the wavelength specificity of cones which respond to narrow bands of color and also depends on cortical structures which sort the proportional response of the different types of cones in the peripheral regions of the retina rods greatly outnumber cones runs are better contrast sensors and have a major role in peripheral vision they are adapted to them light and cannot work in bright light photo pigments referred to as absence are embedded in stacks of cell membranes in the outer segments of photoreceptors these photo pigments are able to absorb the energy on the visible spectrum with apps in the light-absorbing pigment incorporated in the outer segment discs of the rods contain the prosthetic group called sees retinal the retinal summarizes to an ultra as confirmation upon absorption of light and associates itself from the obscene rhodopsin binds to and activates the two protectors deuce in the activated alpha subunit of just using one stone the cyclic GMP phosphodiesterase phosphodiesterase activation triggers the hydrolysis of cyclic GMP and as a result causing the rapid decline in cytoplasmic cyclic GMP levels in the outer segment of the rod drop in cyclic GMP levels leads to the cation channels closure in the plasma membrane and blockage of sodium and calcium influx consequently the photoreceptor membrane I polarizes generating a direct flow of electric current along the membrane in the dark the polarized rod releases glutamate the neurotransmitter release assaulted when the ipro polarization reaches the synaptic terminal the retinal cells are grouped into main circuits vertical circuit consists of photoreceptors bipolar cells and ganglion cells the modulation circuit consists of horizontal and the macaran cells synaptic terminal of the rod makes contact with bipolar cells the synapses may be modulated by regional cells the reduced glutamate release activates bipolar cells that are I / polarizing the dark and respond to light increments these are called on circuits on the other hand it also inhibited bipolar cells that are the polarized in the dark and respond to light decreases these are called of circuits with suitable inhibitory or excitatory signals information is passed from bipolar to ganglion cells the synapses may be modulated by the immigrant cells and green cells unlike the other retinal neurons do have action potentials it is the changes in light intensity and the shifting of the image over the field of vision that causes a change in the firing rate in ganglion cells the actions of the ganglion cells which are the last neurons in the chain bundle to form the optic nerves that marks the beginning of transmission to the visual processing centers of the central nervous system ACK intermediate way station is a dorsal lateral geniculate nucleus one of the thalamus neuronal nuclei this region of the brain is the site of synapses between the axons of the ganglion cells and a set of cortical thalamic neurons whose projections radiate and carry the signal into the visual cortex activated monocular neurons individual region same output binocular neurons which begin the rendering of images his mechanism is responsible for the stereoscopic vision the image is formed by the two are isn't transmitted to the brains visual cortex are not quite identical this discrepancy compels the brain to compare the two images and to render a single integrated image because the information is interpreted in the visual cortex we may well say that this is where the true vision resides you you

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