Outer Nuclear Layer
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Outer Nuclear Layer
The Outer Nuclear Layer consists of photoreceptors. Photoreceptor cells as the name goes; are in charged of receiving protons or light stimulus in the retina. In fact photoreceptors are not light activated; they are active in the dark. The photoreceptors have pigment molecules (rhodopsin) that when affect by light will break down into 2 molecules (opsin and retinal). The opsin molecule that is released as an enzyme that causes a chemical reaction that will cause the sodium channel to close. Thus the photoreceptors are hyperpolarized by light stimulus and resulting in the closure of the sodium channel. These results in a decrease in the amount of neurotransmitters release or fewer signals sent to the bipolar cell connecting it. With the absence of light when the photoreceptors are active, the chemical reaction of breaking down the rhodospin will be reversed, causing slight opening of the sodium channel. One example will be closing one¡¦s eyes after staring at a bright light. An illusionary bright light will persist because it requires time for the rhodospin to be restored. Photoreceptors are classified into 2 types and they are the cones and the rods. In this project, the data from the rod photoreceptors are simulated using outputs of Web/Video Cam. [1]
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Rods
Rods are used for Black & White vision. They are more in quantity than the cones in the retina. (120 million) They are more contrast sensitive than cones (More than one thousand times as sensitive as the cones) but not sensitive to color. Rods are situated more at the peripheral part of our vision therefore making it more light sensitive thus allowing peripheral vision of dimmer objects. If you see a dim star in your peripheral vision, it may just disappear if you focus your eyes on it. This is because there are less Rods in the Fovea which is the center of the field of view. [1]
Cones
Cones are used for color vision, mainly the center of our vision. There are around 6 to 7 million of cones in our retina. Unlike rods, cones are more concentrated in the center of the retina call the Fovea Centralis. This is a region of 0.3mm diameter rod free area. [1]
Architecture Visual Pathway Outer Nuclear Layer Inner Nuclear Layer Ganglion Cell Layer