![]() Peripheral retina more sensitive to light. The combined effect of these distributions is to make the Ganglion cell is also far greater in the peripheral retina. The number of photoreceptors connected to a single ![]() More numerous, whereas in the centre, at the fovea,Ĭones are. Around the periphery of the retina, rods are far Pattern and physiological characteristics. The endings of these outer segmentsĮvery type of cell in these layers has its own distinctive distribution Outer segments, in which the light-sensitive The outer segment layer, containing the photoreceptors' The nerve endings of bipolar cells, horizontal cells, and photoreceptorĬells, and then the outer nuclear layer, whichĬontains the bodies of the photoreceptor cells. NextĬome the outer plexiform layer, composed of Of the bodies of bipolar, horizontal, and amacrine cells. That comes the inner nuclear layer, composed Plexiform layer, a network of axons and dendritesįrom ganglion cells, bipolar cells, and amacrine cells. The first of these is the ganglion cell layer,Ĭomposed of the bodies of ganglion cells. The photoreceptors, incoming light must first pass throughĪll the other layers of cells in the retina (see sidebar). Thus the analysis of visual stimuli begins even in the retina. Most direct visual pathway, the responses are modified by theĪctivation of lateral connections involving horizontal and amacrineĬells. ![]() Information travels from the photoreceptors to the bipolarĬells and then on to the ganglion cells. The extensions of these cells thus apparently play both roles. These cells in fact have only dendrites, some of which are presynaptic, that is, play the role of axons. Horizontal cells share a special characteristic with amacrine cells: the lack of any extension resembling an axon. The dark pigmentation of this epithelium also prevents unabsorbed photons from being reflected back onto the photoreceptors and thus creating light interference that would degrade the image. Also, after the structural arrangement of the retinene molecules has been changed by the light energy, they are recycled in this epithelium. ![]() Photoreceptors must be in contact with the layer of epithelial cells at the back of the eye, which provide them with a continuous supply of retinene,Ī light-sensitive derivative of Vitamin A. The reason for this somewhat paradoxical arrangement is that the light-sensitive pigments in the Before reaching the photoreceptors, light must travel through all the other layers of the retina. Intuitively, you might expect the photoreceptors to be located in the layer of the retina closest to its inner surface, so that they would receive the incoming light first. ![]()
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