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Unformatted text preview: Within the nervous tunic, photoreceptor cells (rods and cones) form synapses with other nerve cells (refer to Figure 1). When stimulated by light, rods and cones pass graded potentials to bipolar cells, which in turn pass graded potentials to the ganglion cells. The graded potentials may be modified by horizontal cells and amacrine cells that link adjacent photoreceptors or ganglion cells, respectively. Action potentials are ultimately generated by ganglion cells. The axons of all the ganglion cells gather at the optic disc and exit the nervous tunic through the optic disc as the optic nerve. The optic disc is a blind spot because photoreceptors are absent here. The lens of the eye consists of tightly packed cells arranged in successive layers (as in an onion) and filled with transparent proteins called crystallins. The lens divides the interior of the eyeball into two cavities: The anterior cavity, the area in front of the lens, is subdivided by the iris and ciliary body into the anterior chamber and the posterior chamber. Capillaries in the ciliary body produce a clear fluid, the aqueous humor, chamber and the posterior chamber....
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This note was uploaded on 11/10/2011 for the course PT 101 taught by Professor Staff during the Spring '10 term at Texas State.
- Spring '10