The basic structure of the retina has been indicated earlier. As in other parts of the nervous system, the messages initiated in one element are transmitted, or relayed, to others. The regions of transmission from one cell to another are areas of intimate contact known as synapses. An impulse conveyed from one cell to another travels from the first cell body along a projection called an axon, to a synapse, where the impulse is received by a projection, called a dendrite, of the second cell. The impulse is then conveyed to the second cell body, to be transmitted further, along the second cell’s axon.
It will be recalled that the functioning cells of the retina are the receptor cells—the rods and cones; the ganglion cells, the axons of which form the optic nerve; and cells that act in a variety of ways as intermediaries between the receptors and the ganglion cells. These intermediaries are named bipolar cells, horizontal cells, and amacrine cells.
A-horizontal-cross-section-of-the-human-eye-showing-theA horizontal cross section of the human eye, showing the major parts of the eye, including the …[Credits : Encyclopædia Britannica, Inc.]
Horizontal-section-of-the-eyeFigure 1: Horizontal section of the eye.[Credits : Encyclopædia Britannica, Inc.]
Structure-of-the-retinaStructure of the retina
Muscles-of-the-right-eyeMuscles of the right eye
Myopia-or-nearsightedness-can-be-corrected-with-glasses-that-haveMyopia, or nearsightedness, can be corrected with glasses that have concave lenses to allow near …[Credits : Encyclopædia Britannica, Inc.]
Hyperopia-or-farsightedness-can-be-corrected-with-glasses-that-containHyperopia, or farsightedness, can be corrected with glasses that contain convex lenses to reduce …[Credits : Encyclopædia Britannica, Inc.]
Visual-pathwaysVisual pathways
Perimeter-chart-showing-normal-visual-field-figures-on-the-perimeterFigure 2: Perimeter chart showing normal visual field; figures on the perimeter indicate degrees of …[Credits : Encyclopædia Britannica, Inc.]
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