Figure 13-2. Cellular detail of the retina.
a. Visual Fields (Figure 13-3). When a human looks at an object, light from
the right half of the visual field goes to the left half of each eye. Likewise, light from the
left half of the visual field goes to the right half of each eye. Later, in paragraph 13-4,
we will see how the information from both eyes about a given half of the visual field is
brought together by the nervous system.
b. Photoreception and Signal Transmission. The cells of the retina include
special photoreceptor cells in the form of cones and rods. The light ray stimulus
chemically changes the visual chemical of the cones and rods. This produces a
receptor potential which passes through the bodies of the rods and cones and which
acts at the synapses to induce a signal in the bipolar cells. This signal is then
transmitted to the ganglion cells.