CH 5 Summary Flashcards
You see because light strikes your retina
causing it to send a message to your brain. You send no sight rays out to the object.
According to the law of specific nerve energies
the brain interprets any activity of a given sensory neuron as representing a particular type of sensory information.
Sensory information is coded so that the brain can process it.
The coded information bears no physical similarity to the stimuli it describes.
Light passes through the pupil of a vertebrate eye and
stimulates the receptors lining the retina at the back of the eye.
The axons from the retina loop around to form the optic nerve
which exits from the eye at a point called the blind spot.
Visual acuity is greatest in the fovea, the central area of the retina.
Because so many receptors in the periphery converge their messages to their bipolar cells, our peripheral vision is highly sensitive to faint light but poorly sensitive to detail.
The retina has two kinds of receptors: rods and cones. Rods, more numerous in the periphery of the retina, are more sensitive to faint light.
Cones, more numerous in the fovea, are more useful in bright light.
People vary in their number of axons from the retina to the brain.
Those with more axons show a greater ability to detect brief, faint, or rapidly changing stimuli.
According to the trichromatic (or Young-Helmholtz) theory of color vision
color perception begins with a given wavelength of light stimulating a distinctive ratio of responses by the three types of cones.
According to the opponent-process theory of color vision, visual system neurons beyond the receptors respond with
an increase in activity to indicate one color of light and a decrease to indicate the opposite color. The three pairs of opposites are red-green, yellow-blue, and white-black.
According to the retinex theory, the cortex compares the
responses across the retina to determine brightness and color of each object.
For genetic reasons, certain people are unable to distinguish one color from another.
Red-green color deficiency is the most common type.
