The Functions of the Eye, Ear and Skin; Their Role in Behavior
Vision starts with light, the physical energy that stimulates the eye. Light waves coming from some object outside the body are sensed by the eye; the only organ that is capable of responding to the visible spectrum. Eyes convert light to a form that can be used by the neurons that serve as messengers to the brain. The neurons themselves take up a small percentage of the total eye. Most of the eye is a mechanical device that is similar to a traditional, non-digital electronic camera that uses film. Most processing of visual images takes place in the visual cortex of the brain, and it is there that the most complex kinds of processing take place. Many neurons in the cortex are particularly specialized, being activated only by visual stimuli of a particular shape or pattern. This process is known as feature detection. Some cells are activated only by lines of particular width, shape, or orientation; while other cells are activated only by moving. Different parts of the brain process nerve impulses in several individual systems at the same time. Color vision is based on two processes or theories; trichromatic theory and the opponent-process theory. The trichromatic theory states there are 3 kinds of cones in the retina, to which each is responsive to a certain range of colors. The opponent-process theory suggests pairs of different types of cells in the eye that work in opposition of each other. Both theories are at work in allowing a person to see color. The outer ear acts as a reverse megaphone that. It is designed to collect and bring sounds into the internal portions of the ear. Wave patterns in the air enter each ear at a slightly different time, and the brain uses the discrepancy as a clue to the sound’s point of origin. The vibrations of the eardrum are transmitted into the middle ear, which 3 bones are located: the hammer, the anvil, and the stirrup. The job of these bones...
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