Unit 6: Sensation (cont.)
|
VISION (cont.) Light waves stimulate rods & cones which synapse to bipolar cells, which synapse to ganglion cells. The axons of the ganglion cells come together to form the Optic nerves which transmit visual information to the brain. Blindspot: The area in the retina where the optic nerve leaves the back of eye. No rods or cones are located there, so no vision is possible at that location. Feature Detectors: Nerve cells in the brain that respond to specific features of a visual stimulus, such as shape, angle, or movement. Parallel Processing: The ability of the brain to process several aspect of a situation simultaneously. COLOR VISION Young-Helmholtz Trichromatic Theory: The theory that the retina contains three different types of cones--one most sensitive to red, one to blue, and one to green--which when stimulated in combination can produce any color. RED, GREEN, & BLUE are the PRIMARY COLORS OF LIGHT WAVES. Opponent Process Theory: Theory that opposing retinal processes (red-green, yellow-blue, & black-white) enable color vision. For example some cells are stimulated by red while inhibited by green; others are stimulated by yellow, while inhibited by blue. This helps explain afterimages. Color constancy: Perceiving familiar objects as having consistent color, even if changing illumination alters the wavelength reflected by the object. AUDITION Audition: The sense of hearing. Frequency: The number of complete wavelengths in a given period of time. Frequency determines pitch. Amplitude: Height of each wavelength--determines loudness. Sound Localization: Sound waves strike one ear sooner and with more intensity than the other ear. With this information, the brain can determine the location of the sound. |
 Middle Ear: Chamber between the eardrum and the oval window which contains the ossicles (three tiny bones--hammer, anvil, & stirrup) which concentrate the vibrations of the eardrum. Inner Ear: Contains the cochlea, semicircular canals, and vestibular sacs. Cochlea: a coiled, bony, fluid-filled tube through which sound waves trigger nerve impulses. Basilar Membrane: Membrane along the center of the cochlea that contains hair cells (the receptor cells for sound). Axons from the hair cells for the Auditory Nerves, which transmit neural impulses to the brain. PITCH PERCEPTION Place Theory: Theory that the pitch we hear is associated with the place where the basilar membrane is stimulated. Best for explaining high-pitched tones. Frequency Theory: Theory that the rate of nerve impulses traveling up the auditory nerve matches the frequency of the tone we are hearing. Best for explaining low-pitched tones. Volley Principle: Helps explain in frequency theory how we can hear sounds with a frequency greater than 1000 cycles per second. While some neurons are "recharging" during the refractory period, others are firing. Conduction Deafness: Caused by damage to the structures that conduct sound waves through the ear (eardrum, ossicles). Nerve Deafness: Caused by damage to the cochlea's hair cells or the auditory nerve. NEXT PAGE |