CLASS 10-17 - CLASS 10 VISION AND HEARING Seeing isnt...

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CLASS 10 – VISION AND HEARING - Seeing isn’t believing Vision: the stimulus - Light is electromagnetic radiation that travels as a wave…the wave travels quickly…the speed of light. - Light waves vary in height or amplitude (which affects brightness) and in wavelength (which affects color) or distance between peaks. - Light can also vary in its purity, which has to do with how many different wavelengths are mixed together - Purity influences the perception of saturation, or richness of colors The eye: converting light into neural impulses - The eye has two main purposes: providing a “house” for the neural tissue that receives light, the retina, and the channeling light toward the retina - The eye is composed of the cornea, a transparent window where light enters the eye, the lens, which is a crystalline structure that lies right behind the cornea and focuses the light rays on the retina. The iris is the colored ring of muscle around the pupil, which constricts or dilates depending on the amount of light present in the environment, and changes the size of the pupil. The size of the pupil regulates the amount of light by constricting to let in less light and vice versa. - Eye has 125 million light detectors - Rods are most sensitive to dim light - Cones: colour and daylight vision The retina - The retina is a piece of neural tissue that lines the back of the eye…it absorbs light, processes images and sends info to the brain - Axons from the retina to the brain converge at the optic disk, a hole in the retina where the optic nerve leaves the eye. If an image falls on this hole, it can’t be seen….the blind spot.
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- The visual receptors cells in the axons are rods (for black and white and low light vision) and the cones (for color and daylight vision) - Adaptation, or becoming more or less sensitive to light as needed, occurs in part due to chemical changes in the rods and cones - Receptive fields are the collection of rod and cone receptors that funnel signals to a particular visual cell in the retina - Lateral antagonism, or lateral inhibition, occurs when the neural activity in a cell opposes activity in surrounding cells The retina and the brain: visual information processing - Light striking the rods and cones triggers neural signals to moves to bipolar cells then to ganglion cells, then along the optic nerve to the optic chiasm, where the optic nerves from the inside half of each eye cross over and project to the opposite half brain. This crossing ensures that signals from both eyes go to both hemispheres of the brain. After crossing, 2 visual pathways exist. The main pathway goes though the lateral geniculate nucleus in the thalamus and on to the primary visual cortex in the occipital lobe. The other goes through the superior colliculus to the thalamus and on to the primary visual cortex. The main pathway is subdivided into two subspecialty pathways, the magnocellular channel and the parvocellular channel. These channels engage in parallel
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This note was uploaded on 04/13/2010 for the course CA 1001 taught by Professor James during the Spring '06 term at Buffalo State.

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CLASS 10-17 - CLASS 10 VISION AND HEARING Seeing isnt...

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