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Visual Agnosia
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-Inability to recognize identity or nature of sensory stimuli
-Certain structures are for recognizing faces while others are for recognizing objects (no same structure does both) -Sensory processing is unaffected |
Apperceptive Agnosia
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Inability to recognize objects
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Prospagnosia
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Inability to recognize faces
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Stimulus for vision
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-Electromagnetic radiation - light reflecting off objects
-Energy travels in waves |
Wavelength
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-Allows us to perceive color
-Short wavelength = high frequency -Long wavelength = low frequency -Different wavelengths result in different colors |
Amplitude
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-Allows us to perceive brigthness
-Amplitude is the height of the wavelength |
Electromagnetic Spectrum
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-A continuum of electromagnetic energy that that is produced by electric charges and radiated as waves
-Very wide spectrum and humans can only see a small portion, this is referred to as visible light -Human range = 400-700 nanometers |
Cornea
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-Transparent membrane covering the outer eye
-Helps protect the pupil and the eye from outside irritants -Allows light to pass through it so it can go to the other structures -More pain receptors than anywhere else on the body |
Pupil
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-Hole in the center of the eye
-Regulates the amount of light coming into the eye by the expanding and contracting iris muscles that surround it -Dark = large pupil, Light = small pupil |
Lens
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-Focusing element of the eye which light passes after passing through the cornea
-Changes size depending on the distance of an object = this is reffered to as "accomodation" -Changes concavity - the lens must be thin to perceive far objects and more round to perceive closer objects |
Iris
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-Thin, circular structure that is responsible for controling the diameter and size of the pupil and thus the amount of lgiht entering the retina
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Retina
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-A complex network of neurons that covers the inside back of the eye
-These cells include the photoreceptors, horizontal cells, bipolar cells, and ganglion cells -Where sensory transduction occurs -Flow of impulses in the retina: Photoreceptors (rods and cones) are stimulated by incoming light --> sends signal to the retina --> the bipolar cells accept signals from rods, cones, or horizontal cells and pass it to the ganglion cell --> impulse goes back through the eye from the photoreceptors to the ganglion cells --> ganglion cell axons are attached to the optic nerve and the impulse is then sent to the LGN via the optic nerve |
Fovea
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-A small area in the retina that contains only cone receptors
-Located on the line of sight so when you are looking directly at an image, it is falling on the fovea -Results in details and sharp vision |
Optic Nerve
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-Bundles of nerve fibers that receive input from the ganglion cells and sends to the LGN
-Each optic nerve contains about 1 million ganglion cell fibers |
Blind Spot
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-Area near the optic nerve where the are no cone or rod receptors
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