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14 Cards in this Set
- Front
- Back
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What is the purpose of the photoreceptor?
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- transduce energy to neural message
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What is Rhodopsin? and its parts?
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- photo pigment in rods (which only have 1 type of pigment)
-2 parts~ membrane bound protein and Retinal (Vit A) |
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What is the 'path of rhodopsin'?
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- completed through secondary messangers
1. rhodopsin is activated 2. changes shape of the G protein transducin 3. activated transducin changes shape of phosphodiesterase (PDE) 4. Activated PDE changes cyclic GMP to GMP 5. GMP hyperpolarizes GMP 6. output is decreased |
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Describe cones
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- 3+ pigments
- opsin selective (red, green, and blue sensitive) |
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Describe the 3 parts of rods/cones
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1. outer segment (discs with photopigment)
2. inner segment (cell body) 3. synaptic endings (where light hits) |
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What are the major and minor conributors to the high intensity range of the photoreceptors?
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Minor~ pupil sizze
Major~ rods/cones have various areas of specialization AND retinal processing |
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Describe the 2 components of retinal processing
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1. spectral contrast
2 spatial contrast |
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What is spectral constrast?
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- changes in color
- Requires the comparison of at least 2 cones (1 cone tells nothing) |
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What is spatial contrast?
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- Center-Surround antagonism
- compares changes in brightness via input from different retinal locations |
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Describe the Radial Path
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- Sign conserving of the center photoreceptor
- The photoreceptor (when light hits) depolarizes so the bipolar cell depolarizes so the ganglion cell depolarizes and the optic nerve has a decrease in AP |
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Describe the lateral path
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- Horizontal cells have a sign inverting component
- whatever signal the surround photoreceptors transduce, the horizontal cells invert this sign to the bipolar cell |
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What determines if glutamate is excitatory/inhibitory?
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- the post synaptic cell
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In the sign conserving scenario the OFF response is due to? the ON response is due to?
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OFF~ centered white spot
ON~ centered dark spot |
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Lateral inhibition that causes depolarization of the ganglion cell occurs when?
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- when there is a white spot in the surround
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