Term
| Other then color, what is the main aspect of a picture that the visual system gathers info from? |
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Definition
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Term
| What anatomical structure of the eye does light that is the point of focus hit? |
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Definition
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Term
| What type of vision are cones specialized for? |
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Definition
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Term
| What type of vision are rods specialized for? |
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Definition
| Night vision (low light), no color |
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Term
| What two aspects of cells by the fovea permit maximal light transmission to photoreceptor cells? |
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Definition
1. Deviation of bipolar and retinal ganglion cells away from the fovea so light does not need to pass through them
2. Retinal ganglion cells by the fovea are unmyelinated to increase transmission |
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Term
| What contributes to the blind spot in each eye? |
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Definition
| No photoreceptors on the optic disk of each eye |
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Term
| Describe how rods are specialized for low light scenarios and what are some drawbacks of this setup? |
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Definition
1. More photosensitive pigment (more rhodopsin)and high amplification of signal
2. Low temporal resolution and no color vision are the drawbacks |
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Term
| What are the 2 components of rhodospin and what is the function of each? |
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Definition
1. 11-cis retinal - light absorbing molecule
2. Opsin - bound to rhodospin, gives wavelength sensitivity (specific colors for specific cones) |
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Term
| Explain how photons trigger a signal cascade in rhodospin |
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Definition
1. 11-cis retinal is excited by a photon
2. 11-cis retinal is converted to All-trans retinal (causes a conformational change in rhodospin)
3. Activated rhodospin initiates signal cascade
4. Opsin and all-trans retinal are transported to be converted back to original state |
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Term
| What is another name for 11-cis retinal and how is it manufactured? |
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Definition
Vitamen A
It is not manufactored. It is derived purely from diet. |
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Term
| How does activated Rhodospin cause NT transmission in rods? |
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Definition
1. Active rhodospin causes activation of an enzyme that degrades cGMP
2. This causes closing of cGMP gated sodium channels (potassium channels are not cGMP gated and stay open
3. Leads to hyperpolarization of the cell
4. Leads to the release of less glutamate (excitory NT), leads to less spiking |
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Term
| Describe how adaptation to brighter/darker light scenarios occur? |
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Definition
| Sodium channels are also calcium channels. When in the receptor cell, calcium inhibits cCMP synthesis as well as its ability to close the Na channel, altering the sensitivity of the receptor to light |
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Term
| What cell mediates communication between cone cells and what aspect of vision is this critical in? |
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Definition
Horizontal cells
Outer and Inner receptive fields for line detection |
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Term
| Describe how center and surrounding receptive fields function and what are they useful in detecting |
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Definition
1. Cones are linked to their surroundings by horizontal cells
2. Light hitting a cell causes less glutamate to be released
3. This causes depolarization of the on center bipolar cell and hyperpolarization of the off center bipolar cell, which leads to on center ganglion cell depolarization
4. Via the horizontal cell, less glutamate leads to this cell releasing less inhibitory transmitter, causing increased glutamate in adjacent cells, leading to more off firing and less on firing
allows sensing of edges |
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Term
| What is the name for the part of our visual field that can only be seen by one eye? |
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Definition
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Term
| Explain how pupils are dilating and constricting together |
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Definition
| Unilateral input from each eye fed to the pretectum is fed into the Edinger-Westphal nucleus. This nucleus projects bilaterally, however, so both eyes are always in sync |
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