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31 Cards in this Set
- Front
- Back
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what do photoreceptors do? and how do they do that?
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transduction! transduce light energy into neural signals.
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what are the 2 photoreceptors called and what do they do?
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rods: used for low light, contain rhodopsin as photopigment.
cones: used for color, contain 3 types of opsin for color perception of light. |
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what is the function center of the retina called?
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the fovea.
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what are the anatomical parts of the retina?
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photoreceptors, fovea, foveola & blind spot.
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where is the point of greatest visual acuity in the retina?
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the fovea.
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if you look at the solar eclipse without any protective eyewear, which part of the retina will be severely damaged?
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the fovea.
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what is the bottom of the fovea called? and what type of photoreceptors are found here?
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the foveola is the bottom of the fovea and only cones are found here. there are NO rods!
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what's the blind spot? (not the blindside as in the movie!) which photoreceptors are present?
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it is the point that axons exit the retina and blood vessels enter&leave. there are NO photoreceptors present.
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what is scotopia?
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visual mind loss? look this up. not sure.
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rods vs cones: which has higher sensitivity?
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rods have higher sensitivity.
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rods vs cones: which is specialized for day vision?
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cones are specialized for day vision.
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rods vs cones: which has more photopigment and captures more light?
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rods.
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rods vs cones: which is specialized for night vision?
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rods.
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rods vs cones: which is more sensative to scattered light?
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rods.
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rod vs cone system: which has low acuity & is achromatic?
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rod system.
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what 4 steps happen when the photo receptors are excited? (summarized version)
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1. rhodopsin process
2. light closes Na channels 3. hyperpolarized membrane reduces transmitter release 4. disc membrane response to plasma membrane. |
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during the rhodpsin phase of photoreceptor excitation what's involved?
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a. retinal, all-trans isomers
b. opsin c. come opsin (3 forms) |
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what is significant about retinal?
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it is 11-cis = it's bent. it allows opsin to bind to it.
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what's significant about all-trans isomers?
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they are straight and do NOT let opsin bind to it so opsin floats away.
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opsin will float away in the presence of what? retinal or all-trans isomers?
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all-trans isomers.
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when light closes the Na channels what type of polarization is taking place?
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hyperpolarization.
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when the membrane is hyperpolarized due to the light closing the Na channels, what happens to the transmitter release?
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it is reduced.
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the disc membrane responds to the plasma membrane with what three factors?
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a. cyclic GMP activation
b. phosphodiesterase increases c. passive Na influx, active K efflux (depolarizes membrane) |
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both rods and cone cells have inner and outer segments connected by what?
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a cilium.
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where is the cell's nucleus contained? inner or outer sement?
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inner segment.
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which segment contains the light-transducing apparatus?
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the outer segment.
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cones are most sensitive to direct axial rays because why?
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the shape of the cone's outer segment. it has a stack of membranous discs that contain the light-absorbing photopigments.
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where are the free floating discs located?
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in the outer segment of the rods.
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T/F: the rods have an outer segment that have discs that are open up in the back?
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true.
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do cones release discs? if so/no, what do they do next with them?
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they don't. they recycle&recirculate them! they break them down and then build them back up.
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what is retinitis pigmentosa?
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night blindness = insidious disease. disc form rods are shed off in the back near epithelium. normally disc are taken up and reabsorbed so they can be broken down. but night blind folk can't and the discs build up = toxicity = rods die off = night blindness.
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