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25 Cards in this Set
- Front
- Back
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What is the strongest refractive part of the eye?
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The cornea
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What muscles change the shape of the lens?
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Ciliary muscles
Relaxed when flat |
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During accommodation, are the ciliary muscles relaxed or contracted?
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Contracts
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In myopia (near sighted), where do the light rays converge?
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INSIDE/BEFORE the retina
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In hyperopia, where do the light rays converge?
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BEHIND the retina
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Where do the light rays converge in an astigmatism?
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Point behind the retina and dispersed to create a blurred image
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What are the 3 layers of the retina (from outside to inside)?
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1. Ganglion cell layer
2. Inner Nuclear Layer 3. Outer Nuclear Layer |
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What are the only cells in the retina that actually produce AP's?
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ganglion Cells
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What layer contains the photoreceptors?
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Outer Nuclear layer
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Inner Nuclear Layer contains what type of cells?
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Horizontal cells, Bipolar cells, amacrine cells
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What are the 2 characteristics of the fovea that allows to increase visual acuity?
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1. No blood vessels
2. Inner nuclear and ganglion cell layers removed so only photreceptors (outer nuclear layer) is present |
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The fovea only contains what type of photoreceptor?
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Cones
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What are the 3 colors of cones?
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Red, Green, Blue
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What is the protein that captures photons?
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Rhodopsin
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What is the signal cascade when a rod absorbs a photon?
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1. Rhodopsin activate G protein
2. G protiein activates enzyme that degrades cGMP to GMP 3. Removal of cGMP CLOSES cCMP gates Na+ channel and HYPERPOLARIZES cell |
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In the dark, what is the state of photreceptors in terms of release of NT and polarization?
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DEPOLARIZED are CONSTANTLY releasing glutamate
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What cell synapses on photoreceptors?
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2 Bi-polar cells (one off/one on) on each photoreceptor
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What are the 2 types of bi-polar cells?
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1. On-bipolar - glutamate is inhibitory. Become depolarized as light INCREASES
2. Off-bipolar - glutamate i excitatory. Become hyperpolarized in the light |
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What cells compose the 2 major LATERAL pathways in the retina?
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1. Amacrine (inner plexiform layer)
2. Horizontal Cells (outer plexiform layer) |
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What are Horizontal cells in terms of NT and action?
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GABAergic and their action is always OPPOSITE to that of the photoreceptor input
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What is the relationship between photreceptor input and H-cell input?
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ANTAGONISTIC
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Receptive fields have what type of organization?
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Center-surround
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What is the function of the ganglion cells?
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Merely recode the bipolar signal into spikes
Have ON-ganglion cells and OFF-gaglion cells |
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What are the 2 main types of ganglion cells?
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1. Midget - receive from single bi-polar cells. Tiny RF's, good acuity, small dendritic tree.
2. Parasol - Receive from many bi-polar cells. Large RF, poor acuity, SENSE MOTION |
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M cells are what?
P cells are what? |
M cells = parasol
P cells = midget |
