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70 Cards in this Set
- Front
- Back
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What ions in the RPE aid in movement of water.
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Cl- and K+
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The eye is like a battery where the cornea is ______ and retina/rpe is ________.
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cornea is positive
retina/rpe is negative |
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what is lipofuscin?
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undigested material that what pahgocytosed by RPE
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VEGF secreted by the RPE is important for maintenance of?
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choriocapillaris
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true or false
The RPE helps to reduce scatter of light |
True
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Chromophore (11-cis-retinal) is derived from?
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vitamin A
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What is the difference between ganglion cells and photoreceptors of the retina?
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ganglion cells- triggered by AP, cell depolarizes to send signal
photoreceptors-graded potential, cell hyperpolarizes to send signal |
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When light enters the system, cGMP channels _____ and glutamate _____.
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cGMP channels close
glutamate shuts off (decreases) |
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Ionotropic receptors are on ON or OFF bipolar cells.
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Off bipolar cells
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On bipolar cells have what kind of receptors.
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Metabotropic
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metabotropic receptors on ON bipolar cells are indirectly linked to?
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ion channels
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what type of channels are used by ionotropic receptors?
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ligand gated ion channels
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On center bipolar cells are flat/invaginating.
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invaginating
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What type of cells are parvo and mango cells?
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ganglion cells
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What neurotransmitters are released by amacrine cells?
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GABA, GLYCINE
dopamine in some |
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what is the importance of muller cells?
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help to support and balance fluids
regulate ions -regulate water by moving potassium ions |
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How long does dark adaptation take from sunlight to complete darkness?
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20-30 min
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how long does light adaptation take, from complete darkness to bright light?
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5-10min
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What ion controls light and dark adaptation?
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Ca2+
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What are some factors that affect dark adaptation?
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-intensity and duration of pre-adaption light
-wavelength distribution of the light used -rhodopsin regeneration -size and position of the retinal used in measuring dark adaptation |
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What types of things alter dopamine?
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every drug that affect pleasure, cocaine, amphetamine, opiates marajuana
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GABA neurotransmitter can be altered by what type of drugs?
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depressant drugs, marijuana
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photoreceptors have an increased/decreased oxygen demand than other CNS neurons.
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increased
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True or false
Muller cells store glycogen, and is the main source of glucose for the retina. |
False
-muller cells store glycogen, but hold it in reserve just in case -the main source of glucose to the retina is from the choroid |
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The a-wave represents photoreceptors/bipolar cells?
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photoreceptors
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In an electroretinogram the b-wave represents?
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bipolar cells, glial cells
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Why is too much VEGF a problem?
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get neovascularization
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What type of junctions are found in the RPE? specifically.
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zona occludens
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What is the resting potential of the eye?
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6mV
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In scotopic light, do we have color vision? Are both rods and cones working?
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No color vision
rods only |
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what is phototransduction?
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photon of light is changed into an electrical signal
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The basic job of a chromophore is?
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absorb light
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Basic job of opsin?
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determine wavelength of light
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In rods, opsin is called?
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rhodopsin
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In the dark photoreceptors are______.
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DEPOLARIZED
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True or false
In the dark, photoreceptors are actively secreting neurotransmitter. |
True
-glutamate |
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In the dark, what kinds of voltage gated channels are open?
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Ca2+
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What is the cause of the dark current?
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movement of Na+ from inner to outer segment of the photoreceptor.
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During the dark current, On the inner segment, how does Na+ get out of the photoreceptor?
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Na-K-Pump
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How is Na+ able to enter the outer segment of the photoreceptor during the dark current?
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ligand gated Na+ channels
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What is the membrane potential during the dark current?
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-40mV
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What does the dark current do to photoreceptors?
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keeps photoreceptors depolarized
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What occurs when light enters the system?
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cGMP channels close, Na+ flow shuts off, PR hyperpolarizes, Ca2+ channels close, decrease in Glu release, depolarization of ON center bipolar cells
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When light comes into the system, 11-cis retinol, is converted to?
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all-trans-retinol
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What does all-trans retinol activate?
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transducin
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How does transducin become activated?
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activated by all-trans-retinol, and GDP is exchanged for GTP.
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Once a-GTP unit dissociates from transducin, what does this subunit activate?
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phosphodiesterase
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How does phosphodiesterase play a role in light perception?
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causes breakdown of cGMP to 5'GMP
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What type of channel is Ca2+?
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Voltage gated
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What is the minimum number of photons needed to set off the phototransduction pathway?
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5-14 photons
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All photoreceptors are ______ cells.
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OFF
-they depolarize in the dark |
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All rod bipolar cells are ____ bipolar cells.
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ON
-depolarize when the light is on |
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In the fovea all cones connect to ___ and ____ midget bipolar cells.
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ON and OFF
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Where do bipolar cells send information to?
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ganglion cells
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How do ganglion cells send information?
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AP!
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Receptive fields of ganglion cells respond to _____ and _____.
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gratings and color
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There are "red/_____" ganglion cells.
There are "blue/______" ganglion cells. |
red/green
blue/yellow |
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Horizontal cells are depolarized in the _____. Therefore ligand gated channels _____ in the light.
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Dark
close in the light |
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Horizontal cells send inhibitory/activating messages to the cones.
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inhibitory
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True/false
All amacrine cells have receptive field properties. |
false
Some have receptive field properties |
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Muller cells help to recycle ____.
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all-trans retinal
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Which takes a longer time to desensitize to red or blue.
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blue takes longer to desensitize to.
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Recovery from light requires regeneration of _____. and rapid restoration of _____ concentration.
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rhodopsin
cGMP |
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Depolarization of bipolar cells increases what extracellular ion.
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K+
in OPL |
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Depolarization of bipolar cells and muller cells cause what wave to be seen in an ERG? Is this wave positive or negative.
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B-wave
positive wave |
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hyper polarization of photoreceptors cause what wave to be seen in an ERG? Is this wave positive or negative?
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A-wave
negative wave |
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Basic purpose of the ERG?
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measure retinal function
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In congenital S. night blindness, where is the problem, using an ERG?
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scotopic lighting, no B-wave, therefore defective rod bipolar cells
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Is CSNB hereditary?
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yes
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True/false
Visual field testing can tell us where a problem would be in the visual pathway. |
False
- only tell how well the entire pathway functions |
