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45 Cards in this Set
- Front
- Back
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what is phototransduction?
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when the pigments in the rod and cone cells absorb light
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what are the photopigments?
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G-protein receptors
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what colors do the rods absorb most strongly in?
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blue-green
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what activates the G-protein receptors in photopigments?
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light
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what exactly is absorbed?
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a single photon of light
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what does the active photopigment molecule stimulate?
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transducin
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what does transducin activate?
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the cGMP phosphodiesterase
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what does cGMP normally do? What happens when cGMP phosphodiesterase acts?
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normally keeps the Na and Ca channels open....this enzyme causes the channels to close.....hyperpolarization
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what is retinis pigmentosa?
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slow degeneration of rods leading to a loss in peripheral vision
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where are the mutations possible in retinis pigmentosa?
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1) rhodopsin
2 )PDE 3) GMP gated ion channel |
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where are mutations possible in congenital stationary night blindness?
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1)rhodopsin
2)PDE 3)transducin |
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what type of rods important for?
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dim light
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what are cones important for?
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day vision
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how many rods do we have compared to cones?
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100 million to 5 million
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what does it mean when the rods are saturated?
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they cannot respond to any more light above that level
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what is the big difference between rods and cones?
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rods saturate and cones do not saturate
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what is your vision usually based on?
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5% of your photoreceptors-> your cones
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what does the retina develop from?
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an outpocketing of the diencephalon
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which neurons have receptive fields?
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all neurons that are in higher order than photoreceptors
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what is a receptive field?
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field of photoreceptors that provide input to a specific higher order neuron...when stimulated, they influence the activity of that neuron.
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what are the inhibitory neurons called that connect photoreceptors?
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Horizontal Cells
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what does excitment of a horizontal cell mean?
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depolarization
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what does an excited (depolarized) horizontal cell do to its neighboring horizontal cells?
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it hyperpolarizes them....(inhibits them)
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what excitatory neurotransmitter do depolarized cones release?
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glutamate
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do photoreceptors produce action potentials?
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no- the more depoarized they are, the more nts they release....the less depolarized the less nts they release...
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what is the inhibitory neurotransmitter released by horizontal cells?
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GABA
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what does GABA do to adjacent horizontal cells?
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hyperpolarizes (inhibits)
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what does light do to all photoreceptors?
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hyperpolarizes....turns them OFF!!!!....release LESS neurotransmitter
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what turns photoreceptors on?
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darkness....they depolarize in the dark!
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what do the surrounding cones exposed to light do to the middle cone that is dark?
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releases the inhibitory action that the surrounding cones have on the central dark cone (turned on)
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what cells release the nuerotransmitter Glutamate?
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the cones
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which cells release the inhibitory neurotransmitter GABA?
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horizontal cells
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photoreceptors can be called "OFF-CENTER" cells or _______ cells?
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"ON-SURROUND"
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what is an "ON CENTER" bipolar cell?
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light in the center of the receptive fields of the bipolar cells turns them ON
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what is the synapse like of an "ON-CENTER" bipolar cell?
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SIGN-REVERSING synapse with cones
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what turns on the ON CENTER bipolar neuron?
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an OFF-CENTER cone (a cone that is turned off or has light going through it)....L side of diagram
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when does glutamate have an inhibitory effect?
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when light shines on the central cone...depolarizes the cone...releases Glutamate... acts on the "ON-CENTER" bipolar cells to hyperpolarize them- turns them OFF!!!!!!!
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what type of synapses do "OFF-CENTER" bipolar cells have?
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special flat synapes...SIGN-CONSERVING synapses
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what type of cells to bipolar cells talk to?
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amacrine cells and ganglion cells
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what do amacrine cells do?
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provide lateral connections and produce transient depolarizing responses
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what type of cells do produce action potentials?
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ganglion cells
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What type of behavior do Parasol ganglion cells exhibit?
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M cell behavior
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What type of behavior do Midget cell ganglion exhbit?
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P cell behavior
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what are the two types of ganglion cells?
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Parasol ganglion cells
Midget ganglion cells |
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what type of ganglion cells are large with large receptive fields?
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Parasol ganglion cells
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