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45 Cards in this Set

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