Retina Flashcards
the […] is an area of the retina that controls central vision. It’s loss causes blindness and its dysfunction is implicated in macular degeneration.
fovea
in photopic light conditions, the best visual acuity is [….] focused on […] in the fovea.
whereas in scotopic light levels, best VA is [….] at […..].
6/6
cones
6/60
rods and rod pathways
light passes through all the retinal layers prior to hitting the photoreceptors, name them in succession
inner plexiform layer
inner nuclear layer
outer plexiform layer
outer nuclear layer
rods are specialized for [….] vision, or […] conditions.
approx how many are there?
which part of retina are they absent from?
night vision
scotopic conditions
100 million
absent from fovea
cones are specialized for [….] vision, or […] conditions.
how many types?
approx how many are there total?
which part of retina are they densest?
day vision, photopic conditions, AND color vision
3 types
densest in the fovea
describe the 3-part ‘through pathway’ of the retina?
photoreceptors —> ? —-> ?
modification of the through pathway occurs by […..] and […] cells
photoreceptors link to bipolar cells link to ganglion cells
amacrine cells and horizontal cells.
in the through pathway, there are ten types of bipolar cells, 1 is a rod bipolar cell, the other 9 are [….] cells
cone bipolar cells.
horizontal cells receive input from photoreceptors and then function to laterally inhibit photoreceptors via the NT, [….]. They respond to light by […].
GABA.
hyperpolarizing.
amacrine cells are axonless cells that are important for […].
They release the NT’s:
These are responsible for modifying the way bipolar cells signal on to […..] cells.
lateral inhibition.
GABA and glycine.
ganglion
the ganglion cell layer contains ganglion cell bodies and some displaced […..] cells.
the ganglion cells are the main output neurons of the retina, there are several types: [….]
These cells release the NT, [….], and are the only ones within this through pathway that are capable of [….]
amacrine.
on, off, P (color), and M (motion)
glutamate
firing action potentials.
ganglion cells respond to light by increase or decreasing […..]
their action potential firing rate.
the […..] of a ganglion cell or bipolar cell is the area of retina that when stimulated with light changes the cells membrane potential.
receptive field
the concentric-sorround receptive field of the ganglion cell means that
depending on where the light hits the ganglion receptive field a very different message is communicated onwards
photoreceptors contain […] allow them to respond to light.
rods contain the photopigment, [….].
cones contain the photopigments, [….]
All -opsins bind to [….].
photopigments.
rhodopsin
cone-opsins (few types)
Vitamin A (all-trans retinal)
in response to light, photoreceptors become […..] and use […] as their NT.
Since only [….] cells depolarize in the ‘through pathway’, instead photoreceptors respond to light with [……] in membrane potential.
hyperpolarized.
glutamate.
ganglion.
graded changes
in the dark, photoreceptors have […..] molecular that creates a sodium channel —> allowing continuous influx of sodium ions –> causes […]
cGMP
depolarization of the cell.
in light conditions, light causes cGMP within the photoreceptor to break down into […..]. —> flow of Na ions into the cell ceases —> cell becomes [….]
GMP
hyperpolarized.
OFF bipolar cells become […] in response to light, whereas ON bipolar cells become [….] in response to light.
This is because ON bipolar cells have […..] glutamate receptors and OFF bipolar cells have [….] glutamate receptors.
hyperpolarized
depolarized
ionotropic. (protein subunits–>form an ion channel)
metabotropic (second messenger cascade)
what interaction is there between photoreceptors and on/off bipolar cells and on/off ganglion cells.
photoreceptors communicate with both ON and OFF bipolar cells.in
ON bipolar cells only communication with ON ganglion cells.
OFF bipolar cells only communicate with OFF ganglion cells.
in the centre-sorround receptive field organization, the central response is determined by the […] and the sorround response is determined by […].
through pathway horizontal cells (acting as interneurons)
Horizontal cells receive input from many photoreceptors and provide output to [….].
the ‘sorround response’ results from the action of Horizontal cells on the [….] of photoreceptors.
other photoreceptors.
“central” group”
