Physiology of Vision Flashcards
light travels through what structures to get to its desired destination in the retina
ganglion cells then
bipolar cells then
photoreceptors
the direction of visual signals travels from what retinal structure to what?
photoreceptors to bipolar cells to ganglion cells
which lateral connecting cells of the eye are the closest to the photoreceptors
horizontal cells
photoreceptor membranes are usually __polarised at rest
depolarised
in the absence of light there is an influx of what? what happens as a result?
influx of Na aka the dark current causing photoreceptors to be depolarised at rest
what 2 substances bind to form rhodopsin
opsin + 11-cis-retinal
light stimulation of rhodopsin leads to activation of…
transducin (a g protein)
the more cGMP, the more ___ ____
Na entry
which photoreceptors are for dim light?
rods
___ are excluded from the fovea and exist more peripherally
rods
the higher the convergence the ___ visual acuity
less (large spacing over a large area, less will make it more focused)
what chemical is at a low level in photoreceptors in light?
glutamate
what cells are affected when glutamate is low? what happens to them?
bipolar cells (become more negative as there is no depolarisation from glutamate)
what receptors respond positively to glutamate?
ionotropic glutamate receptors
what receptors respond negatively to glutamate?
metabotropic glutamate receptors
what happens to bipolar cells when glutamate is low in metabotropic glutamate receptors
become more negative (less glutamate and these receptors respond positively to this so will hyperpolarise)
there is more glutamate in the dark T or F
T
what is the main aim of lateral inhibition?
allows sensory neurons to LOCALISE the stimulus
horizontal cells are located between
photoreceptors and bipolar cells
what cells are in charge of centre-surround organisation (a form of lateral inhibition) in the retina?
horizontal cells
when will an off centre ganglion cell have the highest AP?
when the centre of the visual field is dark and the surrounding area is light
the fovea takes up a small part of the visual cortex T or F
F takes up a very large section (up to half)
first monocular layer of the striate cortex?
layer 4c
first cortical visual area that receives input from the lateral geniculate nucleus?
striate cortex
LGN location?
thalamus
retinal synapses in the LGN are not affected by deprivation, why?
they are monocular not binocular
lesion of the retina causes a…
monocular scotoma
retrochiasmal lesions cause ____ visual fields
homonymous
same visual fields eg nasal and temporal
“macular sparing” makes you think the lesion is in the..
occipital lobe
