Physiology Flashcards
Types of photoreceptors
rods and cones
how many types of cones are there
3
function of photoreceptors
convert electromagnetic radiation into electrical signals
photoreceptors have an already hyper/depolarised resting membrane potential
depolarised
light exposure causes hyper/depolarisation in photoreceptors
and how?
HYPERpolarisation
light closes the cGMP Na+ channel by reducing cGMP concentration meaning less is available to bind to the Na channel causing it to shut
hyperpolarisation from light exposure causes an increase/decrease in glutamate release
decrease
Dark current is produced from open/closed cGMP Na+ channel
open
what happens when the cGMP Na+ channel is closed
there is less Na influx resulting in hyperpolarisation
in the dark, Na channels are open/closed leading to more/less glutamate production
open
more
in response to light, Na channels are open/closed leading to more/less glutamate production
closed
less
what is visual acuity determined by
photoreceptor spacing and refractive power
rods let you see in normal/dim light
dim
rods have high convergence, what does this mean
more rod cells to 1 ganglion
what effect does a high convergence have on light sensitivity and acuity
higher convergence –> greater sensitivity, lower acuity
cones let you see in dim/normal light
normal daylight
cones have a high/low convergence
what does this mean
low
fewer cone cells to 1 ganglion
better acuity, less sensitivity
what is the fovea
found on centre of macula in the retina that has the greatest concentration of cones
Rods are: a/chromatic peripheral/central retina high/low convergence high/low light sensitivity high/low visual acuity
achromatic peripheral retina high convergence high light sensitivity low visual acuity
Cones are: a/chromatic peripheral/central retina high/low convergence high/low light sensitivity high/low visual acuity
chromatic central retina low convergence low light sensitivity high visual acuity
the right visual field is processed by the left/right side of the brain
left
superior visual field is processed by the upper/lower cortex
lower
