Retina Flashcards
when image is focused on the fovea, person sees the object in colour
- cone cells detect colour
- cone cells concentrated at the fovea
- three types of cone cells absorb different wavelength
fovea has high visual acuity
no retinal convergence
each cone cell connected to separate bipolar neuron
impulses from each receptor kept separate
fovea = low sensitivity to light
other parts of the retina = high sensitivity to light
many rods in other parts of the retina
rhodopsin (rod cell pigment) = sensitive to light
rods connected in groups to one bipolar neurone
generator potentials combine to reach threshold
trigger action potential
image in more detail
if mainly rod cells
they share convergence on one bipolar neurone
how would number and distribution of rods and cones across the retina would differ in a nocturnal mammal from a human
more rod cells present mainly in fovea
with high sensitivity to light
rhodopsin bleached at low light intensities
it takes time for the rod cells to recover their sensitivity to light after moving into darkness
rhodopsin is bleached and needs time for resynthesis
white light in rod cells
white has wavelengths that rhodopsin not sensitive to
man sees star at edge of vision
a) why is it seen at edge
b) why is it not seen when looking straight
a) image falls on rod cells
rhodopsin has high sensitivity to low light
rod cells sensitive to low light due to convergence
b) image falls on fovea
cones present in fovea = low sensitivity to light
faint light does not stimulate cone cells
no image?
no photoreceptors
