Distribution of photoreceptors in the retina
fovea
contains only cones� High density of photoreceptors�
Lack of bipolar, ganglion cell layer� No convergence
Peripheral retina
� contains mostly rods� Density of cones decreasing with
increasingdistance from fovea� Convergence between rods
and bipolar cells,bipolar cells and ganglion cells
Optic disc
� Region where retinal ganglion cell axons bundle toform
optic nerve� No photoreceptors: blind spot
fovea
contains only cones� High density of photoreceptors� Lack
of bipolar, ganglion cell layer� No convergence
Peripheral retina
� contains mostly rods� Density of cones decreasing with
increasingdistance from fovea� Convergence between rods
and bipolar cells,bipolar cells and ganglion cells
Optic disc
� Region where retinal ganglion cell axons bundle toform optic
nerve� No photoreceptors: blind spot
Photopigments confer light sensitivity to ..........
photoreceptors
Photoreceptors have membrane stacks called..... in outer segment
disks
� Disks contain photopigment: .........
Proteins withcovalently bound light-absorbing retinal (cofactor)
� Different photopigments: Rods have,,,,,;............... have
either of three different opsinsabsorbing light at different (overlapping)wavelengths
rhodopsin
cones
Light leads to .................. The opsin initiates a signallingcascade
isomerization of retinal(conformational change from cis to
trans), andactivates the opsin.
.................. dissociates fromopsin and is converted back
to cis-retinal beforere-binding opsin
Light-activated trans-retinal