2.2 post-receptoral neurons

what are the three types of horiozontal cells in the post-receptoral neurons

H1, H2, H3

function of H1 horizontal cell

receive input mainly from both L- and M-cones

function of H2 horizontal cell

receive input mainly from S-cones but also from L- and M-cones

function of H3 horizontal cell

receive input from all three cone types

how do H cells transmit signal

laterally and not vertically

how do horizontal cells communicate with photoreceptors?

after receiving input from photoreceptors stimulated by light, horizontal cells transmit input to neighbouring photoreceptors (telling neighbours only

do H cells have big or small receptive fields

big

how many different bipolar cells are there in the primate retina

9-10

which cone bipolar cell connect to a single cone in the fovea, preserving maximum spatial resolution (acuity)

midget bipolar cells

which cone bipolar cell connect to multiple cones?

diffuse bipolar cells

rod bipolar cells has no center-surround and only has what type of cells

only ON cells

what cones are we find in the center of midget bipolar cells?

L or M cones

what cones are we find in the surround of midget bipolar cells?

L or M cone

if we find L cone in the center of midget bipolar cell, what cone do we find in the surround

M cone

if we find M cone in the center of midget bipolar cell, what cone do we find in the surround

L cone

what cones are we find in the center of diffuse bipolar cells?

L and M cones

what cones are we find in the surround of diffuse bipolar cells?

L and M cones

what cones are we find in the center of S-cone bipolar cells?

S cones

what cones are we find in the surround of S-cone bipolar cells?

L and M cones

how does the size of midget bipolar cells change in the retina

smaller in central retina (fovea) and larger in peripheral retina

what are the three different rod-to-bipolar interactions?

rod-to-rod bipolar cell, rod-to-cone bipolar cell through gap junctions with cones, rod-to-cone ON and OFF bipolar cell

which photoreceptor cell have a higher degree of convergence?

rods

at the parafovea, how many cones are connected to a single bipolar cell

few, around 1-7

at the parafovea, how many rods are connected to a single rod-bipolar cell

15-30

how many types of amacrine cells are there

22

function of amacrine cells

transmit signals both vertically (bipolar to ganglion cells) and laterally (bipolar to bipolar cells)

how many types of ganglion cells are identified

17

three types of ganglion cells

midget, parasol, small bistratified

which bipolar cells correspond to the midget ganglion cells?

midget bipolar cell

which bipolar cells correspond to the parasol ganglion cells?

diffuse bipolar cell

which bipolar cells correspond to the small bistratified ganglion cells?

S-cone bipolar cell

what is the special photopigment synthesized by and stays inside Intrinsically Photosensitive Retinal Ganglion Cells (ipRGCs)?

melanopsin

what wavelengths are melanopsin sensitive to

short

what is the peak sensitivity of melanopsin

488 nm

what is the function of melanopsin photopigments inside the ipRGC membrane

directly absorb light to depolarize the ipRGC independently.

what structure is responsible for regulation of circadian rhythms and pupillary light reflex instead of forming visual images

melanopsin

main functions of melanopsin

Regulation of Circadian Rhythms and Pupillary Light Reflex

what are the complications due to absence of melanopsin

sleep disorders and seasonal affective disorder

how does the absence of melanopsin lead to sleeping disorders?

Defective melanopsin signaling fails to suppress daytime melatonin

how does the absence of melanopsin affect circadian rhythms

light-signaling pathway breaks down and disrupt circadian rhythms, causing our internal clock to be in a free running state

how does the blue light in our phone affect our sleeping schedule at night?

exposure to blue light from smartphones and screens artificially activates melanopsin, tricking the brain into thinking it is daylight and delaying sleep onset.

why do some cataract patients improve sleep after surgery?

because the opaque lens that absorbs blue light is surgically removed

How does the neurotransmitter glutamate differently affect On-center and Off-center bipolar cells?

Glutamate is inhibitory for On-center cells and excitatory for Off-center cells.

Which retinal cells are the first in the visual pathway to generate true action potentials rather than graded potentials?

amacrine cells

In the presence of light, the concentration of cyclic GMP (cGMP) in a rod outer segment:

decreases, causing sodium channels to close and the cell to hyperpolarize

Which ganglion cell type is characterized by a 'sustained' response to light and provides high spatial resolution?

midget ganglion cells

Which finding led researchers to realize that IPRGCs existed, even before they were morphologically identified?

Blind mice with no rods or cones still exhibited a pupillary light reflex.

which bipolar cell has single cone input and colour opponent ?

midget bipolar cell

which bipolar cell has multiple cone input and non-colour opponent

diffuse bipolar cell

in bipolar cells, does on-center depolarize or hyperpolarize to light?

depolarize

in bipolar cells, does off-center depolarize or hyperpolarize to light?

hyperpolarize

three main functions of amacrine cells

transient responses, motion coding, action potential generation

in ganglion cells, which cell has a sustained response and is responsible for colour?

midget (parvo)

in ganglion cells, which cell has a transient (short) response and is responsible for motion?

parasol (magno)