Rods, cones, Bipolar and Ganglions

Question 1

Rhodopsin

Answer 1

The protein that changes shape when hit by light. Na+ channels close, membrane hyperpolarizes. This signal gets sent to bipolar and then ganglion cell

Humans have 4 different proteins (1 rod 3 for cones)

Question 2

Trichromatic color vision

Answer 2

Humans have trichromatic color vision’; 3 cone pigments.

Red (actually best to yellow); long wavelength

Green ; Medium wavelength

Blue ; short wavelength

Some birds, fish have 4; tetrachromatic. Eg inc. ultraviolet

Question 3

RGC’s

Answer 3

Retinal ganglion cells, neurons located in the ganglion cell layer of the retina. Help decompress the data and send the signal to the brain. Consist of two types

Question 4

Midget cells

Answer 4

X type RGC’s, have small receptive fields

Typically, center is connected to a single cone. surrounded connected to one other color cone, allowing it to see colour contrast

Thirdly, Midget system has slow sustained responses. Action potentials fire when it’s on

Question 5

Parasol cells

Answer 5

Y type RGC’s. Large receptive fields with loads of dandrites

Center connected to multiple cones, making it not colour selective. This system is colour blind.

Fast and transient response, doesn’t keep firing as it is one, just peaks.

Question 6

Rods

Answer 6

Sensitive enough to respond to a single photon of light, about 100 times more sensitive to single photon than cones. Primary source of visual information at night (scotopic vision)

Sensitive to 1 wavelength, so useless for color vision

Rod bipolars receive info from multiple rods, larger RF

Vision in the dark is therefore less sharp