Lecture 7 - Rods and Cones

Question 1

pigment epithelium

Answer 1

is that layer right behind the retina

Enzymes necessary for pigment regeneration are found in i

Question 2

Based on dark-adapted sensitivity experiments using the
method of adjustment, what kind of receptors was found to
have the lowest absolute threshold?

Answer 2

Rods

Question 3

Why rods are more sensitive in the dark than cones

Answer 3

cones become unable to continue to adapt, for the first minutes they become more sensitive but as you continue one…

rods continue to adapt in the dark, more of the rods regenerate so the retinal is reattaching to the opsin so all those millions of rods are now ready to respond to low levels of light

Question 4

Spectral Sensitivity

Answer 4

what wavelength of light that the pigments within the rod and cone will respond to?

Question 5

Rods are sensitivite to light around ___ nm

Answer 5

500

green, blue

Question 6

Cone spectral sensitivity:

Answer 6

most responsive at ~560 nm.

yellow, reds

Question 7

Purkinje shift

Answer 7

in low light conditions you’re basically using rods, not enough light present to active cone receptors (why night looks blueish/gray)

an enhanced sensitivity to shorter
wavelengths during dark adaptation when
the shift from cone to rod vision occurs.

Question 8

Vision in daylight using cones is

Answer 8

photopic vision

Question 9

Vision at night using rods is

Answer 9

scotopic vision

Question 10

why do we have these difference in rod and cone vision?

Answer 10

Difference in spectral sensitivity is due to absorption spectra of visual pigments

Question 11

In brightly lit conditions, which visual receptors seem to be most
functionally sensitive?

Answer 11

Cones

Question 12

3 different cone types

Answer 12

L-Type: red (most numerous)

S-Type: blue (fewest, weakest responding)

M-Type: Green/Yellow