eyes

Question 1

Rod cells

Answer 1

• Concentrated at periphery of retina
• contains rhodopsin pigment
• connected in groups to one
  bipolar cell (retinal
  convergence)
• do not detect colour

Question 2

Cone cells

Answer 2

• Concentrated on the fovea , fewer at periphery of retina
• 3 types of cones containing
  different iodopsin pigments
• one cone connects to one
  neurone
• detect coloured light

Question 3

Rods and cones:
describe
differences in
sensitivity to light

Answer 3

Rods are more sensitive to light
cones are less sensitive to light

Question 4

Rods and cones:
describe
differences in
visual acuity

Answer 4

Cones give higher visual acuity
rods have a lower visual acuity

Question 5

Visual acuity

Answer 5

Ability to distinguish between
separate sources of light
a higher visual acuity means
more detailed, focused vision

Question 6

Rods and cones:
describe
differences in
colour vision

Answer 6

Rods allow monochromatic
vision (black and white)
cones allow colour vision

Question 7

Why rods have
high sensitivity
to light

Answer 7

Rods are connected in groups to
one bipolar cell
retinal convergence
spatial summation

stimulation of each individual-
cell alone is sub-threshold but

because rods are connected in
groups more likely threshold
potential is reached

Question 8

Why cones have
low sensitivity
to light

Answer 8

One cone joins to one neurone
no retinal convergence / spatial
summation
higher light intensity is
required to reach the threshold
potential

Question 9

Why rods have
low visual
acuity

Answer 9

• Rods connected in groups to
  one bipolar cell

retinal convergence
spatial summation

• many neurones only generate 1
  impulse / action potential ->
  cannot distinguish between
  separate sources of light

Question 10

Why cones
have high
visual acuity

Answer 10

One cone joins to one neurone
2 adjacent cones are
stimulated, brain receives 2
impulses
can distinguish between
separate sources of light

Question 11

Why rods have
monochromatic
vision

Answer 11

One type of rod cell
one pigment (rhodopsin)

Question 12

Why cones give
colour vision

Answer 12

3 types of cone cells with
different optical pigments
which absorb different
wavelengths of light
red-sensitive, green-sensitive
and blue-sensitive cones
stimulation of different
proportions of cones gives
greater range of colour
perception