topic 6 the eye

Question 1

what are the light receptors in the eye called?

Answer 1

photoreceptors

Question 2

what does the cornea do?

Answer 2

transparent lens that refracts light as it enters the eye

Question 3

what does the iris do?

Answer 3

controls the amount of light entering the pupil using muscles

Question 4

what does the lens do?

Answer 4

transparent disc that changes shape to focus light onto the retina

Question 5

what does the retina do?

Answer 5

contains light receptor cells- rods and cones

Question 6

what does the optic nerve do?

Answer 6

is a sensory neuron which sends impulses from the retina to the brain

Question 7

what does the pupil do?

Answer 7

hole that allows light to enter the eye

Question 8

where is the blind spot?

Answer 8

where the optic nerve leaves the eye and there are no photoreceptor cells, so it is not sensitive to light

Question 9

what is the fovea?

Answer 9

part of the retina with lots of photoreceptors

Question 10

what pigment does a rod cell contain?

Answer 10

rhodopsin

Question 11

what pigment does a cone cell contain?

Answer 11

iodopsin

Question 12

what does a breakdown in pigment cause?

Answer 12

a generator potential

Question 13

when does rhodopsin breakdown?

Answer 13

in dim light

Question 14

when does iodopsin breakdown?

Answer 14

in bright light

Question 15

are rod cells or cone cells more sensitive?

Answer 15

rod

Question 16

how are rod cells sensitive to light?

Answer 16

distinguish between light and dark under dim light

not colour images

Question 17

how are cone cells less sensitive to light?

Answer 17

senstitive to different wavelengths of light
red sensitive/blue sensitive/green sensitive
combined effect means light of all wavelengths can be observed

Question 18

what is sensitivity?

Answer 18

the amount of light required to stimulate the receptor

Question 19

what is visual acuity?

Answer 19

the ability to distinguish between 2 different points of light

Question 20

how does the brain form an image?

Answer 20

receptors are hit by light so are stimulated
sends impulses to the brain
interpret impulse pattern as an image

Question 21

how are rods/cones connected to the brain?

Answer 21

synapses connect rods/cones to bipolar neurons
connect to ganglion cells via synapses
these have axons, which extend to the optic nerve, which connects to the brain

Question 22

why do rod cells have low visual acuity?

Answer 22

multiple connect to single bipolar cells
brain cannot interpret which impulses are sent by specific rods
only one impulse is sent
brain only gets a general understanding of vision being light or dark

Question 23

why do cone cells have high visual acuity?

Answer 23

single cone cell is connected to a single bipolar cell
brain can interpret different spots of light
receives information about colour detected and where light is
knows which bipolar cell connects to which cone cell

Question 24

how does summation occur in rod cells?

Answer 24

single rod cell stimulated unlikely to provide a large enough generator potential to stimulate nerve impulses
when a group is stimulated, combined generator potentials are enough to reach the threshold
stimulates bipolar cell to conduct nerve impulses towards the optic nerve
summation allows sight in dimmer light

Question 25

where are rod cells located?

Answer 25

retina

Question 26

where are cone cells located?

Answer 26

fovea