light and the eye

Question 1

cornea

Answer 1

clear outer tissue
bends light wave

Question 2

pupil

Answer 2

light wave sent through
a hole in iris

Question 3

iris

Answer 3

muscle that controls size of pupil
contracts and relaxes

Question 4

lens

Answer 4

light hits lens
bends rays and focuses them on retina

Question 5

retina

Answer 5

light sensitive tissue lining back of eye

Question 6

accommodation

Answer 6

process by which eye maintains clear image on retina
muscles change shape of lens

muscles tighten causing lens to thicken
focus on closer objects

Question 7

ciliary muscles

Answer 7

increase focusing power by increasing curvature of lens
contract or relax

Question 8

light adaptation

Answer 8

sensory adaptation to different levels of light

Question 9

near point

Answer 9

distance at which lens cannot adjust any further for close objects

Question 10

presbyopia

Answer 10

hardening of lens
weakening of ciliary muscles
distance of near point increases with age

Question 11

hyperopia

Answer 11

farsightedness

Question 12

myopia

Answer 12

nearsightedness
cant see distant objects clearly
causes differences in eye shape

refractive myopia
cornea or lens bends too much light

axial myopia
eyeball to long

Question 13

cone cells

Answer 13

detect colour
operate in normal daylight conditions
focus on fine detail
larger but fewer
concentrated on fovea

Question 14

rod cells

Answer 14

more sensitive in low light
black and white
more numerous in peripheral
on retina, not fovea

Question 15

distribution of rods and cones

Answer 15

cones densely packed in fovea
rods distributed on retina

blind spot
contains no receptors
where optical nerve meets eye
not noticed as brain fills in space

Question 16

synaptic terminal

Answer 16

where electrical signal propagates
passed onto visual neurons

Question 17

inner segments

Answer 17

cellular structures such as ribosomes and mitochondria

Question 18

outer segments

Answer 18

contain light sensitive visual pigments
where light is transduced into energy

Question 19

components of rods and cones

Answer 19

opsin
large protein that crosses disc membrane

retinal
light sensitive molecule within disc

Question 20

isomerisatin

Answer 20

process in which retinal changes its shape due to the absorption of light
= transduction

occurs when retinal absorbs light

Question 21

spatial summation

Answer 21

simultaneous signals coming from multiple pre synaptic neuron’s received by one postsynaptic neuron
added together to reach threshold

Question 22

temporal summation

Answer 22

single presynaptic neuron rapid firing signals to postsynaptic neuron
added together to reach threshold

Question 23

light sensitivity in rod cells

Answer 23

individually rods require less light to respond
convergence of rod activity on ganglion increases likelihood of firing
allows spatial summation
cannot resolve fine detail

Question 24

visual acuity in cone cells

Answer 24

one to one wiring with ganglion cells
provides information to brain about spatial position
can see fine detail
need more light to respond to cause respond than rods