lecture 2

Question 1

what is the distal stimulus for vision

Answer 1

light

Question 2

physiological representation of wavelength

Answer 2

colour

Question 3

physiological representation of intensity

Answer 3

brightness

Question 4

physical properties of light

Answer 4

wavelength, intensity

Question 5

what is light

Answer 5

form of electromagnetic energy

Question 6

visible spectrum wavelength range

Answer 6

~400-700nm

Question 7

where are receptors located in the eye

Answer 7

in the retina

Question 8

function of the eye

Answer 8

to focus image onto the retina

Question 9

proximal stimulus representing light

Answer 9

retinal image

Question 10

role of the iris an pupil

How does it achieve this?

Answer 10

limit the amount of light passing through
has an adjustable aperture
allows us to deal with a great range of light intensities

Question 11

what is the diameter range for the pupil

Answer 11

2-9mm

Question 12

role of the cornea and lens

Answer 12

to focus light onto the retina

Question 13

how much focusing power does the cornea have?

Answer 13

80%

Question 14

how much focusing power does the lens have?

Answer 14

20%

Question 15

how can the lens change shape?

Answer 15

due to the actions of the ciliary muscles

Question 16

what shape is the lens when focusing a close object

Answer 16

it becomes fatter and shorter

Question 17

what shape is the lens when focusing far objects

Answer 17

thinner and longer

Question 18

myopia

Answer 18

near sightedness

light focused in front of the retina

Question 19

hyperopia

Answer 19

far-sightedness

light focussed behind the retina

Question 20

how to correct myopia

Answer 20

concave lens

Question 21

how to correct hyperopia

Answer 21

convex lens

Question 22

retina

Answer 22

photosensitive layer at the back of the eye

Question 23

role of retina

Answer 23

carry out transduction, transform light into electrical impulses

Question 24

cells in the eye from front to back

Answer 24

photoreceptors
(horizontal cells) 
bipolar cells 
(amacrine cells) 
retinal ganglion cells 
optic nerve

Question 25

what must light pass through to reach photoreceptors?

Answer 25

blood vessels, cells and axons

Question 26

where are receptors?

Answer 26

layer furthest from incoming light

Question 27

how does transduction occur in the eye?

Answer 27

visual photopigments reacting to light and triggering electrical signals

Question 28

what is the action of a change in the shape of the lens called?

Answer 28

accommodation

Question 29

how many rods are there?

Answer 29

120 million

Question 30

when are rods most useful?

Answer 30

most useful at night, useless during the day

Question 31

what type of vision do rods produce?

Answer 31

monochromatic

Question 32

how sensitive are rods?

Answer 32

very sensitive

Question 33

what light do rods respond well to?

Answer 33

dim light

Question 34

how many types of rods are there?

Answer 34

one

Question 35

what wavelength do rods respond best to?

Answer 35

medium wavelengths (green light)

Question 36

what is the purkinje shift

Answer 36

at night red looms darker than green

Question 37

what causes the purkinje shift?

Answer 37

rods respond to green light

Question 38

how many cones in the human eye?

Answer 38

6 million

Question 39

are cones more or less sensitive than rods?

Answer 39

less sensitive

Question 40

when do cones ework best?

Answer 40

work best during the day, useless at night

Question 41

what are cones responsible for?

Answer 41

colour vision

Question 42

how many types of cones are there? what are they?

Answer 42

three types: red, green, blue

Question 43

what wavelength do red cones respond best to?

Answer 43

long wavelengths

Question 44

what wavelength do green cones respond best to?

Answer 44

medium wavelengths

Question 45

what wavelength do blue cones respond best to?

Answer 45

short wavelengths

Question 46

what receptors are active during scotopic vison?

Answer 46

only rods

Question 47

what receptors are active during photopic vision

Answer 47

only cones

Question 48

what receptors are active during mesopic vision?

Answer 48

both rods and cones are active?

Question 49

what light intensities/ times of day does mesopic vision cover?

Answer 49

full moon/ bright moonlight to early twilight

Question 50

what effect doe bright light have on photoreceptors?

Answer 50

bleaches photopigments causing them to stop responding

Question 51

what is dark adaption?

Answer 51

increase in eyes sensitivity in the dark

Question 52

how many times greater is eyes sensitivity after 20-30 minutes in the dark?

Answer 52

approximately 100,000 times greater than sensitivity in the light

Question 53

what photoreceptors are concentrated on the fovea?

Answer 53

cones

Question 54

convergence

Answer 54

one neuron receives signals from many other neurons

Question 55

what receptors does the peripheral contain?

Answer 55

a large amount of rods | a small amount of cones

Question 56

what is the blind spot

Answer 56

an area on the retina that contains no rods and no cones

Question 57

convergence of rod cells

Answer 57

120 rod cells to 1 ganglion cell

Question 58

convergence of cone cells

Answer 58

6 cone cells to 1 ganglion cell

Question 59

acuity

Answer 59

the ability to detect fine details of a stimulus

Question 60

high acuity

Answer 60

can detect fine details

Question 61

low acuity

Answer 61

can detect only course details

Question 62

do rods or cones have a higher acuity? why?

Answer 62

cones have a higher acuity due to less convergence

Question 63

where is the highest acuity in the retina?

Answer 63

the fovea

Question 64

where does acuity decrease?

Answer 64

toward the peripheral/ away from the fovea | in low lighting conditions (scotopic)

Question 65

what ensures fovea is focussed on the fovea/ high acuity?

Answer 65

eye movements