the eye and retina

Question 1

what is the function of eye in terms of retina?

Answer 1

focus image on retina

Question 2

what is the function of iris and pupil

Answer 2

limit amount of light passing through eye

Question 3

what is the role of cornea and lens

Answer 3

focus light on retina
cornea 80% focussing power
lens 20% focussing power but can change shape

Question 4

why does lens fatten

Answer 4

focus on close objects

Question 5

why does lens thin

Answer 5

focus on far away objects

Question 6

what happens with myopia?

Answer 6

light is focussed in front of retina

light bends too much or eye is too long

Question 7

what happens with hyperopia

Answer 7

light focused behind retina

light not bend enough or eye too short

Question 8

myopia=

Answer 8

near sightedness

Question 9

hyperopia=

Answer 9

far sightedness

Question 10

what are photo receptors

Answer 10

light sensitive cells

Question 11

what is the role of photo receptors

Answer 11

carry out transduction
transforms light into electrical impulses
visual photo pigments react to light and trigger electrical signals

Question 12

2 types of photo receptors

Answer 12

rods

cones

Question 13

number of rods and cones in retina

Answer 13

rods 120 mil

cones 6 mil

Question 14

where are rods and cones in retina

Answer 14

rods peripheral of fovea
none in blind spot

cones only in fovea
none in blind spot

Question 15

when are rods most useful and why

Answer 15

at night

very sensitive so respond well to dim light

Question 16

when are cones most useful and why

Answer 16

daylight

less sensitive

Question 17

define scotopic, photopic and mesopic

Answer 17

scotopic only rods active
photopic only cones active
mesopic rods and cones active

Question 18

what is dark adaptation

Answer 18

after time in dark, sensitivity 100,000 times greater than in light

Question 19

what are cones responsible for?

Answer 19

colour vision

Question 20

what do rods produce?

Answer 20

monochromatic vision

Question 21

what is the purkinje shift

Answer 21

red looks darker than green at night

rods respond best to green light so looks brighter and lighter than red

Question 22

define convergence

Answer 22

one neuron recieves signals from other neurons

Question 23

how many rods and cones to 1 ganglion cell

Answer 23

rods 120:1

cones 6:1

Question 24

define acuity and what determines it

Answer 24

ability to detect fine details of a stimulus
high= can detect fine details
low= can detect course details

neural convergence impacts it, greater convergence= lower acuity

Question 25

rods and cones have high or low acuity

Answer 25

rods low

cones high