The Eye

Question 1

sensory receptors

Answer 1

cells or groups of cells in sense organs that respond to stimuli

Question 2

what do the receptors do

Answer 2

they convert the energy of the stimuli into electrical impulses which travel along the sensory neurons to the brain as nerve impulses

Question 3

what do nerve impulses do

Answer 3

they cause sensations in the brain, and the brain interprets these giving us the perception of light or sound

Question 4

how can you distinguish between what type of impulse it is

Answer 4

from the part of the brain that receives the impulse

Question 5

2 types of sensory receptors

Answer 5

exteroreceptors

interoreceptors

Question 6

exteroreceptors

Answer 6

respond to information from the outside if the body e.g light/sound

Question 7

interoreceptors

Answer 7

respond to information in the body’s internal environment e.g CO2 level in blood, blood pressure etc.

Question 8

the senses

Answer 8

hearing
sight 
smell
taste 
touch (pressure, cold, heat,pain)

Question 9

function of the eyelids

Answer 9

cover and protect the eyes

Question 10

function of blinking

Answer 10

spreads fluid over the surface and keeps it moist

Question 11

tear glands

Answer 11

secrete fluid to keep eyes moist, to wash away dust and bacteria

Question 12

conjunctiva

Answer 12

a thin transparent membrane that covers the front of the eye and protects it

Question 13

eye muscles

Answer 13

allow movement of the eye in the eye orbit

Question 14

what is the sclera

Answer 14

the white of the eye, a tough layer that prevents entry of light

Question 15

function of sclera

Answer 15

protects and gives shape to the eye

Question 16

what is the cornea

Answer 16

front part of the sclera that is transparent and lets light in

Question 17

what is the iris

Answer 17

coloured part of the eye in front of the lens

Question 18

function of the iris

Answer 18

muscles in the iris contract in response to changes in light intensity, this changes the size of the pupil and controls the amount of light entering the eye

Question 19

what is the pupil

Answer 19

a hole in the centre of the iris

Question 20

function of pupil

Answer 20

to allow light to enter the eye

Question 21

bright light

Answer 21

small pupil

Question 22

dim light

Answer 22

large pupil

Question 23

function of the suspensory ligaments

Answer 23

hold the lens in place (attach the lens to the ciliary body)

Question 24

lens

Answer 24

transparent, flexible body

Question 25

function of lens

Answer 25

to focus light onto the retina (changing shape)

Question 26

function of the ciliary body

Answer 26

contains the ciliary muscle which changes the shape of the lens

Question 27

chloroid

Answer 27

a layer of pigmented cells at the back of the eye containing blood vessels and melanin

Question 28

function of blood vessels

Answer 28

to supply the eye

Question 29

function of melanin

Answer 29

black pigment to absorb light and prevent reflection of light within the eye

Question 30

retina

Answer 30

innermost layer of the eye containing light-receptor cells - the cones and rods

Question 31

function of light receptor cells

Answer 31

convert light into nerve impulses

Question 32

cones

Answer 32

``` function in bright light (daylight vision) capable of colour vision (blue, red or green) ```

Question 33

rods

Answer 33

``` function in dim light (night vision) capable of black and white vision only ```

Question 34

visual pigments in cones and rods

Answer 34

Iodopsin and Rhodopsin

Question 35

vitamin A is needed for

Answer 35

synthesis of Rhodopsin

Question 36

lack of vitamin A leads to

Answer 36

night blindness

Question 37

fovea (yellow spot)

Answer 37

small area at the centre of the retina containing cones only

Question 38

function of fovea

Answer 38

the area of the sharpest, most detailed vision, most light i focused here to form images

Question 39

blind spot

Answer 39

a small region of the retina where optic nerve fibres leave the back of the eye - it does not have cones or rods and so it is not sensitive to light

Question 40

optic nerve

Answer 40

bundle of sensory nerve fibres that leave the back of the eye

Question 41

function of the optic nerve

Answer 41

carries nerve impulses from the retina to the brain - the brain interprets these impulses

Question 42

aqueous humour

Answer 42

watery solution that fills the front part of the eye

Question 43

function of aqueous humour

Answer 43

maintains the shape of the front part of the eye

Question 44

vitreous humour

Answer 44

jelly-like material that fills the back part of the eye

Question 45

function of vitreous humour

Answer 45

gives shape to the eye and supports the lens

Question 46

advantage of having 2 eyes

Answer 46

to judge distnce or give 3-D image | to increase the field of view

Question 47

2 eye defects

Answer 47

``` short sightedness (myopia) long sightedness ```

Question 48

myopia

Answer 48

unable to focus distant objects clearly

Question 49

cause of myopia

Answer 49

distance between lens and retina is too long

Question 50

correction of myopia

Answer 50

wearing diverging lens

Question 51

long sightedness

Answer 51

unable to focus near objects clearly

Question 52

cause of long sightedness

Answer 52

small eye balls or weak lens

Question 53

correction of long sightedness

Answer 53

wearing converging lens