Topic 2 – Cells and Control-The Eye

Question 1

outline structure and function of the cornea

Answer 1

transparent outer covering of eye

refracts light entering eye

Question 2

outline structure and function of iris

Answer 2

pigmented ring of circular muscles and radial muscles

controls size of pupil to alter how much enters eye

Question 3

what is pupil?

Answer 3

hole in iris centre that allows light rays to enter eye

Question 4

outline structure and function of lens

Answer 4

transparent, biconvex structure
suspensory ligaments attach lens to ring of ciliary muscle
refracts light, focusing onto retina

Question 5

what is function of ciliary muscles and suspensory ligaments?

Answer 5

changes shape of lens (accommodation) to focus light onto retina

Question 6

outline structure and function of retina

Answer 6

light sensitive layer composed of rod and cone cells

converts light energy into neural signals which are sent to brain via optic nerve

Question 7

what are rod cells?

Answer 7

cells in retina that are sensitive to low light intensity (dim light)

Question 8

what are cone cells?

Answer 8

cells found in retina that are sensitive to high light intenisty and can detect different colours

Question 9

what is function of optic nerve?

Answer 9

transmits nerve impulses to brain from retina.

Question 10

describe how dim light affects size of pupil?

Answer 10

light receptors detect dim light
circular muscles relax
radial muscles contract
pupil dilates
more light enters pupil

Question 11

describe how bright light affects size of pupil?

Answer 11

light receptors detect bright light
circular muscle contract
radial muscles relax
pupil contracts
less light enters pupil

Question 12

why is iris reflex important?

Answer 12

prevents bright light from damaging retina

Question 13

what is accommodation?

Answer 13

process by which elastic lens change its shape to focus on distant objects
light is focused onto the retina

Question 14

describe how eye focuses on close objects

Answer 14

close object
ciliary muscles contract
suspensory ligaments slacken
lens become more round
light is more refracted
light rays focus onto retina

Question 15

describe how eye focuses on distant objects

Answer 15

distant object
ciliary muscles relax
suspensory ligaments tighten
lens less round
light is refracted less
light rays focused onto retina

Question 16

what is long sightedness?

Answer 16

can focus on distant objects clearly

cannot focus on near objects

Question 17

what are causes of long sightedness?

Answer 17

eyeball too short

lens is less elastic, so light ray are not focused onto retina, instead behind the retina/

Question 18

how is long sightedness treated?

Answer 18

using convex lens
replacement lenses
laser eye surgery

Question 19

what is short sightedness

Answer 19

can focus on near objects clearly

cannot focus on distant objects

Question 20

what are causes of short sightedness

Answer 20

eyeball to long

lens too thick and too rounded, so light ray are not focused onto retina, so focus in front of retina

Question 21

how is short sightedness treated?

Answer 21

using concave lens
replacement lenses
laser eye surgery

Question 22

what are cataracts?

Answer 22

cloudy patch forms on lens of eye which affects vision

vision becomes blurry, difficult to see intensity of colour, problem with glare.

Question 23

how are cataracts treated?

Answer 23

clouded lens exchanged for a synthetic lens during surgery.

Question 24

what is colour blindness?

Answer 24

deficiency of eye that makes it hard to distinguish between colours
individuals with red green colour have difficulty differentiating red and green

Question 25

what is cause of colour blindness

Answer 25

damage to cone cells in retina