B1d

Question 1

name and describe the functions of the main parts of the eye

Answer 1

cornea - refracts light
iris - controls how much light enters the pupil
lens - focuses light onto retina
retina - contains light receptors (rods and cones), some sensitive to light of different colours
optic nerve - carries impulses to the brain

Question 2

describe the pathway of light through a normally functioning eyeball

Answer 2

it gets refracted a little by the cornea, then refracted more by the lens. it is then brought to focus on the retina

Question 3

how does the eye adjust to see a distant object

Answer 3

• ciliary muscles relax
• suspensory ligaments tighten
• lens becomes long and thin
• light is only refracted a little

Question 4

how does the eye adjust to focus on a near object

Answer 4

• ciliary muscles contract
• suspensory ligaments slacken
• lens becomes short and fat
• light is only refracted more to focus on the retina

Question 5

explain the advantages and disadvantages of monocular and binocular vision

Answer 5

• monocular vision: wider field of view but poorer
judgement of distance
• binocular vision: narrower field of view but better
judgement of distance.

Question 6

how is short sightedness and long sightedness caused

Answer 6

short sighted - eyeball is too long

long sighted - eyeball is too short

Question 7

how can we correct eye problems

Answer 7

• both: corneal laser surgery
• short sighted: concave lens to diverge the light
• long sighted: convex lens to converge the light

Question 8

what is the cause of reg-green colour blindness

Answer 8

• inherited condition

- lack of specialised cells in the retina

Question 9

name the 3 main parts of a motor neurone

Answer 9

axon, sheath and cell body

Question 10

describe the path of a reflex arc

Answer 10

Describe a reflex arc: stimulus → receptor → sensory
neurone → central nervous system → motor neurone
→ effector → response.