The human eye

Question 1

Iris

Answer 1

Function:
- Control the amount of light entering the eye

Question 2

Pupil

Answer 2

Function:
- Allow light to enter the eye

Question 3

Ciliary muscle (the little bump)

Answer 3

Function:
- Controls thickness of lens

Question 4

Suspensory ligaments

Answer 4

Function:
- To attach lens to ciliary body

Question 5

Lens

Answer 5

Function:
- To focus light rays onto the retina

Question 6

Cornea

Answer 6

Function:
- Refract light rays into pupil

Question 7

Aqueous humour

Answer 7

Function:
- Refract light rays
- Keep eyeball firm

Question 8

Vitreous humour

Answer 8

It is a transparent jelly-like fluid

Function:
- Refract light rays
- Keep eyeball firm

Question 9

Retina

Answer 9

Function:
- Form images
- Consists of photoreceptors:
> Rods for vision in dim light
> Cones for vision in bright light

Question 10

Fovea (little protrusion at the back of the eye)

Answer 10

Function:
- Focuses images for sharpest vision
- Contains the highest concentration of cones

Question 11

Optic nerve

Answer 11

Function:
- Transmit nerve impulses from eye to brain

Question 12

Blind spot (in front of the optic nerve)

Answer 12

Function:
- Does not contain rod and cones

Question 13

Under bright light (BCCRR)

Answer 13

1. When bright light is detected by photoreceptors in retina
2. Nerve impulses are sent to the circular muscle of the iris to contract and radial muscles of iris to relax (CCRR)
3. The pupil constricts and less light enters the eye

Question 14

Under dim light

Answer 14

1. When dim light is detected by photoreceptors in the retina
2. Nerve impulses are sent to the circular muscle of iris to relax and radial muscle of iris to contract
3. The pupil dilates and more light enters the eye

Question 15

When looking at a distant object

Answer 15

1. The ciliary muscles relax, pulling on the suspensory ligament
2. This causes the suspensory ligament to become taut, pulling on the edge of the lens
3. Causing the lens to become thinner
4. Light rays from the distant object are sharply focused on the retina
5. Nerve impulses are transmitted by the optic nerve to the brain, where the brain interprets the nerve impulses, allowing the person see the distant object

Question 16

When looking at a close object

Answer 16

1. The ciliary muscle contracts, relaxing the pull on the suspensory ligament
2. This causes the suspensory ligament to slacken, relaxing the pull on the edge of the lens
3. Causing the lens to become thicker
4. Light rays from the close object are sharply focused on the retina
5. Nerve impulses are transmitted by the optic nerves to the brain, where the brain interpret the nerve impulses, allowing the person to see the close object