4.5.2 - Nervous System: 4.5.2.3 - The Eye

Question 1

What is the eye?

Answer 1

The eye is a sense organ containing receptors sensitive to light intensity
and colour.

Question 2

What are receptors?

Answer 2

Groups of specialised cells that can generate an electrical impulse in a sensory neurone.

Question 3

What are the two types of receptor cells in the eye?

Answer 3

• Rod cells: sensitive to light intensity

- Cone cells: sensitive to different wavelengths of visible light (colour)

Question 4

What is the purpose of the eye?

Answer 4

To receive light and focus it onto the retina at the back of the eye

Question 5

Function of cornea?

Answer 5

Transparent lens that refracts (bends) light as it enters the eye.

Question 6

Function of iris?

Answer 6

Controls how much light enters the pupil.

Question 7

Function of lens?

Answer 7

Transparent disc that can change shape to focus light onto the retina.

Question 8

Function of retina?

Answer 8

Enables vision, receives light from lens, converts it to neural signals & transmits them to brain for visual recognition.

Question 9

Function of optic nerve?

Answer 9

Sensory neurone that carries impulses between eye and brain.

Question 10

Function of pupil?

Answer 10

Hole that allows light to enter the eye.

Question 11

Function of sclera?

Answer 11

Provides support for the eyeball, helping it change shape.

Question 12

Function of ciliary muscles?

Answer 12

Produces fluid in eye called aqueous humor, changes shape of lens when eyes focus on near objects (accommodation).

Question 13

Function of suspensory ligaments?

Answer 13

Hold lens in place & control its shape.

Question 14

What is accommodation?

Answer 14

The process of changing the shape of the lens to focus on near or distant objects.

Question 15

Describe the process of accommodation

Answer 15

When focusing on a distant object:

• the ciliary muscle relaxes & its diameter becomes wider
• the suspensory ligaments tighten
• the lens gets thinner - refracting light less

When focusing on a near object:

• the ciliary muscles contract & diameter gets smaller
• suspensory ligaments loosen
• lens becomes thicker & more curved - refracting light more

Question 16

What is myopia?

Answer 16

Short-sightedness:

• Lens is too thick and curved, so light is focused in front of the retina.
• Eyeball is too long, so the distance between the lens & the retina is too great.
• Distant objects look blurry.

Question 17

What is hyperopia?

Answer 17

Long-sightedness:

• Lens is too flat so rays of light don’t focus on the retina.
• Eyeball is too short, so the distance between the retina and the lens is too small.
• Near objects look blurry.

Question 18

What are some treatment methods for myopia and hyperopia?

Answer 18

• Glasses
• Contact lenses
• Laser eye surgery
• Replacement lens (for hyperopia)

Question 19

What lens is used to correct myopia?

Answer 19

Concave

Question 20

What lens is used to correct hyperopia?

Answer 20

Convex

Question 21

Explain laser eye surgery

Answer 21

For Myopia:
Lasers are used to reduce thickness of cornea, so it refracts light less
For hyperopia:
They change the curvature of the lens, so it refracts light more strongly.

Question 22

What are some risks of a replacement lens?

Answer 22

• Damage to the retina

- Cataracts developing