The Eye

Question 1

What is at the back of the eye?

Answer 1

The retina

Question 2

What is the retina?

Answer 2

This layer contains light sensitive cells that can detect light and send impulses to the brain resulting in the formation of an image.

Question 3

What are the two types of light receptive cells called?

Answer 3

Rods
Cones

Question 4

What is the difference between rods and cones?

Answer 4

Rods can detect light, not colour whereas cones can detect colour

Question 5

What controls the amount of light entering the eye?

Answer 5

The iris

Question 6

How does the Iris control the amount of light entering the eye?

Answer 6

The muscles in the iris adjust the size of the pupil

Question 7

What do circular muscles do in pupil constriction?

Answer 7

Contract

Question 8

What do radical muscles do in pupil constriction?

Answer 8

Relax

Question 9

What do circular muscles do in pupil dilation?

Answer 9

Relax

Question 10

What do radical muscles do in pupil dilation?

Answer 10

Contract

Question 11

The control of pupil size is a … …. Which involves …. …. …. …. …. …. …. ….

Answer 11

Reflex action which involves motor neurons of the automatic nervous system

Question 12

Outline the structure and function of the cornea

Answer 12

Transparent outer covering of the eye
Refracts light entering the eye

Question 13

Outline the structure and function of the iris

Answer 13

Pigmented ring of circular muscles and radical muscles
Controls the size of the pupil to alter how much light enters the eye

Question 14

What is the pupil?

Answer 14

A hole in the iris centre that allows light rays to enter the eye

Question 15

Outline the structure and function of the lens

Answer 15

Transparent, bi-convex structure
Suspensory ligaments attach the lens to a ring of ciliary muscle
Refracts light, focusing it into the retina

Question 16

What is the function of the ciliary muscles and suspensory ligaments?

Answer 16

Change the shape of the lens (accommodation) to focus light onto the retina

Question 17

Outline the structure and function of the retina

Answer 17

Light sensitive layer composed of rod and cone cells
Converts light energy into neural signals which are sent to the brain via the optic nerve

Question 18

What are rod cells?

Answer 18

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

Question 19

What are cone cells?

Answer 19

Cells found in the retina that are sensitive to high light intensity (bright light) and can detect different colours

Question 20

What is the function of the optic nerve?

Answer 20

It transmits nerve impulses to the brain from the retina

Question 21

Describe how dim light affects the size of the pupil (5)

Answer 21

Light receptors detect dim light
Circular muscles relax
Radical muscles contract
Pupil dilates
More light enters the pupil

Question 22

Describe how bright light affects the size of the pupil (6)

Answer 22

Light receptors detect bright light
Circular muscles contract
Radical muscles relax
Pupil contracts
Less light enters the pupil

Question 23

Why is the iris reflex important?

Answer 23

It prevents bright light from damaging the retina

Question 24

What is accommodation?

Answer 24

Process by which the elastic lens change sits shape (with the aid of ciliary muscles and suspensory ligaments) to focus on near or distant objects
Light is focused onto the retina

Question 25

Describe how the eye focuses on near objects (6)

Answer 25

Near object Ciliary muscles contract Suspensory ligaments slacken Lens become more convex (more rounded ) Light is refracted more Light rays focuses onto the retina

Question 26

Convex

Answer 26

Rounded

Question 27

Describe how the eye focuses on distant objects (6)

Answer 27

Distant objects Ciliary muscles relax Suspensory ligament tighten Lens become less convex (less rounded) Light is refracted less Light rays focused onto the retina

Question 28

What is long-sightedness?

Answer 28

Can focus on distant objects clearly but cannot focus on near objects

Question 29

What are the causes of long-sightedness? (3)

Answer 29

Eyeball is too short Lens is less elastic (usually age-related) Therefore light rays are not focussed onto the retina, instead of converging behind the retina

Question 30

How is long-sightedness treated? (3)

Answer 30

Using a convex lens (causes light rays to converge) in glasses or contact lenses Replacements lenses Laser eye surgery

Question 31

What is short-sightedness?

Answer 31

Can focus on near objects clearly, cannot focus on distant objects

Question 32

What are the causes of short-sightedness? (3)

Answer 32

Eyeball is too long Lens is too thick and too rounded Therefore light rays are not focussed onto the retina instead converging in front of the retina

Question 33

How is short-sightedness treated? (3)

Answer 33

Using a concave lens (causes light rays to diverge) in glasses or contact lenses Replace,ent lenses Laser eye surgery

Question 34

What are cataracts ? (2)

Answer 34

A cloudy patch forms on the lens of the eye which negatively affects vision Vision becomes blurry, difficult to see the intensity of colours, problems with glare etc.

Question 35

How are the cataracts treated?

Answer 35

The clouded lens is exchanged for a synthetic lens during surgery

Question 36

What is colour-blindness?

Answer 36

A deficiency of the eye that makes it difficult to distinguish between colours

Question 37

What is the cause of colour-blindness?

Answer 37

Damage to cone cells in the retina