Nervous system: eyes

Question 1

How do eyes see?

Answer 1

By sensing the light that objects give off or reflect

Question 2

What do the nerves inside the eyes do? (in relation to sight)

Answer 2

They send signals to the brain revealing objects’ shapes, sizes, colours, and distances

Question 3

What helps with depth perception ?

Answer 3

Overlapping fields of vision

Question 4

What is the purpose of eyelids and eyelashes?

Answer 4

To protect the eyes from dust and injury

Question 5

What does the conjunctiva do (a membrane)?

Answer 5

Helps the lacrimal glands lubricate each eyeball

Question 6

Cornea

Answer 6

Tough, transparent covering over the front part of the eye (convex in shape)

Question 7

Sclera

Answer 7

White dense tissue (white of the eye)

Question 8

Iris

Answer 8

Coloured part of the eye; contains muscles that contract or relax to adjust the size of the pupil

Question 9

Pupil

Answer 9

Hole in the middle of the iris

Question 10

Lens

Answer 10

Transparent, bi-convex, flexible disc behind the iris

Question 11

Suspensory ligaments

Answer 11

Attaches the lens to the ciliary body of the eye and holds the lens in place

Question 12

Ciliary muscles

Answer 12

Muscles connected to the lens by suspensory ligaments

Question 13

Retina

Answer 13

The lining at the back of the eye containing 2 types of light receptor cells

Question 14

What are the two types of light receptor cells?

Answer 14

Rods and cones

Question 15

Watery fluid of the eye

Answer 15

Aqueous humour

Question 16

Fovea

Answer 16

A depression where vision is the sharpest

Question 17

Optic nerve

Answer 17

Nerve fibres at the back of the brain

Question 18

Function of the cornea

Answer 18

Refracts light as it enters the eye (by a fixed amount)

Question 19

Function of the iris

Answer 19

Controls how much light enters the pupil

Question 20

Function of the pupil

Answer 20

Allows light to pass through as it enters the eye

Question 21

Function of the lens

Answer 21

Refracts light to focus it onto the retina (the amount of thickness can be adjusted by altering the thickness and curvature of the lens)

Question 22

Function of the ciliary muscles

Answer 22

Adjust the shape of the lens to make it more or less curved, so as to increase/decrease the refraction of light

Question 23

Function of suspensory ligaments

Answer 23

Slacken or stretch as the ciliary muscles contract or relax, to adjust to the thickness and curvature of the lens

Question 24

Function of the retina

Answer 24

Contains light receptors which trigger electrical impulses to be sent to the brain when light is detected

Question 25

Function of rods

Answer 25

They sense dim light

Question 26

Function of cones

Answer 26

They sense bright light and colours (think of multicoloured cones)

Question 27

Refraction

Answer 27

The bending of light

Question 28

What forms a blind spot in our vision?

Answer 28

The nerve's point of entry in the eyeball

Question 29

How many ocular muscles are there?

Answer 29

6

Question 30

How does the eyeball move?

Answer 30

6 ocular muscles attached to the outside of the sclera move the eyeball in different ways

Question 31

What muscles move the eye up and down?

Answer 31

Superior rectus and inferior rectus muscles

Question 32

What muscles move the eye left and right?

Answer 32

Lateral rectus and medial rectus muscles

Question 33

What muscles move the eye downwards and upwards and outwards?

Answer 33

Superior oblique and inferior oblique muscles

Question 34

How does the eye focus?

Answer 34

Inside the eye, **light rays from an object are bent** by cornea, lens, aqueous humour, and vitreous body, so that the rays come to a **focus on the retina** -the focused image is upside down, but the brain "sees it" the right way up

Question 35

How the eyes focus: distant object

Answer 35

Light rays from a distant object are bent relatively slightly inside the eye. Its lens has gently curved sides

Question 36

How the eyes focus: nearby object

Answer 36

Light rays from a nearby object must be bent more sharply to bring them into focus. The lens grows shorter and fatter, with strongly curved sides