2.10.9 The Human Eye

Question 1

What is the human eye

Answer 1

The eye is a highly specialised sense organ containing receptor cells that allow us to detect the stimulus of light

Question 2

The retina of the eye contains two types of receptor cells, what are they?

Answer 2

Receptor cells that are sensitive to light, known as rods, and receptor cells that can detect colour, known as cones

Question 3

Name the 10 parts of the eye

Answer 3

Cornea 
Iris
Pupil
Lens
Ciliary Muscle
Suspensory Ligment
Sclera
Retina
Fovea
Optic Nerve

Question 4

What is the function of the cornea

Answer 4

Transparent lens that refracts light as it enters the eye

Question 5

What is the function of the Iris

Answer 5

Controls how much light enters the pupil

Question 6

What is the function of the lens

Answer 6

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

Question 7

What is the function of the retina

Answer 7

Contains light receptor cells - Rods (detect light intensity) and cones (detect colour)

Question 8

What is the role of the optic nerve

Answer 8

Sensory neurone that carries impulses between the eye and the brain

Question 9

What is the function of the pupil

Answer 9

Hole that allows light to enter the eye

Question 10

What is the function of the Ciliary muscle

Answer 10

A ring of muscle that contracts and relaxes to change the shape of the lens

Question 11

What is the function of the suspensory ligaments

Answer 11

ligaments that connect the ciliary muscle to the lens

Question 12

What is the function of the sclera

Answer 12

the strong outer wall of the eyeball that helps to keep the eye in shape and provides a place of attachment for the muscles that move the eye

Question 13

What is the function of the fovea

Answer 13

a region of the retina with the highest density of cones (colour detecting cells) where the eye sees particularly good detail

Question 14

What is the function of the aqueous humour

Answer 14

the watery liquid between the cornea and the lens

Question 15

What is the role of the vitreous humour

Answer 15

the jelly-like liquid filling the eyeball

Question 16

What is the function of the choroid

Answer 16

a pigmented layer of tissue lining the inside of the sclera that prevents the reflection of light rays inside the eyeball

Question 17

What is the function of the blind spot

Answer 17

the point at which the optic nerve leaves the eye, where there are no receptor cells

Question 18

The way the lens brings about fine focusing is called, what?

Answer 18

accommodation

Question 19

The lens is elastic and its shape can be changed when, what?

Answer 19

the suspensory ligaments attached to it become tight or loose

Question 20

The changes are brought about by

Answer 20

by the contraction or relaxation of the ciliary muscles

Question 21

When an object is close up, what happens

Answer 21

1. The ciliary muscles contract (the ring of muscle decreases in diameter)

Question 22

When an object is far away, what happens

Answer 22

1. The ciliary muscles relax (the ring of muscle increases in diameter)

Question 23

What is the pupil reflex

Answer 23

a reflex action carried out to protect the retina from damage

Question 24

In dim light, what happens to the pupil

Answer 24

the pupil dilates (widens) in order to allow as much light into the eye as possible to improve vision

Question 25

In bright light, what happens to the pupil

Answer 25

the pupil constricts (narrows) in order to prevent too much light from entering the eye and damaging the retina

Question 26

Exam Tip

Answer 26

The focusing of the eye on distant and near objects is complex and it can be hard to remember what is happening. This is something you can work out in an exam if you have forgotten – staring at your hand right in front of your eye will make your eyes feel tight and tired after a few seconds. This is because the ciliary muscles are contracted. Staring at an object far away feels relaxing and comfortable because the ciliary muscles are relaxed.