Module 1D

Question 1

Name the main parts of the eye.

Answer 1

Cornea, Iris, Pupil, Lens, Retina, Optic nerve, Blind spot.

Question 2

List the functions of the parts of the eye.

Answer 2

Cornea - refracts light
Iris - controls how much light enters the pupil
Lens - focuses light onto retina
Retina - contains light receptors that are sensitive to light of different colours
Optic nerve - carries impulses to the brain

Question 3

What are Rods?

Answer 3

Light receptors in the retina that are very sensitive in dim light.

Question 4

What are cones?

Answer 4

Light receptors in the retina that are sensitive to coloured light.

Question 5

What is the pathway of light through the eye?

Answer 5

Light is refracted by the cornea and the lens and is brought to focus on the retina.

Question 6

What is accommodation?

Answer 6

The elastic lens changes shape to focus light.

Question 7

What will happen if you try and look at a distant object?

Answer 7

The ciliary muscles relax allowing the suspensory ligaments. The lens becomes less rounded and less light is refracted.

Question 8

What will happen if you try and look at a close object?

Answer 8

The ciliary muscles contract allowing the suspensory ligaments to slacken. The lens becomes more rounded and more light is refracted.

Question 9

How is someone long sighted?

Answer 9

The lens is the wrong shape and doesn’t bend the light enough or the eyeball is too short. This causes the image of a near object to be brought to focus behind the retina.

Question 10

What type of lens will correct long sightedness?

Answer 10

CONVEX

Question 11

How is someone short sighted?

Answer 11

The lens is the wrong shape and it bends the light too much or the eyeball is too long. This causes the image of a distant object to be brought into focus in front of the retina.

Question 12

What type of lens will correct short sightedness?

Answer 12

CONCAVE

Question 13

How is red-green colour blindness caused?

Answer 13

Lack of certain specialised cone cells in the retina.

Question 14

What is the advantage of binocular vision?

Answer 14

It will help to judge distances. The brain will compare the image that the optic nerve sends it from each eye. The more similar the images the further away the object is.

Question 15

What does the CNS consist of?

Answer 15

The brain and the spinal cord.

Question 16

What does the PNS consist of?

Answer 16

The nerves and ganglia outside of the brain and spinal cord.

Question 17

What is nerve impulse?

Answer 17

An electrical signal that is carried by neurones.

Question 18

Describe reflex reactions.

Answer 18

Fast, automatic and protective responses.

Question 19

Name the parts of a simple motor neurone?

Answer 19

Cell body, Dendrite, Axon, Sheath, Synapse

Question 20

How are neurones adapted to their function?

Answer 20

Dendrites allow them to connect with lots of other neurones.
The sheath along the axon acts as an electrical insulator which speeds up the electrical impulse.

Question 21

What is the gap between neurones called?

Answer 21

A synapse

Question 22

Describe (step by step) a simple reflex arc.

Answer 22

Stimulant 
Receptor
Sensory neurone
Relay neurone
Motor neurone 
Effector

Question 23

Explain how impulses trigger a response in a neurone.

Answer 23

The electrical impulses trigger the release of transmitter chemicals that are then able to diffuse across the synapse.
These transmitter chemicals then bind to the receptor molecules in the membrane of the next neurone.
This sets off another electrical impulse.