B3.1 The Nervous System - Structure, function & Synapses

Question 1

What is the function of the nervous system?

Answer 1

To detect changes in the environment and respond to these changes to maintain homeostasis.

Question 2

State the name given to a change in environment

Answer 2

Stimulus

Question 3

Name the group of cells responsible for detecting a stimulus?

Answer 3

Sensory receptors

Question 4

Where are receptor cells generally found?

Answer 4

Sense organs

Question 5

List some common examples of sense organs an their stimulus.

Answer 5

• Eye - Light
• Tongue - Chemical tastes (in food and drink)
• Nose - Chemical smells (in the air)
• Skin - Temperature, pressure and pain
• Ears - Sound

Question 6

What is the name given to the cells that carry out the response?

Answer 6

Effectors

Question 7

State the two types of effectors giving an example response for each.

Answer 7

1. Muscles - respond by contracting
2. Glands - respond by secretions

Question 8

State the two key components of the nervous system.

Answer 8

• Central nervous system (CNS)
• Peripheral nervous system (PNS)

Question 9

State the key components of the nervous system.

Answer 9

• Brain
• Spinal cord
• Nerves

Question 10

Define the central nervous system.

Answer 10

• The CNS is composed of the brain and spinal cord
• The brain is only involved in voluntary actions
• The spinal cord is invovled in both voluntart and involuntary actions

Question 11

Define the peripheral nervous system.

Answer 11

• The PNS is composed of the nerve cells that carry information to and from the CNS

Question 12

List the three main types of nerve cell including their pathway.

Answer 12

1. Sensory – The neurones that carry information as electrical impluses from the receptors in the sense organs to the CNS
2. Relay – The neurones that carry electrical impulses from sensory neurones to motor neurones. They are found in the CNS.
3. Motor – The neurones that carry electrical impulses from the CNS to the effectors

Question 13

What is meant by the direction of impulse?

Answer 13

• The direction in which a signal travels through a nerve

Question 14

What type of signal is transmited by the nervous system?

Answer 14

Electrical

Question 15

State the difference between a nerve and a neurone.

Answer 15

• Neurones are specialized cells that conduct electrical impulses through the body.
• A nerve is a bundle of many nerve fibres enclosed within a protective sheath.
• Nerve fibres are the long axons of neurones together with any associated tissues.

Question 16

Write out a pathway for a ‘voluntary action’.

Answer 16

Stimulus → Receptor cells → Sensory neurone → Spinal cord → Brain → Spinal cord → Motor neurone → Effector → Response

Question 17

What is menat by a ‘coordinated’ response?

Answer 17

The ability of the brain to process information from many sensory receptors simultaneously and send a series of impulses to different parts of the body to produce the required actions.

Question 18

State the direction of impulse through the neurone with reference to labels.

Answer 18

Impulse travels from the dendrites through neurone to axon terminals

Question 19

Name and label the neurone

Answer 19

Motor neurone

1. Dendrites
2. Cell body
3. Axon
4. Axon terminals

Question 20

Name the cell type that surrounds the axon of certain neurones and their purpose.

Answer 20

• Cell type - Schwann’s cells
• Collectively they form the myelin sheath
• The myelin sheath insulates the axon and increase the speed of transmission
• Gaps between these cells = nodes of Ranvier

Question 21

Where would you expect to find a synapse?

Answer 21

Between the axon terminals of the pre-synaptic neurone, and the dendrites of the post-synaptic neurone.

Question 22

What is another term given to the gap between the axon terminals of the pre-synaptic neurone and the dendrites of the post-synaptic neurone.

Answer 22

Synaptic cleft.

Question 23

Name to mode of transmission within a synaptic cleft.

Answer 23

Chemical.

Question 24

Explain the pathway of transmision from axon terminals pre-synaptic neurone to post-synaptic neurone.

Answer 24

1. Electrical signal arrives at axon terminals of the pre-synaptic neurone.
2. Vesicles containing neurotransmitters stimulated.
3. Neurotransmitters difuse out of pre-synaptic neurone into synaptic cleft.
4. Neurotransmitters difuse across synaptic cleft.
5. Neurotransmitters difuse into dendrites of the post-synaptic neurone
6. Electrical signal triggered by neurotransmitters in the post-synaptic neurone

e.g electrical → chemical → electrical

Question 25

Which organelle would you expect in abundance in the neurones?

Answer 25

Mitochondria to provide energy.

Question 26

Describe the difference in a voluntary and reflex action.

Answer 26

• Voluntary actions involve conscious thought
• Reflex actions are automatic (involuntary) reactions, they are unconscious missing out the brain, occuring without thinking.

Question 27

State the reflex that protects the retina in changing light intensities

Answer 27

Pupil reflex

Question 28

Explain how your body responds to stepping on a sharp stone from stimulus to response.

Answer 28

1. Stimulus - stepping on stone
2. Receptor - pressure receptors in the skin
3. Electrical impulse transmitted through sensory neurone to spinal cord
4. Electrical impulse transmitted through motor neurone to muscles in thigh of the leg.
5. Effector - the muscles in thigh of the leg lift the leg to move away from the object in response.

Question 29

Identify the 3 neurones (left to right).

Answer 29

1. Motor
2. Relay
3. Sensory