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Explain Nerve Structure

In this worksheet, students will explain the structure and roles of motor, sensory and relay neurones, as well as the function of synapses.

'Explain Nerve Structure' worksheet

Key stage:  KS 4

GCSE Subjects:   Biology: Single Subject, Biology: Combined Science

GCSE Boards:   Pearson Edexcel

Curriculum topic:   Cells and Control

Curriculum subtopic:   Cells and Control

Difficulty level:  

Worksheet Overview

QUESTION 1 of 10

The nervous system is so important- it makes us notice danger, makes us react and protects us by using our senses!

 

 

It's made up of many individual nerve cells are called neurones, and their main function is to transport electrical signals around the body to control our internal and external processes.

 

BUT a nerve is not the same as a nerve cell, as a nerve is a BUNDLE of nerve cells packed together.

 

Now, there are 3 types of neurones: Motor, Sensory and Relay Neurones, and while they are unique, they also share some common functional adaptions too:

 

Structural Adaptions of Motor, Sensory and Relay Neurones for their Functions

Motor Neurones Sensory Neurones Relay Neurones/ Interneurons

FUNCTION:

Motor neurones carry signals from the CNS to the target organs and muscles to perform an action

 

FUNCTION: 

They detect changes in our environment, or stimuli, from loud noises to temperature changes, and carry this information from around the body to the brain or spinal cord.

FUNCTION:

They help pass information between the sensory neurones and the motor neurones.

STRUCTURE:

Neurones have a cell body with branches called dendrites which communicate with other cells.

 

The cell body leads to the axon, a long fibre that guides the signal to its destination.

 

To speed up the electrical signals, the axon is wrapped in myelin sheaths, and it’s the myelin that insulates the axon, which ends in the axon terminals of the neurone.

STRUCTURE:

Sensory neurones have specialised cells called receptors in the periphery of our bodies that detect stimuli, and so sensory cells have no dendrites.

 

Their axons are short but also insulated with myelin.

STRUCTURE:

The relay neurone can also be called an interneuron.

 

(think that it runs interference between the sensory and motor neurones!)

 

Their structure is very similar to motor neurones, although their dendrites are short and their axons can be long AND short!

 

Important Note: Dendrites are not axon terminals!!

 

Dendrites are on the cell body and axon terminals are on the other end of the neurone after the axon.

 

 

Synapses

Neurones need synapses to communicate and pass along the electrical signals, allowing the axon terminals of one nerve cell to pass on information to the dendrites of the next cell. 

 

Electrical signals can't pass through the air so in the axon terminal, it's converted into specific chemicals called neurotransmitters.

 

These pass across a gap called the synaptic cleft to the receiving receptors on the dendrites of the other cell, where they trigger another electrical signal to be passed down the axon. 

 

 

 

So let's put everything together- what happens when you touch something sharp?

 

1. Sensory receptors detect pain in the skin cells of your finger

 

2. An electrical signal is generated at the cell body and travels down the sensory axon to the axon terminals

 

3. Here the sensory axon terminals synapse with relay neuron and communicate with specific neurotransmitters

 

4. The relay neurone carries the signal to its terminals which then synapse with the motor neurone

 

5. A motor neurone then takes the electrical signal to the muscles of the finger, and makes them contract to make you move away from the stimulus.

A neurone is a...

Single nerve cell

Bundle of nerve cells

Type of receptor

Type of chemical

The 3 different types of neurones are sensory, relay and what?

Match the functions of these nerve cells:

Column A

Column B

Motor Neurone
Signal is carried from the peripheries to the brai...
Sensory Neurone
Passes on information between neurones
Relay Neurone/ Interneuron
Signal is carried from the brain or spinal cord to...

For the neurones below, indicate if they have LONG, SHORT or BOTH types of axons.

Column A

Column B

Motor Neurone
Signal is carried from the peripheries to the brai...
Sensory Neurone
Passes on information between neurones
Relay Neurone/ Interneuron
Signal is carried from the brain or spinal cord to...

Identify which adaption belongs to which nerve cell type:

Neurones are specially designed for their function.

True or False:

 

The terms 'dendrites' and 'axon terminals' are interchangeable 

When we talk about synapses, there is a gap between the two neurones where the transfer of information takes place- what is it called?

When electrical signals are converted into chemicals before they pass across the synaptic cleft, what are these chemicals called?

Look at this scenario:

 

'Susie is playing with a candle and her finger accidentally touches the hot wax'

 

What happens next?

 

Match the type of neurone- 'X'- with the action performed

 

  • Question 1

A neurone is a...

CORRECT ANSWER
Single nerve cell
EDDIE SAYS
This is a key term that many students get confused with. A NEURONE is a single nerve cell, but a NERVE is a bundle of neurones/ nerve cells!
  • Question 2

The 3 different types of neurones are sensory, relay and what?

CORRECT ANSWER
MOTOR
MOTOR NEURONE
EDDIE SAYS
The 3 key players are the motor neurones, the sensory neurones and relay neurones which are also called interneurons. Click next to practise more questions about their structure and function!
  • Question 3

Match the functions of these nerve cells:

CORRECT ANSWER

Column A

Column B

Motor Neurone
Signal is carried from the brain ...
Sensory Neurone
Signal is carried from the periph...
Relay Neurone/ Interneuron
Passes on information between neu...
EDDIE SAYS
How confident did you feel going into this question? Sensory neurones detect the stimulus or change in the environment, and their signal is carried from the peripheral nervous system to the central nervous system, which I hope you remember is the brain, brainstem and spinal cord. It's then that the motor neurones carry instructions in the form of electrical signals from the brain or spinal cord to the target organ or muscle where the stimulus occurred, creating a response. And relay neurones work between them to promote communication.
  • Question 4

For the neurones below, indicate if they have LONG, SHORT or BOTH types of axons.

CORRECT ANSWER
EDDIE SAYS
Axons are a vital part of the neurone's transport function, and each neurone has adapted it to help their individual roles: Motor neurones have very long axons, as to carry information to muscles from the brain or spine, axons like the ones from the hip to your toes need to be very long! Sensory neurones, however, have short fibres and relay neurones can actually have both long and short axons.
  • Question 5

Identify which adaption belongs to which nerve cell type:

CORRECT ANSWER
EDDIE SAYS
Clearly, being able to explain the differences and similarities between the 3 neurones is a key point of this topic and you will be asked about them to death! So, again, motor, sensory and relay cells are all neurones and share some common characteristics, but they are heavily adapted for their unique functions and so have some key structural differences. Motor neurones look like the typical neurone image and have plenty of dendrites on the cell body, though they carry instructions from the central nervous system rather than detecting stimuli so they have no receptors. Sensory neurones, however, have receptors instead of dendrites because they are the stimuli detectors and its because of the sensory receptors in sensory neurones that we notice the effects of the environment on our bodies and adapt to it, like feeling cold and raising the hairs on our arms, or sensing extreme heat and moving ourselves away.
  • Question 6

Neurones are specially designed for their function.

CORRECT ANSWER
EDDIE SAYS
Did you do as well as you hoped? Myelin sheaths are excellent insulators and stop electrical signals being carried throughout the whole axon. This speeds up the electrical signal and helps neurones work effectively.
  • Question 7

True or False:

 

The terms 'dendrites' and 'axon terminals' are interchangeable 

CORRECT ANSWER
EDDIE SAYS
This is DEFINITELY FALSE and a key point many students learn wrong early on and have trouble with later in their learning. Dendrites are on the soma of cells while axon terminals are on the other end after the axon- so one is at the head and the other is at the tail! It\'s easier to realise them as two separate things when you realise that a synapse occurs between an axon terminal and a dendrite, so they must be different as a synapse is between the end of one cell and the start of another!
  • Question 8

When we talk about synapses, there is a gap between the two neurones where the transfer of information takes place- what is it called?

CORRECT ANSWER
THE SYNAPTIC CLEFT
EDDIE SAYS
We're really getting into the fine detail of neurology now, but this is good practice for the level of understanding you should aim for to stay on track for your desired grade. For two neurones to communicate, they use synapses. And the gap between the two neurones where communication occurs is called the synaptic cleft.
  • Question 9

When electrical signals are converted into chemicals before they pass across the synaptic cleft, what are these chemicals called?

CORRECT ANSWER
NEUROTRANSMITTERS
EDDIE SAYS
How was this question for you? As electrical signals can't pass through air, when neurones synapse, the signal is converted into NEUROTRANSMITTERS which are chemicals specifically designed to be recognised and only fit the uniquely shaped receptors on the ends of the receiving dendrites of the other cell.
  • Question 10

Look at this scenario:

 

'Susie is playing with a candle and her finger accidentally touches the hot wax'

 

What happens next?

 

Match the type of neurone- 'X'- with the action performed

 

CORRECT ANSWER
EDDIE SAYS
How did you get on with this mean final question? How all the structures we've learnt about come together to perform their function is a vital takeaway concept in this topic and so practising questions like this will help you greatly in terms of your understanding. So let's run through how this all works: 1. Sensory receptors detect a stimulus 2. An electrical signal is generated at the cell body and travels down the sensory axon to the axon terminals 3. Here the sensory axon terminals synapse with relay neuron and communicate with specific neurotransmitters 4. The relay neurone carries the signal to its terminals which then synapse with the motor neurone 5. A motor neurone then takes the electrical signal to the target organs or muscles so you can perform an action in response to the stimulus So all the neurones come together to detect, act and help our bodies with safety and control. Well done on this very wordy topic and don't forget to jot down any explanations that you felt really helped you come to grips with some of the harder things when it comes to nerve structure!
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