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Understand The Nervous System

Worksheet Overview

QUESTION 1 of 10

The nervous system carries information around the body in the form of electrical impulses (messages) in cells specialised for this job -  the nerve cells. The nerve cells are called neurones. The main organs in the nervous system are the brain and the spinal cord, which make up the central nervous system (CNS). The nerves to and from the spinal cord make up the peripheral nervous system. You can see the main organs and major nerves of the human body in the diagram. It is worth noting that every space in our body is covered by nerves even if only the major ones are shown in the diagram.

 

The central and peripheral nervous system.

 

The nervous system controls voluntary and involuntary actions. The voluntary actions are the ones we think about doing first, whereas an involuntary action is called a reflex and does not happen as a result of thought - it is automatic and fast. 

 

The neurone

 

A nerve cell

 

This is a diagram of a neurone, specifically a motor neurone. Motor neurones carry signals from the CNS to effectors. Effectors are the parts of the body that perform the actions, for example muscles. As you can see, neurones have long bodies with an axon for structure, which is protected by a fatty sheath, in order to prevent chemical impulses crossing over. At either ends of the axon there are dendrites which branch out to receive or pass signals from/to other neurones or receptors (organs that recognise stimuli) and effectors.

There are two other types of neurones -  the sensory neurone that carries signals from receptors to the CNS, and the relay neurone that carries signals from one part of the CNS to another.

 

Synapse

Signals have to pass from one neurone to another. There is a gap between neurones called the synapse. When an electrical impulse approaches the synapse, it triggers the release of chemicals called neurotransmitters, such as acetylcholine. These substances diffuse across the synapse, allowing the impulse to be carried along.

 

Voluntary actions

When we want to perform an action, for example picking up our keys to leave our house, neurones carry the message to the brain and the brain sends signals to the appropriate part of the body to do this action - in our example, to lift our arm and grab our keys with our hand and fingers.

 

Reflex actions

It is important that our nervous system can perform actions without us thinking about them first in order to protect us from danger. Reflex actions are fast and automatic, as mentioned earlier, and the impulses are not carried all the way to the brain to save time. Instead, they travel only to the spinal cord and then to effectors. Here is a diagram of a reflex arc:

 

A reflex arc

 

A stimulus (sudden change in circumstances) such as touching a hot plate, is received by a pain receptor in the skin. A sensory neurone carries the information to the spinal cord and it is passed to a motor neurone through a relay neurone. The motor neurone carries the information to an effector and so we have a response, which in this case would be our hand dropping the hot plate to avoid burning.

 

Quick on to the questions!

Humans are considered the most clever of all living organisms because we have a big brain. Our head occupies a large part of our body to provide space for our big brain. Look at the picture of a stegosaurus:

 

A stegosaurus

 

Tick the sentences below that are true of this dinosaur.

It had a very small head in comparison to its body

It was a very clever dinosaur

Having a small head implies a small brain which probably means it was not very clever

It was a very weak dinosaur

What is the job of the nervous system?

It carries oxygen and glucose to all parts of the body

It provides movement to the body

It carries electrical impulses around the body

Apart from the brain (labelled A), what is the other main organ (labelled B) in the central nervous system?

 

Image of the CNS and PNS

What does the peripheral nervous system do with electrical impulses?

The nerves carry messages from the brain and the spinal cord

The messages are in the form of electrical impulses

The nerves carry blood around the body

The nerves carry oxygen around the body

Which of these options describe the functions of the nervous system?

Reflex actions to prevent us from harming ourselves

Protects us from cosmic rays

Voluntary actions, where we do something without thinking about it

Voluntary actions, where we think about something and then do it

Tick the actions below that you think are reflex actions.

Knee jerk reaction

Picking up our purse before going out

Taking a hand away from a sharp object

Eye pupils getting smaller in bright light

Complete the sentence by writing the missing words into the boxes in the table below:

 

Sensory neurones carry impulses ___A___ from a sense organ, whereas motor neurones carry impulses to an ______B_____.

 Missing Words
A
B

What is a synapse? 

A connection between a neurone and the spinal cord

A gap between two neurones that allows the electrical impulse to cross through a nerve cell

A gap between two neurones where the electrical impulse is transmitted with the aid of chemicals called neurotransmitters

What is the correct definition of a relay neurone?

A nerve cell that carries impulses away from a sense organ

A nerve cell that carries impulses from one part of the CNS to another

A nerve cell that carries impulses to an effector

The steps of the reflex arc are listed in the correct order below. However, not all of the statements are correct. Tick the wrong statements.

A stimulus is picked up by a receptor

The impulse is carried along a sensory neurone to the brain

A relay neurone passes the impulse from the brain to a motor neurone

The motor neurone carries the impulse to an effector

The effector performs its action

The effector's response protects us from danger

  • Question 1

Humans are considered the most clever of all living organisms because we have a big brain. Our head occupies a large part of our body to provide space for our big brain. Look at the picture of a stegosaurus:

 

A stegosaurus

 

Tick the sentences below that are true of this dinosaur.

CORRECT ANSWER
It had a very small head in comparison to its body
Having a small head implies a small brain which probably means it was not very clever
EDDIE SAYS
Stegosaurus weighed half a tonne and had a very small head compared to its huge body. A small head is a sign of a small brain, which means...stegosaurus was not very clever!
  • Question 2

What is the job of the nervous system?

CORRECT ANSWER
It carries electrical impulses around the body
EDDIE SAYS
Was this one alright? It really helps when you've got a choice of options to read and select from. The role of the nervous system is to carry messages in the form of electrical signals around the body. They are quick-acting signals that don't last very long.
  • Question 3

Apart from the brain (labelled A), what is the other main organ (labelled B) in the central nervous system?

 

Image of the CNS and PNS

CORRECT ANSWER
spinal cord
the spinal cord
EDDIE SAYS
A tricky one this! The CNS (central nervous system) is made up of the brain and the spinal cord. It is the part of the nervous system that controls all actions - the brain and spinal cord process all of the information from the peripheral nervous system.
  • Question 4

What does the peripheral nervous system do with electrical impulses?

CORRECT ANSWER
The nerves carry messages from the brain and the spinal cord
The messages are in the form of electrical impulses
EDDIE SAYS
This looked tricky but it was really a process of elimination. Hopefully, once you read options three and four, you were able to rule them out - it's the various blood vessels that carry blood and oxygen around the body, not nerves. Nerves make up the peripheral nervous system and carry information as electrical impulses to and from the brain and the spinal cord. They consist of motor neurones (that make things move) and sensory neurones (that carry information to the CNS).
  • Question 5

Which of these options describe the functions of the nervous system?

CORRECT ANSWER
Reflex actions to prevent us from harming ourselves
Voluntary actions, where we think about something and then do it
EDDIE SAYS
The nervous system can perform voluntary actions, which we think about before doing. They also perform reflex actions that happen quickly and automatically without having the time to think about it, such as taking your hand away from a hot surface.
  • Question 6

Tick the actions below that you think are reflex actions.

CORRECT ANSWER
Knee jerk reaction
Taking a hand away from a sharp object
Eye pupils getting smaller in bright light
EDDIE SAYS
There are many reflex actions that we have little or no control over but picking up a purse is not one of those! Pupils get bigger in dim light and smaller in bright light. This is to enable us to see better when light is reduced, and also to protect our eyes from being damaged by too much light. The knee jerk reaction is when the doctor taps us below the knee to check our reflexes. However hard you try, it isn't possible to stop your knee from jerking and kicking the doctor! Finally, just as when you touch a hot plate, touching a sharp object by mistake triggers a reflex response to avoid hurting yourself. The body is programmed to protect itself!
  • Question 7

Complete the sentence by writing the missing words into the boxes in the table below:

 

Sensory neurones carry impulses ___A___ from a sense organ, whereas motor neurones carry impulses to an ______B_____.

CORRECT ANSWER
 Missing Words
A
B
EDDIE SAYS
How did you get on with this one? It's important not to muddle up your neurones, so if you're a bit confused, why not go back and have another look at the Introduction. Sensory neurones carry impulses away from a sense organ, such as the skin on your hand touching the hot plate. Motor neurones, however, carry impulses to an effector, such as a muscle. So, in the hot plate example, a motor neurone sends a message to the muscles in your arm making you move your hand away.
  • Question 8

What is a synapse? 

CORRECT ANSWER
A gap between two neurones where the electrical impulse is transmitted with the aid of chemicals called neurotransmitters
EDDIE SAYS
A synapse is a gap between two neurones where the electrical impulse is transmitted across with the aid of chemicals called neurotransmitters. This is where drugs like pain killers do their work - they stop signals from being sent across the synapse.
  • Question 9

What is the correct definition of a relay neurone?

CORRECT ANSWER
A nerve cell that carries impulses from one part of the CNS to another
EDDIE SAYS
A relay neurone is a nerve cell that carries impulses from one part of the CNS to another. It is normally involved in autonomic reactions - but the brain is made up of billions of relay neurones. Nearly at the end of this challenging activity.
  • Question 10

The steps of the reflex arc are listed in the correct order below. However, not all of the statements are correct. Tick the wrong statements.

CORRECT ANSWER
The impulse is carried along a sensory neurone to the brain
A relay neurone passes the impulse from the brain to a motor neurone
EDDIE SAYS
Wow, this was tricky wasn't it? Did you find yourself ticking the ones that were correct instead of the incorrect ones? This shows just how important it is to read the questions really carefully. This is the correct order: A stimulus is picked up by a receptor. The impulse is carried along a sensory neurone to the spinal cord (not the brain) A relay neurone passes the impulse from the spinal cord to a motor neurone (not from the brain) The motor neurone carries the impulse to an effector The effector performs its action The effector's response protects us from danger So the incorrect ones were options two and three. Now you have completed this activity, you hopefully have a better grasp of the jobs of all those complicated neurones and impulses. If you're still rather confused, try re-reading the Introduction and giving these questions another go.
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