Nervous System

Biology – Body

systems

Year 9

Learning Intentions

•
Understand that the body has receptors that detect changes (stimuli)
in the environment

•
Investigate the first two of 5 main types of external receptors (light,
sound, taste, smell and touch).

Your body - Receptors

●
Your body responds to changes in its
environment. These changes are
called Stimuli.

●
Quick activity: list 10 ways in which
you think your body reacts to different
changes in the environment.

○
Consider: are we always
conscious of these changes?

●
What makes you aware that you are
hungry or thirsty?

Key words:

●
STIMULUS – any information that
the body receives that causes it to
respond

●
RESPONSE – a structure that
detects a stimulus or change in the
normal functioning of the body.

Responding to change

●
Another example of stimuli are bacteria and viruses that we are exposed to every
day.

○
Our bodies are constantly monitoring the numbers and fighting off harmful
microorganisms without us even knowing!

●
The body can detect five main signals:

○
Light

○
Sound

○
Smell

○
Taste

○
touch

●
The sense organs (eyes, ears, tongue, nose and skin) are highly specialized to
receive stimuli from the environment

Sight

•Sight tells us more about the world than any
other sense

•Pupils change size to control the amount of
light that enters the eye.

•Different types of photoreceptors at the back
of the eye transform light into nerve signals
for the brain

•This means your brain also helps you see;
information sent from the eyes tells your brain
what you are seeing.

Hearing

•Sound vibrations (that we have already learned about) reach your
ears and cause your eardrums to vibrate.

•The vibrations move along the bones in your ear to your cochlea to be
converted into nerve impulses for the brain to interpret.

Task: Eco-location

Echolocation is a process used by certain animals, such as bats and dolphins, to
navigate and hunt by emitting sound waves and interpreting the echoes that bounce
back from objects.

In groups research the following;
•Animals that use echolocation (eg. bats, dolphins etc)

•How echolocation works: sound production, sound waves and echo reception

•The anatomy involved in echolocation (eg. bat larynx)

•The advantages o echolocation in different environments (eg night / murky
water)

•How does echolocation help the animal respond to its external environment?

Discuss / share with the class

Taste

•
Taste buds on your tongue contain special receptor cells that react to
chemicals in foods

•
Sweet

•
Salty

•
Sour

•
Bitter

•
Unami (savoury)

•
When you eat or drink, the information from the taste receptor cells is sent to
your brain through nerves.

•
The mix of chemicals detected by the brain gives flavour.

Smell

•
Smell also uses chemical receptors to detect scent.

•
Receptors in the nostril detect chemicals, and then send messages to the
brain.

•
Smell is very closely linked to taste

•
Which is why when you have a blocked nose, it can be difficult to taste
your food!

Touch

•
While the other four senses have specific locations, touch
can be felt all over the body – because it is felt by the
skin!

•
The inner layer of the skin is called the dermis, and has
many nerve endings that can detect

•
Cold

•
Heat

•
Pressure

•
Pain

•
Information is collected by the different receptors and
sent to the brain for processing and reaction

Questions

1.
Define the term ‘stimulus’

2.
Identify the five major sense organs

3.
Stimuli can be changes in our immediate environment or changes within our
bodies Describe two examples of each

4.
Describe two situations in which each sense organ would need to respond

5.
Compare the way you detect smell and the way you detect taste

6.
Some people claim they have a sixth sense – explain what do you think this
refers to? Do you think this is true?

Stimulus response

Each of these senses have particular types of stimulus that signal processing in the

brain.

This then creates a form of output or response in a person.

For example, a spider crawling on your skin… what stimulus might you identify?

•Touch (mechanical) : feeling light movements on your skin

•Sight (electromagnetic): your eyes see a black, hairy, eight legged shape

This is then processed by the brain as potentially a threat to your health.

What outputs might you experience?

•Body: flicking the spider off, screaming, increased heart rate

•Emotions: feeling scared or anxious about what might happen

Types of stimulus

Our bodies collect information through our 5 sensory organs. The inputs are

classified into three main types;

•Mechanical stimulus: sound waves, touch, pressure and pain

•Chemical stimulus: smells and tastes

•Electromagnetic stimulus: visible light and radiant heat. Some animals are
able to detect other parts of the electromagnetic spectrum, such as UV
light.

TASK: Match each sensory experience with the type of input detected by
the senses.

NERVE CELLS

LEARNING INTENTIONS

•
Neurons are cells in our body that enable messages to be passed quickly

•
A change is detected by the receptor and an electrical message is passed along the
neuron to the synaptic terminal

•
Chemical neurotransmitters pass the message across the gap to the next neuron

•
The myelin sheath protects parts of the neuron and increases the speed of messages
being sent

Nerves

•
The basicunitof the nervous system is the nerve cell, or neuron

•
Neurons have many highly specialized features. Each neuron has a large cell body that
connects to a long thin axon.

•
The axon is responsible for carrying nerve impulses away from the cell body and can be
up to 1m long in some cases!

Nerves

•Nucleus: contains the DNA of the cell

•Cell body: contains all the organelles needed to maintain life

•Axon: carries the electrochemical message along the neuron

•Myelin Sheath: fatty layer that covers the axon and allows the electrochemical impulses
to travel along the axon quickly and effectively

•Synaptic terminal: where electrochemical impulses (neurotransmitters) are packaged and
sent into the synapse.

•Dendrites: where electrochemical impulses (neurotransmitters) are detected / received

Activity - Build your own neuron

Riskassess

Method

NEURONS continued

LEARNING INTENIONS

•Describe the passage of information through a neuron, across the synapse
and to the next cell

•Explain how sensory, motor and interneurons communicate information
around the body.

NEURONS

RECALL: the anatomy of a neuron

•Nucleus: contains the DNA of the cell

•Cell body: contains all the organelles needed to maintain life

•Axon: carries the electrochemical message along the neuron

•Myelin Sheath: fatty layer that covers the axon and allows the electrochemical impulses
to travel along the axon quickly and effectively

•Synaptic terminal: where electrochemical impulses (neurotransmitters) are packaged
and sent into the synapse.

•Dendrites: where electrochemical impulses (neurotransmitters) are detected / received

Types of Neurons

There are three different types of neuron, all with different

jobs

Sensory neurons: sensitive to various stimuli, and collect

information from either the internal or external body
environment.

Interneurons: link sensory and motor neurons as well as

other interneurons. These are the most common type of
neuron.

Motor neurons: carry messages from the central nervous

system to muscle cells throughout the body – leading to a
response.

VENN DIAGRAM – mini task

In your books / notes, create a Venn diagram of 3 circles showing the similarities and

differences (structurally and functionally between sensory, motor and interneurons.

INTERNEURON

MOTOR NEURON

SENSORY NEURON

Sending a Message

Nerves work like electrical wires – they carry electrochemical

impulses along the dendrites, through the axon and into the
axon terminals where the neurotransmitters are stimulated to
be packaged and exit the end of the terminal and into the
synapse (gap between axon terminal and receiving cell)

This then triggers an electrochemical response in the next cell

and the circuit continues.

KEY TERMS

Synapse: a small gap between two neurons that must be crossed by

neurotransmitters

Neurotransmitter: a chemical messenger that crosses the synapse between the

axon of one neuron and the dendrite of another neuron

Sensoryneuron: a nerve cell that carries a message from a receptor to the central

nervous system

Interneuron: a nerve cell that links sensory and motor neurons
Motor neuron: a nerve cell that carries a message from the central nervous system

to a muscle cell.

MAKE SURE THESE ARE IN YOUR NOTES

QUESTIONS

1.

Describe the features of a neuron that enable it to pass messages on to other neurons

2.

Describe where you will find sensory neurons that detect: smell, taste, sound, touch and light

3.

Describe the role of the myelin sheath

4.

With a partner, create ways to remember the difference between sensory, motor and interneurons

5.

Investigate one or more of the following nerve diseases and answer the following questions

•

Motor neuron disease

•

Multiple sclerosis

•

Kennedys disease

•

Lou Gehrigs disease

1.

What causes these diseases?

2.

What happens to the neurons in this disease?

3.

Can it be cured / reversed?

4.

What are the symptoms?

NERVOUS SYSTEM

LEARNING INTENTIONS

•
Students will be able to describe the stimulus response model

•
Students will be able to explain how reflex actions can provide

responses that saves lives.

●
Stimuli are detected by receptors and the message is sent to
the spinal cord and brain via the sensory neurons.

●
The brain and spine form what is called the Central Nervous
System, and is full of interneurons that pass around
information until the brain decides what to do with it.

●
Once a decision is made, Motor neurons are responsible for
passing the message onto the muscles. Muscles are called
effectors because they are the cells that carry out the
response.

STIMULUS RESPONSE MODEL

●
What happens when you accidentally touch something hot?

●
A reflex, or reflex action, is an involuntary (without thinking) and nearly
instantaneous movement in response to a stimuli.

●
During a reflex action, the sensory neuron carries the message from the receptor to
the spinal cord.

●
The interneuron then sends two messages at the same time: one to the brain and
one to the muscles via the motor neuron.

●
This means the muscle moves at the same time as the brain getting the message.

REFLEXES

●
This makes reflexes even faster than normal responses. Most reflexes help in
survival situations – can you think of any others?

REFLEXES

●
Define the following terms

○
Receptor

○
Effector

○
response

●
Describe the stimulus response model

●
Explain why the brain is not involved in a reflex action

●
Explain the advantage of a baby having a startle reflex

●
If a person has damaged their upper spinal cord, they may not be able to feel their toes.
Analyse whether this will affect their knee jerk reflex

QUESTIONS

●
Ruler drop activity

Students pick one of the four options below for comparing reaction distance. Your choice will
guide you for determining your independent variable.

1.

Dominant hand compared to non-dominant hand

2.

Sitting compared to standing

3.

Watching the ruler compared to not watching the ruler

4.

Distracted (listening to music, or having someone talk to you etc.) compared to non-
distracted

REFLEX Activity – Ruler drop

LEARNING INTENIONS

●
Describe the roles of the central nervous system, peripheral, somatic and autonomic
nervous systems.

●
List the lobes of the brain and describe their main functions

CENTRAL NERVOUS SYSTEM

Central nervous system (CNS)

●
The central nervous system is the control centre of the
body.

●
The two main parts of the CNS are the brain and spinal
cord

●
The brain is the processing centre of the body and is
mainly concerned with survival

●
Interneurons in the brain gather information about what is
happening inside and outside the body, compares to
previous experiences and then makes a decision on how
to respond.

Lobes of the Brain

●
The cerebrum (outside of the brain) is divided into four lobes or sections. Each one with
a different function.

●
Frontal lobe: regulates emotions, reasoning, movement and problem solving

●
Parietal lobe: manages perception of senses of touch, taste, pain and temperature.

●
Temporal lobe: region near ears that recognizes sounds and smells.

●
Occipital lobe: back of the brain receives information from eyes.

JIGSAW activity

Lobes of the brain:

1.

Split class into 4 groups

2.

Each group is to research & create a Canva information
poster about one of the 4 lobes of the brain.

3.

Information to be included = location of the lobe, what
sections of personality / human actions is it
responsible for, how it receives information, a diagram
of the lobe, what happens when / if this lobe is
damaged, any other information you would like to
include.

4.

Share back with the class

Peripheral nervous system (PNS)

●
The peripheral nervous system is a large system made up of all the nerves outside
the CNS.

●
PNS carries information to and from the CNS to the rest of the body such as limbs
and organs

●
There are two parts to the PNS

○
Somatic nervous system: controls voluntary skeletal movements such as
waving or reaching out to take an object

○
Autonomic nervous system: controls involuntary movements (without
conscious control) including heartbeat, digestion, respiration, perspiration and
salivation. Is responsible for maintaining homeostasis.

QUESTIONS

1.

Identify the two parts of the body that make up the Central Nervous System

2.

Describe the role or function of the peripheral nervous system

3.

Describe how the PNS and the CNS work together. Use an example to illustrate your
answer

4.

Explain why if you slipped and hit the back of your head, everything might go black

5.

Create a scientific diagram of the brain that shows the four lobes. In each of the lobes:

1.

Write the functions that are carried out in that lobe

2.

Draw something to remind you of the functions carried out in that lobe.

WHEN THINGS GO WRONG

•Provide examples of diseases and problems affecting the nervous system

•Explain the relationship between the myelin sheath and multiple sclerosis.

LEARNING INTENTIONS

When things go wrong: Nervous
system

•
The nervous system plays a very important role in
coordinating and regulating the body.

•
Things such as the spinal cord being damaged
(paraplegia), having a slipped disc pressing on the
nerves in the spinal cord or the myelin sheath in
neurons being damaged, all effect a persons ability to
perform everyday functions.

Slipped disc

•
Your backbone consists of 26 bones or vertebrae that surround the nerves in
your spinal cord.

•
Between each vertebra is a sac called a disc, which is filled with thick fluid and
allows the vertebrae to move

•
If a disc becomes weak and puts pressure on the nerves, this will cause pain /
numbness along the nerve.

•
Treatment includes pain relief, or occasionally, surgery.

Multiple sclerosis

•
The myelin sheath plays a very important role in
ensuring the electrical message passes along
the axon of a neuron.

•
If the myelin sheath is damaged, the signal can
be lost and muscles become weak.

•
The sufferer can feel dizzy. Tired, or have
difficulty seeing properly.

•
This is an incurable disease.

Motor Neuron Disease

•
Also known as ALS

•
Neurons that send messages to the muscles become
weak and eventually lose function.

•
As the muscles weaken they cramp and become stiff
– starting in the legs and arms and progressing to the
face and chest. This effects the persons ability to talk
and eventually breathe.

•
Scientists do not know what causes the motor
neurons to lose their function.

Alzheimer’s disease

•
Alzheimers disease is caused by progressive damage to the neurons in the brain.

•
This results in problems with short term memory.

•
Sufferers can forget how to get home or where they are.

•
The cause of Alzheimer’s disease is not known, but it is suggested that
potentially due to plaque build up around the neurons, blocking nerve cells from
transmitting signals.

QUESTIONS

1.
What is the name of the individual bones that make up the spine?

2.
Describe the role of a disc in the spinal column

3.
Explain why the destruction of the myelin sheath causes symptoms in multiple
sclerosis

4.
Identify another name for motor neuron disease. Describe the role motor
neurons usually play in a healthy nervous system

5.
Think about where you were and what you were doing an hour ago. Describe how
you would be affected if you could not remember this.

6.
Contrast quadriplegia and paraplegia.