The nervous system

Mind map

Road safety

Many victims of traffic accidents in cities and villages are children. The main reasons are: crossing the street unsafely, riding a bicycle without wearing a helmet, and not wearing a seatbelt in the car.

In some cases, the consequences of these accidents are very serious. The spinal cord and the brain can be damaged. Spinal cord injuries can cause paralysis in different parts of the body, and brain injuries can affect many activities such as thinking, talking, moving, etc.

In order to be safe and avoid these types of accidents, we always need to be careful when we cross the road at pedestrian crossings or traffic lights. In addition, we always need to wear bicycle helmets and seatbelts.

It is estimated that the proper use of a bicycle helmet can reduce the risk of head injury by 70 %.

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Read and understand

What are the causes of most traffic accidents involving children?

What important organs can be damaged in these accidents?

What are the potential consequences of injuries to these organs?

How can wearing a helmet help?

SPEAKING. In small groups, discuss other road safety measures. Do you follow all these measures?

What do you remember?

The senses

Human beings have five senses: sight, hearing, touch, taste and smell. They allow us to experience the world around us.

Name the sense organs.

Give an example of a pleasant and an unpleasant experience using the same sense organ.

If we close our eyes, how can we distinguish a feather from a cactus?

What is sensitivity?

Through sensitivity, we respond to changes in the external environment. These changes are called stimuli.

Look at these examples:

If the Sun is too bright, we respond by shading our eyes.
If we see a large rock falling towards us, we respond by moving away.
If we walk into a room and there is a bad smell, we respond by holding our nose or leaving the room.

How does sensitivity work?

If somebody throws a ball to us, we respond by trying to catch it. In order for this to happen, various organs and systems are involved.

Sense organs capture information from the environment. Sense organs have groups of specialized cells, called receptors, which are sensitive to stimuli.
The nervous system controls the function of sensitivity. First, the nerves carry information from the sense organs to the brain. The brain receives and interprets the information and decides how we should respond. Finally, the nerves carry responses from the brain to the muscles.
The locomotor system is made up of the muscular system and the skeletal system. Muscles receive orders from the brain and work with bones to make the body move.

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Internal coordination

Many processes are occurring inside our body at all times, for example, digestion and blood circulation. These processes are coordinated in order for the body to function properly.

This is called internal coordination, and it is part of the function of sensitivity. The nervous system is responsible for internal coordination.

Diagram of the function of sensitivity

What do you know about sensitivity?

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The sense organs capture information from the environment and send it to the brain through the nerves.

Eyes and sight

The eyes are the sense organs of sight. They detect light so we can see shapes and colours, and estimate distances.

The information captured by receptors in the retina travels to the brain through the optic nerve. The brain receives and interprets this information.

Parts of the eye

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Ears and hearing

The ears are the sense organs of hearing. They detect sounds and their properties, and where these sounds come from.

The information captured by receptors in the cochlea travels to the brain through the auditory nerve. The brain receives and interprets this information.

Parts of the ear

Skin and touch

The skin is the sense organ of touch. It detects temperature, pain, pressure, etc.

The information captured by receptors in the skin travels to the brain through the nerves. The brain receives and interprets this information.

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The tongue and taste

The tongue is the sense organ of taste. It detects different flavours.

The information captured by receptors in the taste buds travels to the brain through the taste nerves. The brain receives and interprets this information.

Touch, taste and smell organs

The nose and smell

The nose is the sense organ of smell. It detects different smells in the air that we breathe.

The information captured by receptors in the olfactory epithelium travels to the brain through the olfactory nerve. The brain receives and interprets this information.

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Sense detective

Awesome senses.

What do you know about the sense organs?

What do you know about senses?

Look at the diagrams of the eye and the ear. Identify the receptors and nerves in each sense organ.

A. Diagram of the eye.

B. Diagram of the ear.

In the eye, the receptors are in the retina, inside the eyeball...

CRITICAL THINKING. Write all the senses that can be used to identify each object. Then, discuss your answers with a partner.

Nervous tissue under a microscope.

The nervous system carries out the function of sensitivity. The nervous system is in charge of three important tasks:

It receives and interprets information from external and internal environments.
It gives the appropriate orders for our body to respond to stimuli.
It controls and coordinates all organs and systems in our body, for example, the ears, the heart and the digestive system.

We can see these three tasks, for example, in a race: you see another runner pass you; you try to run faster; your heart rate increases.

The nervous system is made up of two parts: the central nervous system and the peripheral nervous system. It is formed by only one type of tissue, nervous tissue.

Neurons

Nervous tissue consists of nerve cells or neurons. These are grouped together to form nerves. Neurons have three parts:

The body, which is the widest part of the neuron. The other parts reach out from the body like branches.
Dendrites, which receive messages from the sense organs or other neurons.
The axon, which transmits messages to other neurons.

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Parts of the neuron

The central nervous system

The central nervous system has two parts: the brain and the spinal cord.

The brain is protected by the cranium and has three parts:

The cerebrum controls voluntary actions, like running and talking. It also stores data and memories, processes thoughts and controls emotions.
The cerebellum controls movement, coordination and balance.
The brainstem controls internal organ activities that we do not need to think about, for example, heart rate and breathing.

The spinal cord is a long, thin bundle of nervous tissue, protected by the spinal column. It extends from the base of the brain to the bottom of the spine, and connects the brain and the peripheral nervous system. The spinal cord produces involuntary responses, such as when we move our hand away from very hot objects.

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The peripheral nervous system

The peripheral nervous system consists of nerves that extend throughout the body. It connects the central nervous system to our sense organs, muscles, internal organs, etc.

There are two types of nerves:

Sensory nerves. These receive messages from receptors in the sense organs and send these messages to the central nervous system.
Motor nerves. These send orders from the central nervous system to the other organs.

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What do you know about the brain?

What do you know about the nervous system?

Look at the diagram of a neuron and describe each part.

The body is wide and flat.

The axon and the dendrites reach out from it...

How many axons does a neuron have?

What is the difference between the dendrites and the axon?

Why are injuries to the brain stem especially dangerous?

Choose only the words related to the nervous system and write sentences.

cerebrum
eyes
sensory nerves
brainstem
bones
muscles
spinal cord

Our body is capable of two different types of movement: voluntary movements and reflex movements.

Voluntary movements

We make voluntary movements in response to different stimuli. They are actions that we perform consciously.

We are aware of them and can start and stop them as we wish. Some examples are walking, reading and chewing.
For these movements to happen, the brain needs to send an order. Voluntary movements involve three main steps:

The sense organs capture a stimulus and send information to the cerebrum through sensory nerves.
The cerebrum interprets the information and sends an order to the muscles through motor nerves.
The muscles carry out the order by performing the corresponding movement.

Voluntary movements can be divided into two types:

Gross motor skills are large movements such as walking, sitting or waving your hand.
Fine motor skills are smaller, more precise movements, such as writing or picking up a phone.

Voluntary movements

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Reflex movements

Reflex movements are rapid, automatic responses to stimuli. We perform these involuntary movements without thinking about them. In many cases, they are movements to protect us from being hurt in dangerous situations.

In many reflex movements, the response is produced by the spinal cord, not the brain. This is why the responses are so quick. These movements involve three main steps:

A sense organ captures a stimulus that can be harmful or dangerous, and sends a message to the spinal cord.
The spinal cord receives this message and gives the order to perform a particular movement.
The order reaches the muscles through the motor nerves and the muscles perform the movement.

Voluntary and reflex movements

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Movements

SPEAKING. Look at the picture. Which object could be considered the cerebrum, which one a muscle and which one a nerve? Discuss with a partner.

Describe two examples of each type of movement that you have experienced.

voluntary movements
reflex movements

Wear a bicycle helmet properly

Wearing a bicycle helmet is extremely important to reduce the risk of head injuries.

In order for the helmet to protect your head, it needs to fit properly. Your helmet needs to sit level and in place on your head.

Learn how to wear a helmet

Test yourself

Do you know how to wear a helmet properly?

Have you done it properly?
Write a few lines describing the results.

Wear a bicycle helmet properly. Show that you can do it. Bring a bicycle helmet to class. With a partner, practice how to wear a helmet properly. First, help you partner to fit his/her helmet. Then, try to fit your helmet by yourself.

Have you done it properly? Write a few lines describing the results.

1. Revision

Activities

The eye and the ear

What do you know about receptors?

Where are the sense receptors?

The central nervous system

The nervous system

Final activities

Complete the flow diagram about reflex movements. Then, draw a flow diagram about voluntary movements.

muscles - sense organ - motor nerves - sensory nerves

WRITING. Use the situation in the photograph to explain how the function of sensitivity works. Identify the stimulus, the sense organ and the response.

Classify the words in the table. Add more words.

ossicles - hair - lens - nostril - outer ear - iris - pore - eardrum - taste buds - optic nerve

eyes	ears	skin	tongue	nose

Explain the difference between sensory nerves and motor nerves.

2. Test yourself

Summary

Check your progress

3. Play

What sense are they using?

Show your skills

Write examples of situations in which feeling pain can warn you of danger.

Take a sensory walk using sight, hearing, touch and smell to make observations. Write a description of your sensory walk.
Draw a comic strip illustrating a voluntary movement and another one illustrating a reflex movement.

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Getting started

Mind map

Road safety

Read and understand

The senses

1. The function of sensitivity

What is sensitivity?

How does sensitivity work?

Internal coordination

Diagram of the function of sensitivity

What do you know about sensitivity?

2. Sense organs and senses

Eyes and sight

Parts of the eye

Ears and hearing

Parts of the ear

Skin and touch

The tongue and taste

Touch, taste and smell organs

The nose and smell

Anosmia

Sense detective

What do you know about the sense organs?

What do you know about senses?

3. The nervous system

Neurons

Parts of the neuron

The central nervous system

The peripheral nervous system

What do you know about the brain?

What do you know about the nervous system?

4. Movements

Voluntary movements

Voluntary movements

Reflex movements

Voluntary and reflex movements

Movements

Know how to

Wear a bicycle helmet properly

Learn how to wear a helmet

Test yourself

Do you know how to wear a helmet properly?

Have you done it properly? Write a few lines describing the results.

Show what you know

1. Revision

The eye and the ear

What do you know about receptors?

Where are the sense receptors?

The central nervous system

The nervous system

Final activities

2. Test yourself

Summary

Check your progress

3. Play

What sense are they using?

Show your skills

Have you done it properly?
Write a few lines describing the results.