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Human Nervous System


Human nervous system for Kids

 

Your nervous system does thousands of different things all at the same time, making itself the most complex system in your body. It is the main system that is specialized for the control and coordination of all body parts. Learn many more about the human nervous system with this interesting lesson, human nervous system for Kids.

 

What is the nervous system made up of?

Each and every part of your body contains nerve cells. Nerve cells are also called neurons. These neurons lie next to one another forming long chains to make the network of nerves. We call this network, along with the brain and the spinal cord, the nervous system.

 

Function of the nervous system:

It transports messages between the body and the brain.

Human Nervous System for KidsThe Human Nervous System

 

 

Your nervous system senses the world around you and sends instructions to every part of your body to keep it working.

 

How does the nervous system transport messages to and from the brain?

Just like the runners of a speedy relay race passing the baton onto the next runner, the nerve cells in your nervous system pass messages to their neighbouring cells to and from the brain.

 

This is easy because of the special structures called synapses. Synapses join nerve cells, called neurons to each other, just like plugs and sockets join up electrical wires. Therefore messages can spread fast to different areas of the body.

 

synapses diagramSynapses in neurones

 

Divisions of the Nervous System

 

  • The Central Nervous System (CNS)
  • The Peripheral Nervous System (PNS)
  • The Autonomic Nervous System (ANS)
  • The Somatic Nervous System

 

The Central Nervous System (CNS)

The central nervous system is made up of the brain and the spinal cord. This is the main control centre of your body.

 

The Peripheral Nervous System (PNS)

The Peripheral Nervous System consists of all the nerves that carry messages to and from the central nervous system to other parts of the body.

 

The Autonomic Nervous System (ANS)

The Autonomic Nervous System has parts in both CNS and PNS. It deals with involuntary actions or autonomic (automatic) body processes, such as breathing, digestion, heartbeat etc.

 

The Somatic Nervous System

The somatic nervous system is the part of the peripheral nervous system, which controls voluntary movements of body.

 

division of nervous systemDivision of Human Nervous System

 

Parts of the Nervous System

 

What are the parts of the nervous system?

The nervous system consists of the following parts.

 

  • The brain
  • The spinal cord
  • Nerves

 

Human Nervous System for KidsHuman Nervous System

 

The Brain

 

The brain is a grayish-pink organ, which is located inside the head, protected by the skull. It is the main control unit of the nervous system.

 

Human BrainHuman Brain

 

Click here to read more about the human brain.

 

Functions of the brain:

The brain’s job is to sort out the signals that it receives, and then send them out. This is how your brain does it;

 

Step 1: Collects signals sent to it

 

Step 2: Makes sense of the information that the signals contain

 

Step 3: Decides what to do

 

Step 4: Sends signals to the muscles to make them take the necessary action

 

The Spinal Cord

 

What is the spinal cord?

The column of nerve tissue that runs down the base of the brain to just below the waist is your spinal cord

 

What is spinal cord made of?

The spinal cord is made up of bundles of nerves that connect the brain to other parts of the body. It runs down from the brain through a canal in the centre of the doughnut-shaped bones of the spine (backbone). These bones which surround and protect the spinal cord are called vertebrae.

 

the spinal cordThe Spinal Cord

 

Function of the brain and the spinal cord:

Your brain and your spinal cord together act as the control centre of your body and make up the central nervous system.

 

Nerves

 

Nerves are made up of bundles of neurons (also called nerve cells). These neurons lie next to one another and link up to form the network of nerves, that carry messages to and from the central nervous system to other parts of the body.

 

Human Nervous System for KidsThe Human Nervous System

 

What are neurons (nerve cells)?

Your neurons or nerve cells are very thin. Also, they can be very long, in fact some of your nerve cells stretch all the way from your big toe to your spine.

 

Function of neurons:

Neurons carry electrical signals back and forth between the brain and the rest of the body.

 

There are three main types of neurons.

 

  • Sensory neurons
  • Motor neurons
  • Relay neurons

 

Sensory Neurons

 

What are sensory neurons?

The nerve cells or neurons that carry signals toward the brain from the eyes, ears, nose, tongue and skin, are called sensory neurons.

 

Motor Neurons

 

What are motor neurons?

The nerve cells or neurons that carry signals away from the brain to the muscles, are called motor neurons.

 

Relay Neurons

 

What are relay neurons?

The neurons, which are found in the brain and spinal cord and allow sensory and motor neurons to communicate are called relay neurons. Relay neurons are located between sensory input and motor output response.

 

A neuron can be either a sensory neuron or a motor neuron, but not both. This means it either carries a signal toward the brain or away from it.

 

structure of a neuronStructure of a neuron

 

What is a synapse?

The place where the end of a neuron (or a nerve cell) connects with another neuron is called a synapse. This is the place where two neurons meet.

 

Neurons do not actually touch each other at synapses. A synapse just allows a coordinated response to a stimulus.

 

synapses diagramSynapses in neurones

 

The Nervous System at work

 

Your nervous system works very quickly. So, you can react fast to internal or external stimuli around you.

 

What is a stimulus (plural: stimuli)?

A stimulus is any change in your environment that causes you to react.

 

Action:

When you feel cold you move into the sun or wear a jacket.

Stimulus:

Temperature drop in the environment

Response:

Moving into the sun or wearing a jacket

 

Did you know?

Signals of your body travel down a nerve at a speed of 350  kilometres per hour. This is faster than a sports car can drive.

 

What are receptors?

There are specialised groups of cells in each of your sense organ, which are the ear, eye, nose, tongue and the skin. These specialised groups of cells can detect changes or stimuli in the environment. Each organ has receptors sensitive to particular kinds of stimulus.

 

Location of the receptors

Receptors sensitive to

Eyes

sense-organs-eyes

Light

senses-eyes-sight

Ears

sense-organs-ear

Sound

senses-ear-hear

Nose

sense-organs-nose

Odour (Chemicals in the air)

senses-nose-smell

Tongue

sense-organs-tongue

Taste (Flavours / Chemicals in your food)

senses-tongue-taste

Skin

sense-organs-skin

Temperature, touch, pressure, pain etc.

senses-skin-touch

 

Types of responses in the body

 

There are two main types of responses performed by your body.

 

  • Voluntary actions (also called ‘thinking actions’)
  • Involuntary actions (also called, ‘reflexes’ or ‘reflex actions’)

 

Voluntary Actions (Thinking Actions)

 

What are voluntary actions?

A voluntary action is any action that you choose to do with your involvement through thinking. You cannot do these actions automatically without thinking. You have to think and volunteer to carry out these actions. This is why they are called voluntary actions or thinking actions.

 

Examples of voluntary actions

 

Walking, talking, reading, writing, drawing, driving, cooking, swimming, kicking a ball, scratching an itch and many more things you do in your daily life fall under voluntary actions.

 

How does a voluntary action take place?

 

Example:

 

Choosing your favourite ice-cream

 

Look at the steps of a voluntary action, if you want to choose your favourite ice-cream;

 

Step 1: Signals from eye to brain
 
Step 2: You see there are different flavours of ice-cream on the table
 
Step 3: Brain decides
 
Step 4: You are looking for your favourite flavour, and you see it
 
Step 5: Signals from brain to muscles in arm and hand
 
Step 6: You pick up your favourite ice-cream
 

ice-cream-image

 

 

Walking

When you need to walk, your brain tells your leg muscles to move, resulting walking.

 

Hunger

When you are hungry, your stomach telling your brain that it’s empty and you must eat.

 

Itching

When you get an irritating itchy feeling, your body reacts by making you scratch.

 

Needing to urinate

When you need to urinate, your body responses to the message that your bladder is full.

 

Riding a bicycle

If you want to ride a bicycle, your brain send signals all along the nerves to the muscles of the legs, telling the muscles how to move your legs to padel or move the bicycle forward, or to stop.

 

Surfing

A surfer’s brain interprets messages from sensory neurons and sends messages via motor neurons to move muscles to balance the body.

 

Similarly, the brain is also receiving signals from the senses and the rest of the body, telling it what is going on in the world around it, so that you can take an umbrella with you if it’s raining.

 

Your nervous system senses the world around you and sends instructions to every part of your body to keep it working.

raining image

 

 

Complex voluntary actions

 

What are complex voluntary actions?

It took you quite a while to learn to ride a bicycle when you were small, but you do not need to think in order to carry out the action ‘riding a bicycle’ now. Moving your leg muscles to pedal the bicycle and move it forward, and also adjusting the other leg to do so, are all automatic now as you got used to them. Walking, tying a shoelace are also similar activities that take a lot of concentration to begin with. After enough practice you make the right movements automatically to perform such activities. These types of voluntary actions are called complex voluntary actions.

 

Involuntary Actions

 

Now we know what voluntary or thinking actions are, and how your brain is involved in a voluntary action.

 

But did you know, that there are some essential actions take place in your body without you thinking?

 

These are autonomic or automatic body processes and we call them involuntary actions.

 

What are involuntary actions?

The actions take place in your body without you thinking about them or choosing to do them are called involuntary actions.

 

The autonomic nervous system (ANS) helps to carry out these actions.

 

Examples of involuntary actions

 

  • Breathing
  • Yawning
  • Blinking
  • Digesting food
  • Keeping your body at the right temperature
  • Controlling heartbeat
  • Blood circulation (Pumping blood around your body)
  • Staying balanced

 

Do you have to think to do these actions everyday? No, not at all. They happen automatically, without you thinking about them. But, these are also the regulatory functions of the brain, because it helps your body to regulate (automatically controls and maintain) itself.

 

Breathing

Breathing carries on even when you are asleep, without you thinking. This shows how automatic breathing is.

 

Yawning

Yawning is an involuntary action. Once you have started to yawn, it is almost impossible to stop it.

 

yawning-image

 

Blinking

Blinking happens without you needing to think about it.

 

Why do you breathe more quickly and your heart beats more rapidly after a strenuous exercise session?

After you exercise strenuously, your working muscles need more oxygen supply. Your brain makes you breathe more quickly and your heart beats more rapidly to increase the amount of oxygen supplied to your working muscles.

 

Why do people turn pale with fright?

When you are frightened by something, the blood vessels in the surface of your skin automatically constrict (become smaller) so that less blood flows to your skin. This is an involuntary action that takes place when you are frightened to protect you. More blood is needed internally to help fuel your muscles for action in response to the situation. This is why you feel your heartbeat and the blood is pumping in your body when you get frightened.

Why do people turn pale with fright
 

 

Reflexes

 

What are reflexes?

If you hand touches a hot pot, you will pull your hand away immediately, even before having no chance to think about it. This is also a type of involuntary action, which is called a reflex action.

 

Coughing and sneezing are some other examples for reflex actions as they automatically take place when harmful substances get into the nose and lungs.

 

sneezingSneezing

 

Click here to read and learn more about reflexes or reflex actions.

 

Do you remember the time that you got tingling feeling in your legs after sitting cross-legged for a long time?

This is because, sitting cross-legged for a long time squashes the nerves in your legs. When you stand up, the nerves start to work again, producing a tingling feeling.

 

cross-legged-imageSitting cross-legged

 

What do the painkillers do?

Before you get a filling at the dental, the dentist gives you an anaesthetic. This is a painkiller that stops nerves passing on pain messages for a short time.

 

Rest for the brain

A good night’s sleep makes your body and  brain slow down. But they don’t stop working. You need to sleep, so that the brain can sort out the events of the previous day.