The human body: Week three
This article has been specially written for thousands of pupils from across Northern Ireland who are doing the Belfast Telegraph cross-curricular project themed on the human body. Over a six week period we will look at systems in the human body. This week we will focus on the nervous system - one of the most important systems in the body.
The nervous system
Every thought and movement that we make is controlled by the brain.
The brain is more complex than any computer ever invented.
It enables us to think, speak, hear, see, feel and move. It works nonstop, day and night.
The human nervous system consists of:
- the central nervous system (CNS) – the brain and spinal cord
- the peripheral nervous system – nerve cells that carry information to or from the CNS
The Central Nervous System
The brain consists of billions of living units called neurons or nerve cells.
Neurons carry millions of messages to the brain along the spinal cord, which runs down the back and links the brain to the rest of the body.
When these messages, or nerve signals reach the brain, it sorts
them out and sends instructions to the rest of the body along the nerves.
The Peripheral Nervous System
Nerves are like wires, made of bundles of nerve cells.
Sensory nerves take signals from the eyes, ears and skin to the brain; motor nerves take signals from the brain to the muscles, telling them when to move the body.
Neurones are adapted to carry electrical impulses from one place to another.
- they have a long fibre (axon) which is insulated by a fatty sheath
- they have tiny branches (dendrons) which branch further into dendrites at each end (like the branches of a tree).
A reflex action is a way for the body to automatically and rapidly respond to a stimulus to minimise any further damage to the body.
When you prick your finger, sensory nerves carry signals to the spinal cord.
Here they pass through intermediate nerve cells and then straight back out to the muscles making them pull the finger away.
This is called a reflex, an automatic reaction that we make without thinking.
The function of the brain in the CNS
The largest parts of the brain are the two folded cerebral hemispheres. Our thoughts are based in these hemispheres. The outer layer of the brain is called the grey matter. It is rich in nerve cells.
The inner layer is called the white matter. It consists mainly of nerve fibres.
If the two hemispheres were spread out, they would cover an area the size of a pillowcase.
If you were to split the brain down the middle into two symmetrical, or equal parts, you would have a right and left hemisphere.
Although equal in size, these two sides are not the same, and do not carry out the same functions.
The left side of the brain is responsible for controlling the right side of the body. It also performs tasks that have to do with logic, such as in Science and Mathematics.
On the other hand, the right hemisphere coordinates the left side of the body, and performs tasks that have do with Creativity and The Arts.
Science and math
Name: Nathan Caulfield
How tall are you?
What colour of eyes do you have?
What exercise do you enjoy to keep your body healthy?
Football and Irish dancing.
Which healthy foods do you enjoy eating?
Oranges, bananas and vegetable soup.
What is your top tip for healthy living?
Always eat a healthy breakfast, stay active and get plenty of sleep.