About the brain
The human brain is the most complex known structure in the universe.
It is a single organ that acts as the hub of the central nervous system and as a control centre for all our bodily functions.
What is the brain made of?
How does the brain work?
Different areas of the brain
The illustration below shows the inner and outer
views of the left half of the brain. Click on an area below
to view descriptive text.
What is the brain made of?
The brain is a spongy mass of fatty tissue about the size of a small head of cauliflower and with the texture of blancmange.
It weighs around three pounds (just under 1.5kg) and contains as many as a 100 billion nerve cells. Many of the brain's nerve fibres are wrapped in a fatty insulating sheath called myelin.
The brain is held together by a number of layers of membrane and protected by the skull, or cranium – a hard bone shell. Between the layers of membrane are blood vessels that supply blood to and from the brain.
How does the brain work?
The brain is made up of around 100 billion nerve cells or neurons, each of which is connected to around 10,000 other supporting cells, making around 1,000 trillion connections in total.
This complex network of neurons transmits information through electrochemical signals and electrical impulses travel quickly around the brain and on to the body through the nervous system.
Different areas of the brain
Different areas of the brain control different activities. There are three main parts of the brain: the cerebrum; the cerebellum; and the brainstem.
However, while different parts of the brain appear to underpin particular functions (eg language, memory, vision), it is important to stress that the brain acts as a whole.
For any activity or function, several different (and often distant) parts of the brain will be acting together in a co-ordinated way.
This explains why damage to one part of the brain can have an effect on functions primarily associated with other parts of the brain.
The cerebrum
This is the largest part of the brain and is shaped like a large walnut. It is divided into two halves, known as the left and right cerebral hemispheres.
The brain cells are known as the ‘grey matter’ and the connecting fibres are known as ‘white matter’.
The actual cells are found on the surface of the brain and in ‘nuclei’ or clusters beneath this. However a large proportion of the brain consists of white matter or connecting fibres.
Scientists believe the left hemisphere plays an important part in language, verbal memory, reading, writing, and arithmetic, while the right hemisphere interprets vision, touch, non-verbal memory, music, and emotions.
What is certain is that the right side of the brain controls the left side of the body and vice versa, so damage to the right side of the brain might affect movement in the left side of the body.
Each hemisphere can be divided into four lobes - frontal, temporal, parietal and occipital.
The frontal lobes are located behind the forehead and control activities such as thinking, planning and problem solving and determine emotions and personality.
The parietal lobes, found towards the back of the brain, affect perception of the world and mathematical and spelling sense.
The temporal lobes, situated behind the ears, affect memory, language, understanding and emotion.
The occipital lobes, at the very back of the brain, affect vision and understanding of written words.
The cerebellum
This is a curved lump of tissue at the back of the brain that, amongst other functions, coordinates balance, limb movements and fine motor coordination.
The brainstem
This lower part of the brain – which connects it to the spinal cord – contains the nerve fibres that carry messages to and from the rest of the body via the nervous system.
It also controls all the functions that the body needs to stay alive, such as breathing, heartbeat, blood pressure, digestion and urination, as well as sleep patterns.
Other parts of the brain
Hypothalamus and pituitary gland
This very small area of the brain, located in the centre of the brain, acts as the brain’s inner thermostat controlling the body temperature, but also controlling appetite, sexual arousal and emotions.
It sends chemical signals in the form of hormones to the pituitary gland which sends signals on to different parts of the body.
The limbic system
This comprises several parts (including the hippocampus) and is responsible for the control of emotional behaviour and for storing long-term memories.
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