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The brain

The brain controls the body by sending electrical messages along nerve fibres. The fibres run out of the brain and join together to make the spinal cord, which also takes messages from the body to the brain. Together, the brain and spinal cord form the central nervous system. The brain is made of billions of nerve cells called neurones. It also contains supporting cells called glial cells. It is surrounded by 3 thin covering sheets called the meninges. The brain and spinal cord are bathed in a fluid called cerebrospinal fluid.

The largest part of the brain is called the cerebrum (forebrain). It is divided into left and right sides called cerebral hemispheres. These are divided into areas called lobes, which relate to different functions and systems of the body.

Where the brain joins the spinal cord is an area called the brain stem, which controls automatic body functions. Autonomic functions are those that happen without us thinking about them, such as our heartbeat and breathing.

In the back part of the brain is an area called the cerebellum, which controls balance and coordination. 

In the middle of the brain is the pituitary gland, which is small but very important. It makes hormones that control many different body functions. There is also the pineal gland that makes the hormone melatonin which influences sexual development and controls our sleeping and waking cycles.

Brain tumours cause different symptoms depending on their position in the brain. In adults, many brain tumours are ones that have spread from an original cancer elsewhere in the body. These are called secondary tumours.


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How the brain works

The brain is the control centre of the body and mind. Everything we do, think or feel involves the brain. It controls the body by sending electrical messages along nerve fibres. The nerve fibres run out of the base of the brain and into the spinal cord. This cord of nerve fibres runs down the middle of the spinal bones. From the spinal cord the nerve fibres spread out to all areas of the body. The spinal cord also communicates messages and sensations from nerves in the body to the brain. 

Together, the brain and spinal cord form the central nervous system. A clear fluid circulates around the brain and spinal cord and protects them. It is called cerebrospinal fluid or CSF for short. 

The brain is made of nerve cells called neurones. There are billions of these neurones. Also in the brain are other types of cells that support the neurones. These are called glial cells. There are many different types of cells in the brain and these can develop into different types of brain tumours

Different areas of the brain control different parts of the body as well as our thoughts, memories and feelings.

Brain tumours can develop anywhere in the brain. They can develop from

  • The cells that make up the brain tissue
  • The nerves entering or leaving the brain
  • The coverings of the brain (the meninges)

Tumours cause different symptoms depending on the part of the brain they are growing in. So, to understand why brain tumours cause particular symptoms, it helps to know a little about the different areas of the brain.


The parts of the brain

The main areas of the brain include

  • The cerebrum (forebrain)
  • The brain stem
  • The cerebellum (hindbrain)

You can see these in the diagram below.

Diagram showing some of the main areas of the brain

The brain is surrounded by 3 protective membranes called the meninges. The pituitary gland and pineal glands are within the brain tissue but they are part of the hormone system.


The cerebrum

The cerebrum is the largest part of the brain. It is also called the forebrain and is divided into 2 halves – the right and left cerebral hemispheres. They control movement, thinking, memory, emotions, senses and speech.

As the nerve fibres leave the brain, they cross over from one side to the other. This means that the nerves that come from the right side of your brain control the left side of your body. So if you have a brain tumour causing weakness on the left side of your body, the tumour will be in the right side of your brain. 

Each cerebral hemisphere is divided into 4 areas which are explained below

Diagram showing the lobes of the brain

The frontal lobe contains areas that work with speaking, planning, problem solving, starting particular movements, and some aspects of personality and character. Towards the back of the frontal lobe are areas that coordinate movement and also process sensations. 

The temporal lobe is where we process sounds and also where memories are stored. A tumour here can cause strange feelings of having been somewhere or done something before (also called déjà vu). It may also cause odd tastes or smells.

The parietal lobe is where touch, temperature, pressure and pain sensations are received and processed. It is where we recognise objects in the world around us and store that knowledge. One area also processes the information when people speak to us. A tumour here can affect speech, reading, writing or the understanding of words. 

The occipital lobe is the visual centre of the brain and processes what we see, including colour, shape and distance. A brain tumour in this area can cause sight problems.


The brain stem

The brain stem controls body functions that we usually don't think about. Blood pressure, swallowing, breathing and heartbeat are all managed by this area of the brain. The 2 main parts of the brain stem are called the pons and the medulla oblongata. The brain stem also includes a small area above the pons called the midbrain.

Diagram showing the brain stem which includes the medullaa oblongata, the pons and the midbrain

The brain stem is also the part of the brain that connects the cerebral hemispheres and the cerebellum with the spinal cord. All the nerve fibres leaving the brain pass through here to go to the limbs and trunk of the body.


The cerebellum

The cerebellum is also called the hindbrain. It is the purple area in the diagram.

Diagram showing the parts of the brain

The cerebellum controls balance and posture. It is also involved with the timing and coordination of skilled movements. Tumours here can cause loss of balance or difficulty coordinating your movements. Even something that we usually think is simple, such as walking, needs a lot of coordination. We have to get our arms and legs doing the right thing at the right time. Normally, we don't even think about this because the cerebellum does it automatically.


The pituitary gland and pineal gland

The pituitary gland is a small gland right in the middle of the brain. It is marked in yellow in the diagram above. The pituitary gland makes a lot of different hormones. And it controls many different body functions. Pituitary hormones control

  • Growth
  • The speed of body processes (your metabolism)
  • The production of natural steroids in the body
  • Periods and egg production in women
  • Sperm production in men
  • Breast milk production after the birth of a baby

The pineal gland is a very small gland deep in the brain. It makes the hormone melatonin, which controls sleep patterns.

Diagram showing the pineal and pituitary gland


The ventricles

Ventricles are spaces inside the brain, filled with the fluid called cerebrospinal fluid or CSF. The ventricles connect with the space in the centre of the spinal cord and with the membranes covering the brain (the meninges). So the fluid can circulate around and through the brain and around the spinal cord.

Diagram showing where the ventricles are in the brain

The fluid is mainly water with a little protein, sugar (glucose), some white blood cells and some hormones. A growing brain tumour can block the circulation of the fluid. The resulting increased pressure inside the skull from fluid build up is called hydrocephalus and can cause symptoms. With some types of brain tumours cancer cells can spread in the CSF, causing symptoms similar to meningitis – headaches, sickness, and problems with sight and movement.


The meninges

The skull protects the brain. Inside the skull, and covering the brain, are 3 thin sheets of body tissue. These are called the meninges and they also help to protect the brain.


Effects of brain tumours

The symptoms that a brain tumour may cause depend on its position in the brain.  

In adults, many tumours found in the brain are cancers that have spread to the brain from other parts of the body. These are called secondary brain tumours. There is information about secondary brain tumours in this section of the website.

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Updated: 22 September 2015