The brain is one of the most complex organs in the human body. It is protected by the skull.

The brain and spinal cord

The brain manages how we think, feel, learn and move. It also controls other important things in the body, such as breathing and heart rate.

The spinal cord is a long bundle of nerves down the middle of the spine (backbone). It starts at the base of the brain and goes down to the small of the back. Messages between the brain and other parts of the body travel through the spinal cord. The spine is made of bones called vertebrae. They protect the spinal cord.

Illustration of the spinal cord and central nervous system

This illustration shows where the brain and nerves are throughout the body. It shows a person standing with their back to us. A thick line (the spinal cord) runs from the brain in the head down the centre of the back to the small of the back. Thinner lines (peripheral nerves) run from the spinal cord out to all areas of the body.

The brain and the spinal cord together are called the central nervous system (CNS).

The brain and spinal cord are also covered and protected by three layers of tissue (membranes). These are called the meninges. The three layers are:

  • the dura mater
  • the arachnoid
  • the pia mater (see diagram below).

The area between two of these layers is called the subarachnoid space. This space contains a liquid called cerebrospinal fluid (CSF).

CSF also fills spaces inside the brain called ventricles. CSF makes a protective cushion for the brain. It also takes nutrients to the brain and removes waste products.

Nerve cells (neurons)

The brain and spinal cord are made up of billions of nerve cells called neurons. They form a network to communicate with each other. They use this to send chemical messages between the brain and other parts of the body.

Nerve cells are held in place and supported by glial cells. There are different types of glial cells including astrocytes, oligodendrocytes and ependymal cells.

Parts of the brain

The main parts of the brain are the cerebrum, cerebellum, brain stem, cranial nerves and pituitary gland.

Illustration of a side view of the brain

This diagram shows a side view, cross-section of the head, neck and brain. The inner layer of the head is the skull, labelled as bone. Inside the layer of bone, there is a layer surrounding the head. This contains the meninges and subarachnoid space. Within this layer is the cerebrum, or brain. This covers most of the inner area of the head. It has dark wavy lines on it showing the structure of the brain. The brain stem starts in the centre of the brain. It runs down the centre of the neck into the spinal cord and slightly narrows as it leaves the brain stem. At the bottom right of the brain stem is the cerebellum, which is a large circular structure. Either side of the top of the brain stem are small circles. These are the pineal and pituitary glands. The pineal gland, is on the right and the pituitary gland is on the left.

Cerebrum

This is the largest part of the brain and is made up of two halves, called hemispheres. It controls thinking, memory, behaviour and personality. The right half of the cerebrum controls the left side of the body. The left half of the cerebrum controls the right side of the body.

Each half of the cerebrum is divided into four areas, called lobes:

  • The frontal lobe

    This is responsible for thinking, planning, problem solving and behaviour. Certain areas of the frontal lobe control movement in the arms and legs and how we produce speech.

  • The parietal lobe

    This lobe helps us form words. It also helps us interpret touch and other sensations, and makes us aware of our body position.

  • The temporal lobe

    The temporal lobe manages memory, feelings and understanding. It processes what we hear and smell. It also helps us with organising information, learning and speech.

  • The occipital lobe

    The occipital lobe processes information about what we see, for example colour, shape and distance.

Illustration of a side view of the cerebrum

The diagram shows the different lobes of the brain. The frontal lobe is towards the front of the brain and is involved in thought, memory and behaviour. The parietal lobe is behind the frontal lobe. This is involved in language and touch. The temporal lobe is shown below the frontal and parietal lobes. It is involved with hearing, learning and emotions. The occipital lobe is at the back of the brain and is involved in vision. The diagram shows the cerebellum which is under the main part of the brain. It is involved in balance and coordination. The brain stem is shown coming from under the centre of the brain. This deals with breathing, heart rate and temperature.

Cerebellum

This is the area below the cerebrum, at the back of the brain (See diagram above: Side view of the brain). It controls balance and co-ordination.

Brain stem

The brain stem is at the bottom of the brain (See diagram above: Side view of the brain), connected to the spinal cord. It controls important body functions that keep us alive, such as:

  • breathing
  • heart rate
  • blood pressure
  • body temperature
  • eye movements
  • swallowing.

Cranial nerves

These are nerves that go from the brain and brain stem to the eyes, nose, ears, tongue, face and shoulders. They carry messages from these areas about sensations such as taste, smell, sight and hearing. They also carry messages to muscles that control eye and face movements, speech and swallowing.

Pituitary gland

The pituitary gland is a small, oval-shaped gland behind the nose at the base of the brain. It is below the optic nerves that lead to and from the eyes.

The pituitary gland makes hormones. Hormones are chemical messengers that help control growth and how the body works.

Hormones produced by the pituitary gland control other hormone-producing glands in the body.

Pineal gland

The pineal gland is near the centre of the brain, between the two halves of the cerebrum. It makes a hormone called melatonin that helps control sleep patterns.

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