The brain - structure and function
The brain, together with the spinal cord, makes up the central nervous system (CNS). This is the 'control centre' that coordinates the body’s functions.
The brain is contained within the skull, which protects it. Between the brain and the skull there are three layers of membrane called the meninges. These completely cover the brain and spinal cord (see diagram opposite) and help to protect it. Between two of these layers is a space called the subarachnoid space. This space contains a fluid called cerebrospinal fluid (CSF).
Main structures and functions of the brain
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The main parts of the brain are:
the cerebrum (the forebrain)
the cerebellum (the hindbrain)
the brain stem.
Cerebrum (large yellow area in diagram below)
This is the largest area of the brain and controls all higher mental functions, such as thinking and memory. It’s made up of two halves, or hemispheres. The right cerebral hemisphere controls the left side of the body, and the left cerebral hemisphere controls the right side of the body.
Each cerebral hemisphere is divided into four areas, known as lobes:
Frontal lobe (red area in the diagram below)
This controls thought, memory, planning, problem solving and behaviour.
Parietal lobe (blue area)
This is responsible for language, helping us form words and thoughts. It also deals with touch and how we recognise sensations, and helps us be aware of our body position.
Temporal lobe (yellow area)
This helps us understand and process what we hear. It’s also involved with how we learn and organise information.The temporal lobe is also responsible for emotions and emotional memory.
Occipital lobe (green area)
This is where all visual information is processed, such as colour, shape and distance.
Cerebellum (orange area)
This is the back part of the brain and is concerned with balance and coordination. These activities are carried out automatically (subconsciously) by this area of the brain and are not under a person’s control.
Brain stem (purple area)
This controls the basic functions that are essential for maintaining life, including breathing, body temperature, heart rate and blood pressure. It also controls eye movements and swallowing. It’s a very sensitive and important part of the brain, and it connects the cerebral hemispheres to the spinal cord.
Just below the base of the brain is the pituitary gland (see diagram above). This is a small gland that makes lots of different hormones that control and regulate the other hormone-producing glands of the body.
Like every other organ in the body, the brain is made up of cells. There are about 40 billion nerve cells, called neurones, within the brain. Everyone is born with a similar amount.
Unlike other cells, nerve cells can’t replace themselves. In fact, as we get older there is a gradual decrease in their number.
Nerve cells communicate with each other, and other parts of the body, by sending messages (nerve impulses) through a system of nerve pathways or networks.
Nerve cells are held in place and supported by cells called glial cells. There are different types of glial cells, including astrocytes, oligodendrocytes and ependymal cells.