Central nervous system (CNS)

The central nervous system (CNS) is made up of the brain and spinal cord.

It is part of the nervous system. The other part is the peripheral nervous system, which is made up of nerves that connect the brain and spinal cord to the rest of the body.

The central nervous system is the body's processing centre.

The brain controls most of the functions of the body, including:

• awareness
• movement
• thinking
• speech
• the 5 senses — seeing, hearing, feeling, tasting and smelling

The spinal cord is an extension of the brain. It carries messages between the brain and the rest of the body via a network of peripheral nerves.

The nervous system is made up of basic units called neurons. Neurons are also known as brain cells. Neurons are arranged in networks that carry electrical and chemical messages to and from the brain, to the rest of the body.

The brain is made up of grey matter and white matter:

• Grey matter consists of nerve cell bodies and blood vessels.
• White matter consists of axons, which are long cords that extend from the nerve cells. They are coated in myelin, a fatty substance that insulates the axons to help electrical messages travel faster down the axons.

The brain and spinal cord are protected from damage by:

• cerebrospinal fluid (CSF) — a clear liquid that surrounds them
• the meninges — 3 layers of membranes (thin, protective layers)
• the hard bones of the skull and backbone

The brain

The brain is made up of different parts. These include the:

• cerebrum
• cerebellum
• thalamus
• hypothalamus
• brainstem

The cerebrum is the largest part of the brain. It controls intelligence, memory, personality, emotion, speech, and ability to feel and move. It is divided into left and right hemispheres (halves), which are linked by a band of nerve fibres in the centre of the brain called the corpus callosum.

Each hemisphere is divided into 4 lobes, or sections, which are all connected.

• The frontal lobes control movement, speech and some of the functions of the mind such as behaviour, mood, memory and organisation.
• The temporal lobes play an important role in memory, hearing, speech and language.
• The parietal lobes play an important role in sensation and in an understanding of numbers, awareness of the body and feeling of space.
• The occipital lobes process visual information from the eyes.

The central nervous system works by sending and receiving messages to various parts of the body. The brain is constantly in contact with all parts of the body, sending instructions via the axons and receiving feedback from the senses. The axons work by carrying these messages as electrical currents or nerve impulses.

Outgoing messages are sent along pathways from the brain to the muscles of the body. These messages activate the muscles. The neurons that make up these pathways are called motor neurons.

Incoming messages are sent along pathways from the senses to the spinal cord and brain. The neurons that make up these pathways are called sensory neurons.

There are many medical conditions that affect the central nervous system. These conditions can be divided into different categories:

• Vascular disorders affect blood flow within the nervous system, and include stroke, transient ischaemic attack (TIA), subarachnoid haemorrhage, subdural haemorrhage and hematoma, extradural haemorrhage.
• Infections including meningitis, encephalitis and epidural abscess.
• Trauma for example, physical damage from accidents or injuries.
• Degenerative diseases affect the structure of the nervous system, and include multiple sclerosis, Alzheimer's and Parkinsons
• Tumours including cancerous and non-cancerous growths.
• Autoimmune disorders occur when the immune system produces antibodies that wrongly attack the body's own cells.

Good nutrition plays an important role in shaping your brain health throughout your life. It's important that everyone — from young children to older adults — ensures they maintain a healthy diet. Good nutrition helps prevent vascular (heart and blood vessel) disease, including the blood vessels that supply the brain and nervous system. Preventing nutrient deficiencies can also help maintain good cognitive and mental health.

For more information about the structure of the central nervous system and how it works, visit the Queensland Brain Institute website (Opens in new tab).

Read more on dementia in English (Opens in new tab) and a range of community languages (Opens in new tab) on the Dementia Australia website. You can also call the National Dementia hotline on 1800 100 500.

Do you prefer to read in languages other than English?

Read all about stroke in English (Opens in new tab) and a range of community languages (Opens in new tab) on the Stroke Foundation (Opens in new tab) website. Read more on living well after stroke (Opens in new tab) in easy English (aphasia friendly) and standard English (Opens in new tab). Call the StrokeLine for advice on stroke prevention, treatment and recovery on 1800 787 653.

You can also call healthdirect on 1800 022 222 at any time to speak to a registered nurse (known as NURSE-ON-CALL in Victoria) for more information and advice.