A to Z of MS Central nervous system

The nervous system is the means by which the body maintains awareness of the outside world through the senses and communicates messages to and from muscles and organs.

The nervous system is divided into two main areas

• the central nervous system (CNS), which consists of the brain and spinal cord and is enclosed within the skull and backbone
• the peripheral nervous system (PNS), which comprises all other nerves.

Central nervous system

The central nervous system receives, processes and stores information and initiates instructions for bodily activities. The central nervous system is divided into two major parts:

• the brain analyses and stores information and directs the actions of the body
• the spinal cord passes information to the brain and is responsible for reflex reactions.

Peripheral nervous system

The peripheral nervous system is the cabling that transmits information to and from parts of the body. There are two main types of nerve in the peripheral nervous system:

• Sensory nerves collect information from the body's sense organs - responding to touch, temperature, pain, position, smell, sound and sight.
• Motor nerves pass messages back from the central nervous system. When information has been processed centrally, these nerves carry instructions for action to the muscles and organs.

Only the nerves in the central nervous system are damaged by multiple sclerosis. Although MS can affect all parts of the body, this is due to the interruption or blocking of nerve messages within the central nervous system. Whilst the messages they carry may be incorrect, the peripheral nerves themselves are not directly damaged by MS.

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