The Central Nervous System (CNS)

The central nervous system (CNS) is composed of two parts - the brain and spinal cord. Its name is a reference to both parts as an integrated system being central to the body’s functioning. It receives, processes and transmits information to and from the peripheral nervous system.

The brain is divided into three areas - the forebrain, midbrain and hindbrain. The cerebrum, that makes up the composition of a vast majority of these areas, is divided into two cerebral hemispheres.

• the left hemisphere has contralateral control over the right side of the body including its movements, and manages verbal functions, analytical thinking and logical reasoning.

• the right hemisphere has contralateral control over the left side of the body, and manages spatial functions and controls visual spatial tasks.

The spinal cord is a cylindrical structure that extends from the foramen magnum at the base of the brain. It is composed of both grey and white matter, where grey matter is situated around the central canal in the shape of an ‘H’, and white matter surrounding this.

• the central canal contains cerebrospinal fluid, running the length of the spinal cord.

• myelinated fibres are arranged in bundles, referred to as ascending and descending tracts.

  • ascending tracts contain sensory axons that carry impulses towards the brain.

  • descending tracts contain motor axons that conduct impulses away from the brain.

Structures of the Brain