Section III. THE HUMAN CENTRAL NERVOUS SYSTEM
5-10. GENERAL COMMENTS
The human nervous system is divided into three major divisions: the central
nervous system (CNS), the autonomic nervous system (ANS), and the peripheral
nervous system (PNS). The central nervous system is composed of the brain and
spinal cord. Both the peripheral nervous system and the autonomic nervous system
carry information to and from the central nervous system. The central nervous system
is so named because of its anatomical location along the central axis of the body and
because it is central in function. If we use a computer analogy to understand that it is
central in function, the CNS would be the central processing unit and the other two parts
of the nervous system would supply inputs and transmit outputs. Figure 5-4 shows the
central nervous system.
a. Major Subdivisions of the Central Nervous System. The major
subdivisions of the central nervous system are the brain and spinal cord.
Figure 5-4. The central nervous system (CNS).
b. Coverings of the Central Nervous System. Bone and fibrous tissues cover
the parts of the central nervous system. These coverings help to protect the delicate
tissue of the CNS.