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.
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.
c. Cerebrospinal Fluid. The cerebrospinal fluid (CSF) is a liquid that is thought to serve as a cushion and circulatory vehicle within the central nervous system.
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