The spinal cord is composed of a bundle of communicating fibers from
the brain to all parts of the body and possesses the property of reflex activity;
reflex movements e.g. with drawl of hand form hot surface, often defensive in character,
are more rapid than voluntary movements, since the impulses concerned follow a short
path, by-passing the brain.
Autonomic Or Involuntary Nervous System
This system consists of two distinct tracts of nervous tissue, separate from but
dependent on the central nervous system described above.
(i) The sympathetic nervous system is connected to the lungs, the abdominal and
pelvic viscera (the internal organs).
(ii) The parasympathetic nervous system, connected to the eye.
The salivary glands, the heart, the lungs, the abdominal viscera,
the rectum and the urinary bladder.
The sympathetic nervous system prepares the body to meet situations of stress, while
the parasympathetic nervous system control more 'routine' functions .e.g. gastric secretions,
bowel activity, etc.