There are two ways of dividing the nervous system. One method is to classify the brain, the spinal cord, and the cranial and spinal nerves together and call them the cerebro-spinal system; and to classify to itself the vast structure of internal nerves that go to the vital organs, calling it the ganglionic or sympathetic system. The other method is to group the brain and spinal cord, calling them the central nervous system. The cranial and spinal nerves are then grouped and called the peripheral system, and the sympathetic is classed by itself and called the sympathetic.
According to the first method, we have two divisions of the nervous system; according to the latter, three divisions. The latter method is more modern, and it is better because it keeps the cranial and spinal nerves clearly before the mind and enables us to refer to them as a group. As a matter of fact, however, there are no such divisions as these in the nervous system insofar as its physiological functioning is concerned, or in its anatomical aspect. The nervous system, from the apex of the brain to the tips of the fingers and toes and on through the plexuses to the glands and vital organs of the body, is mechanically a united whole.
The basic, elemental substances of the brain and nervous system are nerve cells, nerve fiber, and nerve tissue of several kinds. The central nervous system and the ganglia in various parts of the body are full of nerve cells, and we also find one or more individual cells iii the peripheral terminations of certain nerve fibers. The fibers are of two kinds: namely, short association fibers and the longer fibers reaching to peripheral extremities, the latter being bound together in bundles which we call nerves, or nerve trunk lines. No nerve in the body is more than three feet long, each length of nerve being equipped with a receiving and a discharging terminal. When a current is passing over a nerve route, as for instance, from the brain to the big toe, it passes through relay stations, some of which are known as plexuses, while the simpler, non-functioning relay points are called synapses.
The CENTER in the brain which is in control of the NERVOUS ZONE may be out of harmony with the other parts of the zone due to many causes, and when this occurs, certain phenomena may be observed. A correction of the zone will bring about an improvement, not only in the entire nervous system but in various organs associated with the zone.
The spinal cord levels involved with Zone 3 are as follows:
- THIRD CERVICAL
- FOURTH THORACIC
- NINTH THORACIC
- THIRD LUMBAR