Technic and Practice of Chiropractic

by Joy Maxwell Loban

In the main these nerves of motion and sensation are arranged as follows:

The Cervical plexus is composed of the intertwining of axons from the anterior primary divisions of the four upper Cervical nerves. Its branches pass to and innervate many voluntary muscles of the neck and side and back of head, and supply sensor fibres to the adjacent cutaneous areas. Branches also communicate with the last three cranial nerves and one long branch, the Phrenic, or Internal Respiratory Nerve of Bell, passes through the neck and thorax to the diaphragm, as its motor nerve.

The Brachial plexus is made up of the anterior primary divisions of the four lower Cervical nerves and the greater part of the first Thoracic. It is distributed chiefly to the voluntary muscles and integument of the shoulder and arm, forearm, and hand, but sends branches to some muscles of the neck and upper back as well. It, like the Cervical plexus, receives branches from, but gives none to, the Cervical sympathetic.

The Thoracic nerves are not arranged in plexiform fashion like those above but pass separately, for the most part, to their destinations. They are distributed to the walls of the thorax and abdomen following the curve of the ribs in direction. The last Thoracic sends one division downward as far as the outer aspect of the ilium.

The Lumbar, Sacral, and Pudendal plexuses are formed of the ventral divisions of the Lumbar, Sacral, and Coccygeal nerves and distribute branches to the integument and voluntary muscles of the lower abdomen, pelvis, and lower extremities. From two of the sacral nerves branches known as “Visceral” pass through the plexus to terminate in the walls of the uterus and rectum.

All of the thoracic nerves and the first and second, sometimes the third and fourth, lumbar give off branches to the sympathetic ganglia, known as white rami communicantes.

Direct Distribution of Cranial Nerves

The distribution of the 12 pairs of cranial nerves is not so definitely to voluntary muscles and to areas from which conscious sensation is to be derived as is the case with the spinal, although the cranial nerves present many analogies with the spinal and there is abundant reason for considering them as in one series of 43 pairs. There is direct distribution of some cranial nerve fibres to secreting glands, but these fibres are probably merely derived from sympathetic trunks and carried in company with the axons of cranial origin. There is also some direct distribution of cranial nerve axons to visceral walls made of non-striated muscle, as in the case of the vagus distribution to the respiratory and alimentary tracts and that of the spinal accessory to the heart. This is a resemblance to the sympathetic.

The cranial nerves carry afferent impressions from the special sense organs, except those of the sense of touch, which function is divided with the spinal nerves.

Various intercommunications exist between the cranial and sympathetic divisions of the peripheral system, by means of which axons starting with one division may be finally distributed with another, or by which an axon of the sympathetic may pass to one of the sensor ganglia of the cranial system and influence its nutrition and condition, and therefore its power to act. There is a limited intermingling of spinal fibres with the lower cranial.