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NEUROLOGY 





From the description given it will be seen that the largest nerve roots, and 

 consequently the largest spinal nerves, are attached to the cervical and lumbar 

 swellings of the medulla spinalis; these nerves are distributed to the upper and 

 lower limbs. 



Connections with Sympathetic. Immediately beyond the spinal ganglion, the 

 anterior and posterior nerve roots unite to form the spinal nerve which emerges 

 through the intervertebral foramen. Each spinal nerve receives a branch (gray 

 ramus communicans) from the adjacent ganglion of the sympathetic trunk, while 

 the thoracic, and the first and second lumbar nerves each contribute a branch 

 (white ramus communicans) to the adjoining sympathetic ganglion. The second, 

 third, and fourth sacral nerves also supply white rami; these, however, are not 

 connected with the ganglia of the sympathetic trunk, but run directly into the 

 pelvic plexuses of the sympathetic. 



Sympathetic 

 ganglion 



Spinal nerve 



Cell of Dogiel 

 Spinal ganglion 



Sympathetic 

 ganglion 



4 



FIG. 799. Scheme showing structure of a typical spinal nerve. 1. Somatic efferent. 2. Somatic afferent. 3,4,5. 

 Sympathetic efferent. 6, 7. Sympathetic afferent. 



Structure. Each typical spinal nerve contains fibers belonging to two systems, viz., the 

 somatic, and the sympathetic or splanchnic, as well as fibers connecting these systems with each 

 other (Fig. 799). 



1. The somatic fibers are efferent and afferent. The efferent fibers originate in the cells of the 

 anterior column of the medulla spinalis, and run outward through the anterior nerve roots to the 

 spinal nerve. They convey impulses to the voluntary muscles, and are continuous from their 

 origin to their peripheral distribution. The afferent fibers convey impressions inward from the 

 skin, etc., and originate in the unipolar nerve cells of the spinal ganglia. The single processes 

 of these cells divide into peripheral and central fibers, and the latter enter the medulla spinalis 

 through the posterior nerve roots. 



2. The sympathetic fibers are also efferent and afferent. The efferent fibers, preganglionic fibers, 

 originate in the lateral column of the medulla spinalis, and are conveyed through the anterior 

 nerve root and the white ramus communicans to the corresponding ganglion of the sympathetic 

 trunk; here they may end by forming synapses around its cells, or may run through the ganglion 

 to end in another of the ganglia of the sympathetic trunk, or in a more distally placed ganglion 



