Human Anatomy Part 2 - K. A. Dyubenko A. K. Kolomiytsev Yu. B. Chайkovsky 2008

Special Part
Autonomic nervous system, systema nervosum autonomicum
Sympathetic part

The central division of the Sympathetic part of the Autonomic Nervous system is represented by the intermediolateral Cell Column, columna intermediolateralis, of the Spinal Cord at the C_VIII–L_III segments, which houses the sympathetic nuclei, nuclei intermediolaterales (Fig. 204). Preganglionic sympathetic fibers emerge from the spinal cord as part of the ventral roots (Fig. 204 A). Fibers originating from the Nucleus intermediolateralis (Th_1-12, L_1-2) innervate the smooth Muscle of the viscera, the Eyeball, Blood Vessels, glands, and the arrector pili Muscles of the Skin. In addition, vasomotor, pilomotor, and sweat centers are located here. The fibers then separate from the spinal nerve as white rami communicantes, rami communicantes albi, which (in 16 pairs) reach the ganglia of the Sympathetic trunk. Here, some fibers synapse with ganglionic Cells, while others pass through the ganglion to terminate in subsequent Relay ganglia (Fig. 204 A). Postganglionic fibers from each ganglion of the truncus sympathicus (at all levels) proceed in two directions: the first goes to the effector organ, and the second returns to the spinal nerve. The bundle of postganglionic fibers directed toward the spinal nerve forms the unmyelinated gray ramus communicans, ramus communicans griseus (Fig. 204 A). The subsequent pathway of these postganglionic fibers follows the branching of the Spinal Nerves, providing trophic and tonic innervation to the skeletal musculature.

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Fig. 204 A. Diagram of The formation of communicating branches (according to I. Ye. Kefeli)