The anatomy of the nervous system, from the standpoint of development and function . re are no axons, arising from suchcells, in the sympathetic nerve trunks and plexuses. These nerves and plexusesare composed of the following three kinds of fibers (Fig. 256): (1) Preganglionicvisceral efferent fibers, which are of small size and myelinated, have their cellsof origin in the cerebrospinal axis, and terminate in the sympathetic ganglia.(2) Postganglionic fibers, which are for the most part unmyelinated, have theircells of origin in the sympathetic ganglia and terminate in involuntary muscle orgl
The anatomy of the nervous system, from the standpoint of development and function . re are no axons, arising from suchcells, in the sympathetic nerve trunks and plexuses. These nerves and plexusesare composed of the following three kinds of fibers (Fig. 256): (1) Preganglionicvisceral efferent fibers, which are of small size and myelinated, have their cellsof origin in the cerebrospinal axis, and terminate in the sympathetic ganglia.(2) Postganglionic fibers, which are for the most part unmyelinated, have theircells of origin in the sympathetic ganglia and terminate in involuntary muscle orglandular tissue. (3) Visceral afferent fibers, which include myelinated fibersof all sizes as well as many that are unmyelinated, have their cells of origin in 346 THE NERVOUS SYSTEM the cerebrospinal ganglia and terminate in the viscera. The statements con-tained in this paragraph should not be applied without qualification to the ter- Spiiinl ganglionDorsal root Collateral ganglion Gland-,Blood-vessel-, Pacinian corpuscle n smoothmuscleSensory ending Motor ending on smoothmuscle. Ventral rootSplanchnic nerve // ,. Ganglion of sympathetic trunk• fl^~-- Gray ramus(JnM1^- White ramus Sympathetic trunk Dorsal ramus?Ventral ramusjg$ Gland~g? Blood-vessel - White ramusv Gray ramusGanglion of sympathetic trunk Sympathetic trunk Fig. 256.—Diagram showing the composition of sympathetic nerves. Black lines, visceralafferent fibers; unbroken red lines, preganglionic visceral efferent fibers; dotted red lines, post-ganglionic visceral efferent fibers. minal ganglia and plexuses, since it is probable that these contain additionalelements either in the nature of sensory neurons or of a nerve net. ARCHITECTURE OF THE SYMPATHETIC NERVOUS SYSTEM The sympathetic trunks are two ganglionated cords, each of which consistsof a series of more or less segmentally arranged ganglia, bound together by as-cending and descending nerve-fibers and extending from the level of the secondcervical vertebra
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectnervoussystem, bookye
