Chapter 3 Some principles of the spinal organization of the sympathetic preganglionic outflow

Publisher Summary This chapter reviews the spinal cord organization of the sympathetic motor component. It attempts to formalize some general principles of spinal sympathetic organization. The opportunity to attempt such an undertaking is particularly timely, as recently reported anatomical data have provided some critically missing links central to interpreting long-standing physiological observations. Together, the anatomical and physiological data accentuate and highlight the limitations of reflex circuitry intrinsic to spinal cord. Sympathetic preganglionic neurons are frequently referred to as autonomic “final common pathway neurons”. The analogy with spinal somatomotor system is obvious. One thematic undertone of this review is that perhaps the analogy is too imprecise or maybe overemphasized. The chapter emphasizes that spinal autonomic circuits in isolation are, in fact, remarkably rudimentary. Intrinsic spinal circuits cannot, for example, generate patterned sympathetic responses which typically accompany the expression of the fear, orienting or flight behaviors. It aims to discuss four broad principles of organization.