Understanding the ANS: A Developmental and Comparative Approach

The anatomy of the autonomic nervous system is often covered as a series of pathways and rules to be learned, which distinguish the sympathetic, or flight‐fight system, from the parasympathetic, or rest‐digest system. Does this approach create a true understanding of the system? Does it answer questions such as – why is the sympathetic system thoracolumbar in its origin, while the parasympathetic system is craniosacral in origin? Or, why is there no autonomic output from the cervical or lower lumbar‐upper sacral spinal cord? Furthermore, why is the sympathetic system more widespread than the parasympathetic system? What is the logic behind the design of autonomic pathways? A comparative and developmental approach to understanding the anatomy of the autonomic nervous system establishes patterns of design that answer these questions and elucidate the anatomy of the autonomic nervous system, while clarifying its anatomical details.