2 Anatomy of IOM 13 Rostral Posterior (toward the back) Dorsal Ventral Caudal Anterior (toward the front) Rostral Ventral Dorsal Caudal Fig. 2.3 A lateral drawing of the human trunk with arrows indicating the relative terms of anterior and posterior Fig. 2.4 A drawing of the neuraxis illustrating the relative terms rostral, caudal, dorsal, and ventral with the neuraxis (most notably as you approach the level of the cerebral cortex). The dorsalâventral or anteriorâposterior plane is perpendicular to the rostralâcaudal axis at any given point (Fig. 2.4). Pathways moving from the peripheral nervous system toward the central nervous system are termed afferent pathways. These pathways are sensory. Pathways that travel from the central nervous system out toward the periphery are termed efferent pathways. These pathways carry motor information. sists of all of the nerves that come off of the brain (cranial nerves) and spinal cord (spinal nerves), nerve plexuses, and peripheral nerves innervating the various structures of the body. Functional divisions of the nervous system include the somatic and autonomic divisions. The somatic nervous system governs voluntary actions and provides motor output through the action of the skeletal muscles. We will spend the majority of time discussing the somatic nervous system, as it is the division that is amenable to neuromonitoring. However, a brief consideration of the autonomic nervous system is warranted. Organization of the Nervous System Autonomic Nervous System The nervous system can be divided both anatomically and functionally. Anatomically we divide the nervous system into the central and peripheral nervous system. The central nervous system (CNS) consists of the brain, spinal cord, and the retina. The peripheral nervous system (PNS) con- The autonomic nervous system governs âautomaticâ visceral or vegetative functions and operates generally at the unconscious level. Examples of functions under autonomic control include respiration, heart rate, digestion, and sexual arousal.