The Autonomic Nervous System

The autonomic nervous system consists of the ganglions that are anatomically and functionally connected with the central nervous system through the visceral efferent components of the cerebral and spinal nerves, and the nerves that arise in these ganglions (fig. 1). Afferent cerebrospinal nerve components, both somatic and visceral, are functionally associated with the autonomic nerves. These, however, are not regarded as partof the autonomic nervous system, since they are essential components of the cerebrospinal nerves. The peripheral visceral efferent conduction pathway consists of two neurons, a visceral efferent cerebrospinal nerve component and an autonomic neuron; the former may be designated the preganglionic, the latter the ganglionic neuron. On the basis of the distribution of the preganglionic neurons in the central nervous system, the autonomic nervous system may be divided into (1) the cranial division, which is connected with the brain stem through preganglionic components of the third, seventh, ninth, tenth