The Peripheral Nervous System

Abstract

The mammalian nervous system is anatomically separated into central and peripheral systems that are functionally intertwined. The central nervous system receives a continuous stream of information about external and internal environmental factors from sensory elements of the peripheral nervous system (PNS), and responds to these stimuli via activation of efferent peripheral neurons. The PNS, in turn, is divided into the somatic and autonomic branches, with the autonomic nervous system being further subdivided into sympathetic and parasympathetic components. The enteric nervous system, which regulates the function of the gastrointestinal tract, is sometimes considered a third branch of the autonomic nervous system. While the parasympathetic and sympathetic branches are anatomically distinct in the periphery, there is extensive overlap between somatic and autonomic centers of integration in the central nervous system.