Chapter 3 - Peripheral nervous system

Abstract

Publisher Summary This chapter discusses the structure and function of peripheral nervous system. Peripheral nerves comprise fasciculi of nerve fibers, myelinated and non-myelinated, enclosed in three sheaths of connective tissue. The nerve trunks are surrounded by epineurium, fasciculi by perineurium, and individual nerve fibers by endoneurium. According to axonal diameter and the speed of conduction, nerve fibers may be divided into three main groups: A, B, and C. During development, axons leaving the spinal cord as ventral roots, unite with peripheral processes of dorsal root ganglia to form segmental spinal nerves; they are accompanied at regular intervals by peri-axonal Schwann cells. The chapter discusses the peripheral receptors and effectors. Receptors are transducers, converting mechanical and other stimuli into electrical impulses. They are classified as—superficial exteroceptors responding to external stimuli; deeper proprioceptors stimulated by movement, pressure, and change of body position; and interoceptors from viscera and blood vessels. Somatic effectors are the terminals of myelinated axons of motor neurons that pass without interruption from spinal cord to striated muscle. Visceral effectors are supplied by non-myelinated axons from cells in the autonomic ganglia.