Chapter 2 The somatic motor system

Abstract

Somatic motor system works with the concept that after an interruption of a certain part of “the motor system” the patient cannot voluntarily move particular parts of the body. A description of the somatic motor system is not possible without summarizing the location and function of its “tools”, which are the motoneurons and their premotor interneurons. This chapter emphasizes that the premotor and motoneurons are the tools of both motor systems and not of the somatic motor system alone. In contrast to autonomic motoneurons, which innervate smooth musculature, the somatic motoneurons innervate striated muscles. In mammals the somatic motoneurons are located in various brainstem nuclei and in the ventral horn throughout the length of the cord. The premotor interneurons belong to the so-called basic motor system. In the spinal cord premotor interneurons are found in the intermediate zone and project to motoneurons at the same level or at levels rostra1 or caudal to where the interneurons are located.