The main role of the central nervous system is to control different activities of the organism, for example the contraction of skeletal muscles; these activities have the generic name of motor functions of the nervous system and the muscles are called effectors because they do activities dictated by nervous signals. The component of the nervous central system which assure the control of the skeletal muscles contraction create the somatic motor system unit. The nervous central system participates in creating the organism motion through some structures whichcontain: cortical areas, basal nucleus, cerebellum, cerebral trunk and spine. While the inferior levels, the spine and the cerebral trunk create instant answers, automatic, the superior level participates in creatingcontrolled conscious motions.
Keywords:- MUSCULAR TONUS
- NEUROMUSCULAR ACTIVITY
- TONUS MECHANISM.