ABSTRACT
There are many hierarchical levels in the mechanisms of control of voluntary movement. At the lowest level there is the motor unit which consists of the motoneurone in the central nervous system and the nerve fibre from it to the hundred or so muscle fibres that it innervates (Fig. E3–1). All movements are made up of ensembles of contractions of individual motor units. Each muscle is composed of many hundreds of these contractual units. There is brief reference to the simplest pathways involved in the reflex control of motor units (Fig. E3–2). At the other extreme of the hierarchy, there is the motor cortex, area 4 of Brodmann’s map, in which again there is a strip display from toes to tongue matching the sensory strip that is just posterior in areas 3, 1, 2 (Fig. E1–1). Pyramidal cells of the motor cortex send their axons to innervate directly or indirectly motoneurones of muscles (Fig. E3–3).
