GENERAL PRINCIPLES OF THE CONTROL OF VOLUNTARY MOVEMENTS
The commands for voluntary movement originate in the cortical association areas (see Figure 5.44). The movements are planned in the cortex, as well as the basal ganglia and part of the cerebellum. The com-mands are then relayed via the corticospinal tracts (from the cortex to the spinal nerves) and the corti-cobulbar tracts (from the cortex to the cranial nerves) to the lower motor neuron that supplies the muscle. As the movement occurs, receptors in the muscle— the muscle spindle, Golgi tendon organ, joint recep-tors, and those in the skin—are stimulated. This feed-back information is relayed back via sensory nerves to the cerebellum and the motor cortex and the move-ments are adjusted to make it smooth and precise.
The neurons from the cerebellum project to the brainstem, from which they descend to the lower mo-tor neurons via the rubrospinal, reticulospinal, tec-tospinal, and vestibulospinal tracts.