The term motoneuron groups refers to an extensive set of substructures of the cerebrospinal trunk grouped on the basis of connectivity and function. They extend from the hypothalamus rostrally to the lower end of the spinal cord caudally. The 'moto' prefix indicates that their neurons act primarily on the cells of end-organs, such as muscles and glands, rather than other neurons. They are classified into three groups: The neuroendocrine motor zone, the somatic motoneuron pools, and the preganglionic autonomic pools. Functionally they belong to the subcortical motor system ( Swanson-2004 ).