A nerve cell whose cell body is located in the brain and spinal cord and whose axons leave the central nervous system by way of cranial nerves or spinal roots. Motor neuron supply information to muscle. A motor unit is the combination of the motor neuron and the set of muscle fibers it innervates.
In vertebrates, the term motor neuron (or motoneuron) classically applies to neurons located in the central nervous system (CNS) which project their axons outside the CNS and directly or indirectly control muscles. The term is synonymous with efferent neurons.