Our descending motor pathways can be divided into the lateral and medial motor systems. The lateral motor system is comprised of the rubrospinal tract and the lateral corticospinal tract. These two tracts control extremity movements on the contralateral side of the body. The lateral corticospinal tract appears to be the most important descending motor pathway in the human boady. The medial motor systems are the anterior corticospinal tract, vestibulospinal tracts, reticulospinal tracts and the tectospinal tract. They control neck, girdle, head and axial movements. The play a crucial bilateral role in gait, balance and posture. The six motor pathways are discussed in greater detail below.
Lateral Motor Systems
Lateral Corticospinal Tracts
The lateral corticospinal tracts control movements of contralateral limbs and are the most important motor pathways in our bodies. Half of the nerves originate in the primary motor cortex and the other half originate from the premotor, supplementary or parietal areas. They all pass through the corona radiata as they descend toward the internal capsule. From there they descend through the peduncles and cross to the contralateral side at the pyramidal decussation, prior to descending down the spinal cord.
Rubrospinal Tracts
The rubrospinal tract originate in the red nuclei, cross over in the ventral tegmental decussation and terminate in the cervical spinal cord. These tracts are not entirely understood. They appear to be magnocellular pathways that play a role in movement and possibly recovery of lost motor functioning.
Medial Motor Systems
Anterior Corticospinal Tract
Vestibulospinal Tracts
Reticulospinal Tracts
Tectospinal Tract