extrapyramidal system
- All the central nervous system (CNS) nuclei and axon tracts that generate and transmit motor programs outside the corticospinal tracts. The major extrapyramidal nuclei include the basal ganglia and the red nucleus, including the ansa lenticularis and the rubrospinal tract.
- Certain CNS nuclei and axon tracts in the brain that control and modulate movement but do not directly synapse on motor neurons. The main extrapyramidal nuclei are the basal ganglia. The main extrapyramidal tracts form a loop: axons from the motor cortices of the cerebral hemisphere synapse in the basal ganglia, axons from the basal ganglia (via the ansa lenticularis) synapse in the ventral anterior (VA) and ventral lateral (VL) nuclei of the thalamus, and axons from the VA and VL nuclei synapse back in the motor cortices.