EXTRAPYRAMIDAL SYSTEM
NOTE: The extrapyramidal system is old and rather diffuse. It is described by Cajal as a caudalward cascade. Control begins in the cortex and relays information to the basal ganglia via the COEPS (cortically originating extrapyramidal system). Information then passes through the caudate, putamen, globus pallidus II and I, through the subthalamic nuclei, substantia nigra on to the red nucleus and finally down the spinal cord via the rubrospinal tract (located just below the corticospinal tract. Additional input is obtained by connections with the thalamic nuclei and the hypothalamus.
The caudate and putamen are newer and inhibitory. The globus pallidus I and II are excitatory.
The substantia nigra is a major component and provides starter impulses to phasic movements.