The fibre tracts that carry impulses from the brain to the skeletal muscles are called “motor or descending tracts.” The two major groups are,
• Corticospinal or pyramidal tracts
• Extrapyramidal tracts
About 80% to 90% of pyramidal or corticospinal tracts decussate in the pyramids of the medulla oblongata and descend as the lateral corticospinal tracts. Hence, they are known as “pyramidal tracts.” The uncrossed fibers decussate in the spinal cord, they form the ventral corticospinal tracts.
Thus, the blanks can be filled with corticospinal; lateral corticospinal; ventral corticospinal.