Final answer:
The central motor fibers in the spinal cord control the axial muscles of the trunk, which involves movements such as bending and rotating the torso. The ventral horn of the spinal cord contains motor neurons that direct the movement of both axial and appendicular skeletal muscles.
Step-by-step explanation:
In the spinal cord, the central motor fibers are crucial for controlling movement in the body. Specifically, the axial muscles of the trunk are governed by the anterior corticospinal tract. This tract's axons travel through the spinal cord without decussating in the medulla, maintaining an anterior position until they synapse with lower motor neurons in the ventral horn at the appropriate spinal level. Once there, they decussate and cause activation of the axial muscles of the trunk responsible for movements such as bending and rotating the torso.
The ventral horn of the spinal cord is where the motor neurons responsible for directing the movement of skeletal muscles are located. These include not just the axial muscles but also the appendicular muscles in the arms and legs, with control provided by the lateral corticospinal tract. The greater number of muscles in the arms and legs results in wider ventral horns in the cervical and lumbar regions of the spinal cord.