Final answer:
Motor neurons that facilitate movement for structures on the back of the body are located in the ventral horn of the spinal cord. They send impulses out through the ventral root to reach skeletal muscles.
Step-by-step explanation:
The motor neurons that direct movement to structures on the back of the body trunk are found in the ventral horn of the spinal cord. These neurons project through the ventral root and join the emerging spinal nerve to reach the skeletal muscles requiring motor input.
The spinal nerves transmit both sensory and motor information, with motor neurons located in the ventral gray matter and sensory neurons in the dorsal root ganglia. It's the ventral horn of the spinal cord that contains motor neurons which innervate the skeletal muscles, responsible for movements including those on the back of the body trunk.