Final answer:
The sympathetic division of the autonomic nervous system is also known as the thoracolumbar system because its preganglionic neurons arise in the lateral horn of the thoracic and upper lumbar spinal cord.
Step-by-step explanation:
The sympathetic division of the autonomic nervous system is also known as the thoracolumbar system, based on the region of the spinal cord where its preganglionic neurons arise.
The lateral horn of the thoracic and upper lumbar spinal cord is the central component of this division. Neurons in this region project to ganglia adjacent to the vertebral column through the ventral spinal roots, forming a network of sympathetic chain ganglia.