Final answer:
The sympathetic division is known as the thoracolumbar system since its preganglionic fibers originate in the thoracic and lumbar regions of the spinal cord, with axonal connections also in the cervical and sacral regions via the sympathetic chain, unlike the craniosacral layout of the parasympathetic division.
Step-by-step explanation:
The sympathetic division of the autonomic nervous system is referred to as the thoracolumbar system because its preganglionic fibers emerge from the thoracic and upper lumbar regions of the spinal cord. The anatomical layout of the sympathetic nervous system includes a series of ganglia in the sympathetic chain running alongside the vertebral column, with 23 ganglia typically present: 12 thoracic, 4 lumbar, and additional ganglia corresponding to the cervical and sacral regions.
However, the cervical and sacral ganglia are connected not through direct spinal roots but through ascending and descending axonal connections within the chain. This is in contrast to the parasympathetic division, also known as the craniosacral system because its preganglionic neurons originate in the brain stem and sacral spinal cord, with its ganglia located much closer to, or within, the target organs.