Final answer:
The sympathetic division of the ANS, also termed the thoracolumbar system, initiates in the lateral horn of the thoracic and upper lumbar spinal cord. It modulates 'fight or flight' responses and influences diverse organ systems through its preganglionic fibers' multiple branches.
Step-by-step explanation:
The sympathetic division of the autonomous nervous system, also known as the thoracolumbar system, originates from the lateral horn of the spinal cord in the thoracic and upper lumbar regions. This system is responsible for the 'fight or flight' response, controlling bodily functions that are not consciously directed, such as the heart rate, digestion, and respiratory rate, among others. Neurons from the lateral horn transmit signals to various ganglia including the sympathetic chain ganglia or collateral ganglia, influencing organ systems throughout the body.
The autonomic nervous system (ANS) is divided into the sympathetic and parasympathetic systems, with the sympathetic division prepared to respond to stress or emergencies. In contrast, the parasympathetic division, or craniosacral system, influences bodily functions aiming at conservation and restoration of energy. The sympathetic nervous system's wide range of influence can be observed in how a single preganglionic neuron can have 10-20 targets, reflecting its divergent nature and preparing the body for rapid, global responses to stimuli.