The document discusses the autonomic nervous system (ANS), which regulates involuntary body functions. It is divided into the sympathetic and parasympathetic divisions. The sympathetic division uses thoracic and lumbar spinal cord neurons to regulate functions that prepare the body for exertion like increased heart rate. The parasympathetic division uses cranial and sacral spinal cord neurons to regulate resting functions like digestion. Preganglionic neurons in both divisions synapse on ganglia near target organs like the heart, with postganglionic fibers then connecting to organs.