The sympathetic nervous system is one of the two divisions of the autonomic nervous system, having fibers that leave the central nervous system, via a chain of ganglia close to the spinal cord, in the thoracic and lumbar regions. Its nerves are distributed to the blood vessels, heart, lungs, intestines, and other abdominal organs, sweat glands, salivary glands, and the genitals, whose functions it governs by reflex action, in balance with the parasympathetic nervous system.