The effects of the sympathetic nervous system are essentially opposite of the parasympathetic nervous system. Sympathetic and parasympathetic nervous system are subdivisions of the Autonomic nervous system. The sympathetic nervous system may have various effect such as accelerating heart rate, widening bronchial passages; decreasing motility of the large intestine; constricting blood vessels; increasing peristalsis in the oesophagus; cause pupillary dilation, piloerection and perspiration. The sympathetic nervous system originates in the spinal cord and its main function is to activate the physiological changes that occur during the flight-or-flight response.
