The relationship between the sympathetic and vagus nerves is interdependent and antagonistic. 1. The vagus nerve is the tenth pair of cerebral nerves of the brain including, it is a mixed nerve. It includes parasympathetic nerves, somatomotor nerves, somatosensory nerves, and visceral sensory nerves. Sympathetic nerves and parasympathetic nerves together innervate the activities of the body’s tissues and organs, but are also antagonistic to each other. 2. Sympathetic nerves cause the pupils to dilate, the heart to beat faster, the visceral blood vessels to constrict, and the bronchi to dilate. Parasympathetic nerves cause the pupils to narrow, the heartbeat to slow, respiratory secretions to increase, and the capillaries at the ends of the skin to dilate. The body is maintained in a healthy state by the interaction of the sympathetic and vagus nerves.