The relationship between the sympathetic and parasympathetic nervous system components may be best summed up as being one where they complement each other. The sympathetic nervous system is the part that handles the bodys quick responses to external stimuli, such as the storied "fight or flight" response. It does this by a series of pre- and post-ganglionic connections between neurons. Acetylcholine is used as a neurotransmitter, which attaches to nicotinic acetylcholine receptors on other neurons. The parasympathetic nervous sytem, which operates in much the same process described for the sympathetic nervous system, is responsible for body processes while the body is at rest. Body functions such as salivation, lacrimation (production of tears), urination, digestion, and defecation fall under the control of the parasympathetic nervous system. A good way to remember the tandem way these two system operate is the sympathetic nervous system is the accelerator of the body, while the parasympathetic nervous system is the brakes of the body.