Sympathetic nervous system (SNS) is one of the three parts of the autonomic nervous system, along with the enteric and parasympathetic systems. Its general action is to mobilize the body's resources under stress; to induce the fight-or-flight response. It is, however, constantly active at a basal level in order to maintain homeostasis.
Parasympathetic Nervous System
The parasympathetic nervous system (PSNS) is one of the two main divisions of the autonomic nervous system (ANS). The ANS is responsible for regulation of internal organs and glands, which occurs unconsciously. The parasympathetic system specifically is responsible for stimulation of activities that occur when the body is at rest, including salivation, lacrimation (tears), urination, digestion and defecation. Its action is described as being complementary to that of one of the other main branches of the ANS, the sympathetic nervous system, which is responsible for stimulating activities associated with the fight-or-flight response. Because of this relationship, the action of the parasympathetic nervous system is often described as "rest and digest".
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