The sympathetic nervous system is one of the two main divisions of the autonomic nervous system, the other being the parasympathetic nervous system. The autonomic nervous system functions to regulate the body's unconscious actions. The sympathetic nervous system's primary process is to stimulate the body's fight-or-flight response. It is, however, constantly active at a basic level to maintain homeostasis. The sympathetic nervous system is described as being complementary to the parasympathetic nervous system which stimulates the body to "rest-and-digest" or "feed and breed".