Describe the complementary relationship that exists between the sympathetic and parasympathetic systems. What function do these systems carry out in the body?
The sympathetic and parasympathetic systems often operate in opposition to each other. Many internal organs are stimulated by both systems. When one stimulates an organ, the other tends to depress the organ. The sympathetic system often produces the "fight-or-flight" reactions in organs preparing the organism for emergency situations. The parasympathetic system tends to inhibit these reactions. Thus, the response of an organ depends on the proportionate strength of stimulation supplied by each system at any given moment. It should be noted that parasympathetic and sympathetic enervation in some organs produce complementary, rather than opposing effects.
