Answer:
The nervous system together with the endocrine system enables the organism to perceive the variations of the (internal and external) to disseminate modifications that these variations produce and execute the answers appropriate to maintain the internal body balance (homeostasis). The autonomic nervous system divides into the sympathetic nervous system and parasympathetic nervous system. In general, these two systems have opposite (antagonistic) functions, they correct the excesses of the other.
For example, if the sympathetic system speeds up too much the heartbeat, the parasympathetic system kicks in, slowing down the heart rate. If the sympathetic system speeds up stomach work and intestines, the parasympathetic comes into action to reduce the contractions of these organs. The sympathetic generally stimulate actions that mobilize energy, allowing the body to respond to stressful situations. For example, the sympathetic system is responsible for the acceleration of heart rate, by increasing the blood pressure, the concentration of blood sugar and by activating the general metabolism of the body. On the other hand, parasympathetic mainly stimulates relaxing activities, such as reductions in the heart rate pace and blood pressure. One of the main differences between the sympathetic nerves and parasympathetic is that the postganglionic fibers of the two systems usually secrete different hormones.
