what are the primary functions of the sympathetic and parasympathetic
Autonomic nervous system
The autonomic nervous system has three branches : the sympathetic nervous system , the parasympathetic nervous system and the enteric nervous system . Some textbooks do not include the enteric nervous system as part of this system . The sympathetic nervous system is often considered the `` fight or flight '' system , while the parasympathetic nervous system is often considered the `` rest and digest '' or `` feed and breed '' system . In many cases , both of these systems have `` opposite '' actions where one system activates a physiological response and the other inhibits it . An older simplification of the sympathetic and parasympathetic nervous systems as `` excitatory '' and `` inhibitory '' was overturned due to the many exceptions found . A more modern characterization is that the sympathetic nervous system is a `` quick response mobilizing system '' and the parasympathetic is a `` more slowly activated dampening system '' , but even this has exceptions , such as in sexual arousal and orgasm , wherein both play a role . 
The autonomic nervous system has three branches : the sympathetic nervous system , the parasympathetic nervous system and the enteric nervous system . Some textbooks do not include the enteric nervous system as part of this system . The sympathetic nervous system is often considered the `` fight or flight '' system , while the parasympathetic nervous system is often considered the `` rest and digest '' or `` feed and breed '' system . In many cases , both of these systems have `` opposite '' actions where one system activates a physiological response and the other inhibits it . An older simplification of the sympathetic and parasympathetic nervous systems as `` excitatory '' and `` inhibitory '' was overturned due to the many exceptions found . A more modern characterization is that the sympathetic nervous system is a `` quick response mobilizing system '' and the parasympathetic is a `` more slowly activated dampening system '' , but even this has exceptions , such as in sexual arousal and orgasm , wherein both play a role .
The sympathetic nervous system is often considered the `` fight or flight '' system , while the parasympathetic nervous system is often considered the `` rest and digest '' or `` feed and breed '' system. In many cases , one system activates a physiological response and the other inhibits it. The sympathetic nervous system is a `` quick response mobilizing system '' and the parasympathetic is a `` more slowly activated dampening system." In sexual arousal and orgasm , both systems play a role .
The sympathetic nervous system is often considered the `` fight or flight '' system , while the parasympathetic nervous system is often considered the `` rest and digest '' or `` feed and breed '' system . In many cases , both of these systems have `` opposite '' actions where one system activates a physiological response and the other inhibits it . A more modern characterization is that the sympathetic nervous system is a `` quick response mobilizing system '' and the parasympathetic is a `` more slowly activated dampening system '' , but even this has exceptions , such as in sexual arousal and orgasm , wherein both play a role .