The sympathetic nervous system, the parasympathetic nervous system, and the enteric nervous system comprise the autonomic nervous system in the body. It operates through a network of neurons throughout the body, which originate inside the vertebral column and extend down to the third lumbar segment of the spine.
The autonomic nervous system is continuously active and is responsible for unconscious regulation of our glands and organs. The sympathetic nervous system takes charge of "fight or flight" activities, such as pupil dilation, increased heart rate, increased sweating, and increased blood pressure. These activities are complementary to those of the parasympathetic nervous system, which activates processes associated with the "rest and recover" response, such as such as salivation, tears, sexual arousal, urination, digestion and defecation.
The natural opposition of the sympathetic and parasympathetic nervous systems provides both quick responses when needed, and slower responses for less urgent needs. These systems act something like an accelerator and a brake for our body, and help maintain balance, or "homeostasis". The sympathetic system is like the accelerator, and its responses are carried out all at once, rather than as needed with the parasympathetic nervous system. It is usually activated in response to stress, or anything your body perceives as threatening. In order to maintain the fight or flight response, your body must shut down much of the "rest and repair" activities needed to heal injury. This is where chiropractic care can be helpful.
Chiropractic adjustments have been known to affect the autonomic nervous system by helping to down-regulate the sympathetic nervous system and promote parasympathetic activity. For example, pain receptors are part of the sympathetic nervous system. A chiropractic adjustment may be able reduce the firing of the pain receptor by decreasing input to the spinal cord, thus reducing the sensation of pain.
In general, you want your body to be in a state of rest in order to heal, repair tissues, and grow new tissues. This resting state is also supportive of the immune system, which is highly sensitive to stress and stress hormones. We are more susceptible to illness when we are stressed, because stress hormones are released as part of the fight or flight response. Those hormones are helpful when we need them to deal with a real crisis, but when they are chronically activated due to personal or physical stress, they lower our defenses against illness and disease.
Your chiropractor will conduct a thorough examination and history to determine if there is an imbalance between your sympathetic and parasympathetic systems. Any imbalance will be contributing to your health problems and often can be restored to balance through chiropractic adjustments, as well as additional stress-relief techniques.