What Is the Sympathetic Nervous System?

When you are in distress, it triggers the fight-or-flight response

stressed business woman
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Ever wonder what gets your heart pumping while you're watching a scary movie? Or what's responsible for your quick reaction when someone cuts you off in traffic? Or why your brain goes blank and your palms get sweaty when you have to give a presentation to a room full of people? 

The sympathetic nervous system is what stimulates the "fight or flight" response when presented with a threat, which can range from a wild animal chasing you to being faced to confront your fear of public speaking.

When no threat is present, the parasympathetic nervous system allows your body to rest, recover, and digest nutrients.  

The sympathetic nervous system is one branch of the autonomic nervous system—the second branch being the parasympathetic nervous system. The autonomic nervous system involuntarily regulates the functions of your organs, such as your heart, stomach, bladder, and intestines. It also controls muscles in the body. We often do not notice this system at work because it acts reflexively in response to stimuli.

In acutely stressful situations, your amygdala sends the message to your hypothalamus that you're in danger, and your hypothalamus sends adrenaline into your bloodstream. This sets off a number of physiological and hormonal changes, such as dilated pupils, increased heart rate and blood pressure, increased alertness, and heightened senses. In addition, blood sugar and fats are released into your bloodstream for energy, so you can "fight" or "flee" from the danger.

 

In borderline personality disorder, this very well-orchestrated system is more easily triggered, which can cause serious emotional conflict, within and without. 

The Sympathetic Nervous System and Borderline Personality Disorder

Borderline personality disorder (BPD) is a common and disruptive mental illness, affecting millions of people within the United States.

Despite its prevalence, little research has been performed to study the neurological or physiological mechanisms behind BPD. Some scientists have suggested that better understanding the mechanics behind BPD, such as issues with the sympathetic nervous system, may lead to the creation of more effective treatment options. To date, there is no medication approved to treat BPD, unlike other mental disorders.

According to the Diagnostic and Statistical Manual of Mental Illnesses,5th edition, a reference healthcare professionals review when making a diagnosis, those with BPD typically have trouble regulating their emotions. Researchers have hypothesized that this means the sympathetic nervous system in people with BPD may be overly-stimulated, causing intense or irrational reactions. People with BPD tend to display signs of stress longer than others; some studies have found that those with BPD remain in an emotional state 20% longer than other people. 

For people with BPD, minor situations which wouldn't impact other people can cause an extreme physical response. This can create extreme stress and anxiety, even if the stress is caused by delusions. For instance, if a person with BPD believes her partner is going to leave her, she may become panicked and distraught, even if her partner has no intention of breaking up with her.

Her heart may race, she may cry, and she may feel a rush of adrenaline and take a rash action to prevent her partner from leaving. 

The cause of this heightened response is unknown. Some healthcare professionals believe BPD is caused by a mix of biological and environmental factors, including both genetics and how you were brought up. Abuse, trauma, and abandonment have all been linked to an increased risk of BPD, but your family's health history also plays an essential role. 

Sources:

American Psychiatric Association. Diagnostic and Statistical Manual of Mental Illnesses, 5th edition, 2013. 

Austin, M., Riniolo, T., Porges, S. "Borderline Personality Disorder and Emotional Regulation: Insights From the Polyvagal Theory". Brain and Cognition, 2007, 69-76. 

Harvard Health Publications. Understanding the Stress Response: Chronic activation of this survival mechanism impairs health. Updated March 18, 2016. 

Science Daily. Sympathetic Nervous System. 

 

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