The Nervous System Under Stress or Trauma

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It is an animated video, a useful tool to understand how the nervous system rewires for disconnection as a defense mechanism in response to trauma.


Polyvagal Theory of the Autonomic Nervous System

The Polyvagal theory developed by Stephen Borges in 1995 has given us an opening into the body-mind connection. Imagine going to a cocktail party. You take a look around not recognizing anybody. You have thoughts of not fitting in, you find yourself feeling self-conscious, getting tense, anxious. Now you are deciding whether to stay or not. Then you see a friend come in. Your body all of a sudden relaxes, you smile, and move to meet your friend. You are happy. You feel safe. How did that happen?

The autonomic nervous system is a danger detector, 24/7, continuously scanning for cues of friendliness or lack of it. It is our unconscious surveillance system.

Our nervous system has two branches:

1) Sympathetic Nervous System– Originates in the spinal nerves. It runs by the adrenaline and cortisol hormones. These hormones mobilize us with energy to flee or fight when faced with danger or impending danger. The sympathetic nervous system reaches out to target organs, such as heart, lungs, stomach, bladder with rapid bursts of adrenaline. It leads to increased heart rate, increased respiration, and muscular tension. We are now ready to take action. How do we identify if we are in sympathetic nervous system activation mode? We feel on edge, racy, tight, restless, we exhibit shallow rapid breath, we are worried, jumpy, wired, agitated, impatient, frustrated.

2) Parasympathetic Nervous System – Originates in the cranial nerves. It runs by the acetycholine hormone. The acetycholine slows down the heart rate, slows down respiration, and brings a sense of relaxation and well-being. Vagus is the main nerve of the parasympathetic nervous system. It wanders downward to the heart and the stomach, and upward to the cortex (inserts itself in speech, facial expressions, and hearing). It is the main highway to mind and body connection.


How does the vagus nerve work?

In two ways. 1. Dorsal (reptile branch) – When activated by intense danger, a life threat, the vagus nerve puts us in the freeze or immobilization response, that is, playing dead. When our bodies go into shut down mode like this leads to numbing, immobility, dissociation, lack of energy, social withdrawal, collapsed posture, unresponsive face. We become isolated, putting us at disadvantage in coping.

2. Ventral (social branch) – It coordinates social connection with others for safety, cooperation, and growth. The role of the ventral vagus system is to turn off the fight/flight response when the sympathetic nervous system is activated. The vagus nerve activates us towards safety through social connection. In order to do this the vagus nerve now goes up to the cortex and influences the facial nerves, which in turn influences voice, tone, rhythm, and facial expressions, which allows us to look for cues of safety in others. Cues of safety then turns off the sympathetic nervous system, all is good.

In the example above of the cocktail party, initially the person’s sympathetic nervous system was activated for a flight response in response to not feeling safe. When s/he saw the friend come in, the ventral branch of the sympathetic system then took over and that person was now able to relax.

When we are in the ventral branch setting the heart rate slows down, the eyes soften, the voice has a kind tone, the rhythm is slow. We feel connected, we feel compassion and we want to reach out. We attend to others and we receive care. We are attuned.

How do we know if we are attuned? Through our own body awareness, such as listening to our body language, paying attention to our breath, being aware of the quality of our gaze, our tone and pitch of voice, the speed and content of speech, our gestures and body postures. Is there anything that I am doing non-verbally or saying that might trigger shame, fear in the other person? How can I make this other person feel safe, become open and receptive?

Co-regulation is to be in sync with others, to attune our nervous system to others for safety. We sing together, eat together, dance together, and play together. We feel safe and become creative. Being in nature, and participating in religious practices and icons also activate this co-regulation. When we are in co-regulation mode there is the ability to soothe and be soothed. We are better able to talk and listen because we are not in a state of threat. The meditation practices act to activate this social vagal system.


Trauma disrupts the ventral vagal system.

It creates a setting of distrust and fear. We start to perceive and experience things differently. Neutral faces look dangerous. Over time this becomes a pattern of experiencing the world. The sympathetic system becomes always vigilant and activated. We are always locked in those patterns of fight/flight mode of response. Or the dorsal vagal branch of the parasympathetic nervous system leads to shut down.

People experiencing post-traumatic stress exhibit either of the following:

1. Hyperarousal – People are in a chronic activation of the sympathetic nervous system. They are triggered by dreams, memories, flashbacks, or associated cues. They can’t calm down. They cannot self-regulate. They are always in a mode of vigilance and agitation. It feels safer to be angry and over reactive all the time in order to avoid potential danger. One then softens this chronic stress with alcohol, drugs, food, sex, or any other kind of addiction.

2. Dorsal Vagal activation – People are stuck here, frequently going into numbing, disconnection, avoidance, social withdrawal, feelings of hopelessness and helplessness, and inability to tolerate human contact.

If a threat is perceived we go into fight or flight. If a life threat is perceived we go into freeze. If safety is perceived we go into social engagement.

The goal of therapy is to reduce sympathetic nervous system activity and increase ventral parasympathetic nervous system activity through breath work, relaxation, and socialization.

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