Calming the Nervous System - Part 1: Introduction to Polyvagal Theory

By Patrick Brown, PMHNP-BC

This is part one of a three part education series exploring new ways to understand, measure, and manage our natural response to internal and external stressors. An important note, if at any point you feel a little frozen or shutdown reading about trauma, please pause, take a few deep breaths, a walk if needed, and ground yourself before continuing.

  The cat and the bunny:

When I was five years old I brought a feral tabby cat home to my mother and asked, “Can we keep it?”.  Three years later the tabby cat proudly brought home a token of gratitude - A lifeless baby bunny clenched in her jaws.  She dropped the very still, grey, short haired bunny in front of us, presumably as a gift, as she marched into the kitchen to eat her kibble - Perhaps famished from hunting.  My mother and I turned to look at each other with a combination of horror and awe, momentarily delaying our eyes from moving back down to the still, tiny ball of lifeless fluff at our feet.  Not a few moments after the cat had turned the corner into the kitchen did the lifeless fluff resurrect itself and start darting around the first floor of our house. “He’s alive! How is he alive!?”, my five year old brain pondered aloud.  Mom and I scrambled to scoop up and protect the bunny, but he was too quick. So, we opened the back door, right as the cat rounded the corner to assess the commotion. The bunny darted out the back door, and the cat pounced face first into the glass door. My tabby cat stared through the imprint of her face in the glass as she tracked the bunny, watching it disappear back into the woods. She looked back at us, then back at the woods, then back at us… with a disapproving “meow”.

The nervous system:

It was once thought that there were just two systems of the autonomic nervous system (ANS): The parasympathetic nervous system (PNS), commonly referred to as “rest and digest” (or “feed and breed”), and the sympathetic nervous system (SNS), commonly referred to as “fight or flight”.  But, we now we know there are three systems of the ANS and the third is a mouthful: The Unmyelinated Vagus of the Parasympathetic Nervous System (UVPNS), which we refer to as "numb and glum". 

All three systems are related to the vagus nerve, which is actually a paired set of nerves that comprise the longest nerve system in the body. The vagus nerve connects to multiple organs including the heart, lungs, and digestive track, but the portion of the vagus nerve likely responsible for "numb and glum” does not have myelin. Myelin is a sheath around the nerve, similar to the plastic coating around an electrical wire, allowing electrical currents to zip along a specified pathway. When the wire is stripped of the plastic sheath, or the nerve becomes unmyelinated, the electrical impulse is slowed and disrupted.

Table 1 - Cascading attributes associated with the three systems of the autonomic nervous system.  

“Rest and Digest” or Parasympathetic Nervous System (PNS)

“Fight or Flight” or Sympathetic Nervous System (SNS)

“Numb and Glum” or Unmyelinated Vagus of the Parasympathetic Nervous System (UVPNS)

1. "Rest and Digest" (PNS) 2. "Fight or Flight" (SNS) 3. "Numb and Glum" (UVPNS)

SLEEP (1)Sleeping well (2)Difficulty sleeping (3)Posture collapses

DIGESTION (1)Digestion increases (2)Digestion slows (3)Urinate or defecate

AFFECT (1)Expressive face (2)Anxious or angry (3)Eyes look fixed, spacey COMMUNICATION (1)Social engagement (2)Difficulty communicating (3)Limited brain activity

IMMUNITY (1)Healthy immune system (2)Increased cortisol (3)Limited immune system

PAIN (1)Decreased inflammation (2)Increased inflammation (3)Little or no pain

LISTENING (1)Easier to listen (2)Difficulty listening (3)Limited listening

ACTIVITY (1)Calm and grounded (2)Tense and mobile (3)Slowed and frozen

AWARENESS (1)Curiosity about life (2)Worried about life (3)Limited awareness

The cat and bunny story helps to frame polyvagal theory as an adaptive response to a threat, and perceived threats can be both internal and external. Let’s say the bunny was eating peacefully with his brothers and sisters, in a "rest and digest" state, when his brother smells or hears something and looks up. Suddenly all of the bunnies stop eating and perk up, all at once. The rest of the bunnies did not need to hear the rustling or see the predator to understand there is a possible threat and quickly move into "fight or flight". Let’s say the bunnies then see the cat, and the little bunny hearts start to race faster, circulating oxygen to vital organs connected to the vagus nerve - Muscles tighten, eyes dilate, and adrenaline rushes through the system getting the body ready to move. The bunnies all run in the opposite direction of the cat, but the one bunny is not fast enough. Initially this bunny may try to fight, but when the cat’s jaws are clamped around his neck, blood is diverted away from parts of his brain, decision making activity decreases and the bunny goes limp. This is the "numb and glum" state, which ultimately allows the bunny to survive.

The nature of trauma:

The bunny lived to grace another day with its cuteness, but for all intents and purposes, that bunny had a near death experience.  Everybody (and bunny) is different. While some may develop symptoms of post traumatic stress related to a near death experience, including being on guard, panic attacks, startling easily, social anxiety, and distressing dreams - some people may not have any symptoms at all.  Still, others may only begin to experience symptoms years after the trauma has occurred, perhaps from a reminder of the trauma. Keep in mind, these reminders can be both internal and external.

PTSD runs the gamut of psychiatric symptoms because it encompasses the anxiety and fear associated with the "fight or flight" system and the depressive and dissociative features associated with the "numb and glum" system. People that have experienced trauma commonly feel guilt or shame that they froze perhaps during a sexual assault or in the midst of military combat. It is important for everyone to understand that this frozen states of "numb and glum" is a biological response designed to help us survive (just like the bunny). 

With trauma, panic, anxiety, and mood disorders it may seem impossible sometimes to spend any significant time in the "rest and digest" system. In parts 2&3 of this series we’ll explore ways of managing our nervous system’s responses to internal and external stimuli in ways that are shown to improve our ability to more frequently be in a connection state - present, compassionate, curious, grounded, and joyful. Remember, the first line treatment of PTSD, panic, anxiety, and depression is psychotherapy, though medication has its place. To learn more about PTSD click here.

Reaching out for help is a sign of strength - When you're ready, we are here. Schedule am appointment today to speak with a therapist or medication provider.

 References:

Campbell, A. (2017). Respiratory sinus arrhythmia and PTSD: A meta-analysis. Retrieved from: http://libres.uncg.edu/ir/uncg/f/Campbell_uncg_0154M_12310.pdf

Lexicomp (2019). Evaluation of heart rate variability. Retrieved from: https://www.uptodate.com/contents/evaluation-of-heart-rate-variability?search=RSA&source=search_result&selectedTitle=1~3&usage_type=default&display_rank=1

Pruder M.D., D.; Ing M.D., K; Borecky, A. (2018). “Emotional shutdown: Understanding polyvagal theory”. Psychiatry & Psychotherapy Podcast. 9 July 2018. https://psychiatrypodcast.com/psychiatry-psychotherapy-podcast/polyvagal-theory-understanding-emotional-shutdown

Walker, RJ. (2016). ANS chart. Retrieved from: https://vivifychangecatalyst.files.wordpress.com/2016/10/ans-chartv3ltr.jpg