Read Time: Est 10-12 Minutes
Trauma Responses: The Ancient Predilection to Survive
Trauma affects people in a wide variety of ways, with responses ranging across a spectrum from fight and flight to freeze and shutdown. Dr. Stephen Porges’ Polyvagal Theory sheds light on the biological systems that drive these observable behaviors, revealing how our autonomic nervous system instinctively reacts to perceived threats.
By understanding the mechanisms behind our trauma responses-rooted in ancient survival systems-we can begin to untangle feelings of shame or confusion surrounding our reactions.
This knowledge is a crucial step toward healing, as it empowers us to view these responses with compassion and recognize them as natural, adaptive efforts to protect ourselves-allowing us to approach recovery with greater compassion and self awareness.
Additionally, if you are familiar with the Window of Tolerance, the Polyvagal Theory can provide a framework for understanding why, after the nervous system has been dysregulated by trauma, people may more easily shift into states of hyperarousal (sympathetic) or hypoarousal (dorsal vagal shutdown).
The Autonomic Nervous System
In order to understand the Polyvagal Theory, which consists of Porges’ three levels of safety, you must first have an understanding of the mechanics of the Autonomic Nervous System (ANS).
This system is comprised of two branches, the sympathetic, and parasympathetic, and each branch functions in accordance to our breathing and emotions. While both are always active to some extent, their roles shift dramatically in response to perceived threat.
The Sympathetic Nervous System (SNS) is responsible for activation and arousal, including the fight or flight response. This system maintains a baseline state of alertness and metabolic readiness, regulating heart rate, blood pressure, and energy mobilization.
The SNS is modulated by inhaling, as well as by emotions like fear, anxiety, or excitement, which signal the body to increase alertness and readiness in response to perceived challenges.
The Parasympathetic Nervous System (PNS) supports “rest-and-digest” functions, promoting recovery, digestion, wound healing, and conservation of energy. Under stress, this system is responsible for the freeze response.
The PNS is modulated by exhaling, as well as by emotions like calmness, contentment, or safety, which signal the body to relax and restore balance after stress.
Additionally, the ventral vagal and dorsal vagal nerves are components of the vagus nerve, a critical part of the PNS.
The ventral vagal system is the evolutionarily newer branch. In daily life, it is primarily responsible for facilitating social connection, physiological regulation, and emotional resilience.
In contrast, the dorsal vagal system is the evolutionarily older branch that governs the deeper, unconscious processes that keep us alive. In daily life, its key functions are energy conservation, digestive processes, and protective monitoring (quiet withdrawal or “zoning out” to protect the body from overwhelm).
Throughout this post, you may see me refer to these structures as either a ‘complex’ or a ‘system.’ The ventral vagal or dorsal vagal ‘system’ refers to the function (e.g., promoting connection or shutdown), while the ‘complex’ refers to the specific brain and nerve structures behind that function.
Fire Alarms, Brakes, and Emergency Switches: How Your Nervous System Responds
It may be helpful to think of your SNS as a ‘fire alarm’ system that activates during stress in order to enable you to fight or flee from danger. The ventral vagal system can be thought of as the “brake system” that keeps the fire alarm in check. This is vital because without it, every small stressor would send us into a state of fight or flight. The dorsal vagal system can be thought of as our ancient emergency off switch. If the threat is too big, we shut down to conserve energy.
These systems work together to help us adapt to our environment: the SNS will get you moving if there is danger, and the ventral vagal system will return you to baseline when the threat has passed. However, the ventral vagal system doesn’t just keep the SNS in check, it actively promotes safety and connection. This helps us recover from stress and engage socially.
Now that we have outlined the roles of the sympathetic and parasympathetic systems, it will be easier to understand how these responses show up during trauma.
The Polyvagal Theory
The Polyvagal Theory states that the autonomic nervous system regulates three fundamental physiological states, and the level of safety at any particular time determines which one is activated.
These levels are the social engagement system (supports adaptive coping, governed by the ventral vagal complex), fight or flight (activates mobilization responses, governed by the SNS), and collapse (activates immobilization responses, governed by the dorsal vagal complex).
The First Level of Polyvagal Theory: The Social Engagement System
The social engagement system, driven by the ventral vagal complex, is a network of neural systems that regulate how we interact with others. When the nervous system perceives a potential challenge, the ventral vagal system is activated to maintain calmness and assess the situation.
The goal of this phase is to use connection and communication to resolve the issue before more intense stress responses are triggered.
Example: If you’re feeling uneasy in a new environment, making eye contact with a friendly person or engaging in light conversation can reassure you that the situation is safe.
You can think of this phase as a safety net. If the ventral vagal system succeeds in maintaining a sense of safety through connection, the body remains calm. However, if connection fails (e.g., no one provides comfort or validation, or the threat escalates), we move on to the second level.
The Second Level of Polyvagal Theory: Fight or Flight
In this stage, the hypothalamus will activate the sympathetic nervous system (SNS) to initiate the fight or flight response. This will result in a release of adrenaline, noradrenaline, and cortisol that will prepare you to either run or face the threat.
Physiological Effects:
- Increased Heart Rate: Delivers more oxygen and nutrients to muscles and vital organs.
- Dilated Pupils: Enhances vision by allowing more light into the eyes.
- Redirected Blood Flow: Blood is shunted away from non-essential systems (e.g., digestive system) toward muscles and the brain.
- Increased Respiration: Allows for greater oxygen uptake to fuel muscular activity.
- Energy Mobilization: Stored energy is released to fuel muscles for action.
If this stage results in a successful escape from harm, the parasympathetic nervous system (PNS) will step in to restore the body to a state of rest and repair. However, if it fails, or we have perceived that there is no way to escape from the threat, we will initiate the third level.
The Third Level of Polyvagal Theory: Dorsal Vagal System
In the third level, the dorsal vagal system can be thought of as our “emergency shutdown switch.” This response is adaptive and exists on a spectrum of healthy regulation in daily life, to extreme activation in the face of a life-threatening or inescapable threat.
It’s important to note that the dorsal vagal response does not always occur after fight or flight. While the nervous system often tries to move from connection (ventral vagal) to fight or flight (SNS) before reaching shutdown, this is not always the case. In some situations, your body might bypass fight or flight entirely and move straight to dorsal vagal shutdown.
Moderate Activation (Freeze)
In the face of significant stress, the dorsal vagal system can initiate a “moderate activation,” or the freeze response. This is a survival strategy where the body becomes immobilized to avoid further harm or conserve energy.
Physiological Effects:
- Heart rate slows significantly.
- Breathing becomes shallow.
- The body feels “heavy” or paralyzed.
Often described as “playing dead,” in evolutionarily terms, this state may mimic a non threatening presence to predators. It may come with a profound sense of hopelessness or an inability to take action despite wanting to, and dissociation, a detachment from reality, emotions, or one’s own body.
While the freeze response is a part of the dorsal vagal system, it is distinct from the “collapse” response in that it involves both sympathetic and parasympathetic action. It represents a blend of sympathetic arousal and dorsal vagal immobilization, leaving the body prepared for action but unable to act.
Extreme Activation (Collapse)
Dominated by dorsal vagal activity, this system is most likely to engage when we are physically immobilized, or in situations of extreme or inescapable threat, where survival feels impossible. Commonly known as the “collapse” response, in this state the dorsal vagal response triggers a complete shutdown of bodily functions.
At its most extreme, this response acts as the body’s way of conserving energy and reducing pain in preparation for enduring a life-threatening situation. In cases where survival may not be possible, it can also serve to ease the transition by dulling pain and detaching from the overwhelming sensations of the moment.
Physiological Effects:
- Heart rate and blood pressure drop to critically low levels (bradycardia).
- Metabolic activity slows dramatically.
- Fainting or loss of consciousness may or may not occur.
- The body may release endorphins to dull pain, preparing for potential injury or death.
In this state, the body and brain prioritize survival over encoding new memories. This can result in gaps or a complete absence of memory of events during the shut down. In order to protect your psyche, it may put a “pause” on your conscious awareness-resulting in extreme dissociation or cognitive shutdown. Individuals may appear docile or compliant, doing only what is absolutely necessary to avoid further harm.
Example: A person caught in a physically overpowering situation (e.g., an assault) might go limp, appear emotionally vacant, and stop struggling, even though they are still conscious.
If the threat passes, the body will gradually “wake up” and begin to re-engage with its environment. While higher-level thinking and memory encoding often remain offline, actions like walking or following simple directions can happen reflexively, without full awareness or control.
How This Knowledge Can Help Trauma Survivors
A couple weeks before my assault, I happened to have a long conversation at work about self defense techniques and different ways to protect yourself in the face of an attacker. So in the beginning, I felt shame and disappointment in myself regarding the way that I reacted. I blamed myself and felt that he couldn’t have asked for an easier victim, as I believe I fully shut down, and likely became compliant, almost immediately.
Equipped with the self defense knowledge, I wished that I had walked away with a fight or flight story-where in a rush of adrenaline I had put up a fight and escaped indisputable harm. Realistically, I was on a dirt road somewhere in a country I wasn’t familiar with-escape was unlikely, and my body reacted accordingly.
I will probably never know the extent of what happened to me over the 2.5 hours I was in the car. However, learning about processes like the Polyvagal Theory helped me to at least further my understanding of what was likely my physiological state. As I have learned more about it, I have come to peace with the fact that in that moment, my body knew exactly what it needed to do to survive something horrific. I have accepted that in order to protect me, my brain may have never encoded those memories at all.
It’s common to walk away from a traumatic event with shame or confusion regarding the way that you reacted. However, in these moments we often instinctively resort to ancient and evolutionary survival techniques. Your responses were not a choice but an automatic reaction from your nervous system, designed to protect you in the face of danger. Understanding this can help release feelings of shame and foster self-compassion as you begin to heal.
Much of my information for this post was pulled from the book “The Body Keeps Score” by Bessel van der Kolk. If you are interested in learning more I would highly recommend you read it. However, keep in mind that the book can be triggering at times and may not be suitable for all readers.
Other Sources
National Library of Medicine – Polyvagal Theory: A science of Safety
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