Know Your Nervous System
Photo by  Florence Ivy

Photo by Florence Ivy

I’m kind of obsessed with the nervous system. The autonomic nervous system specifically. And in today’s post, I’m going begin to share why. This will echo and amplify some of what I have talked about in previous posts — especially this one about the window of tolerance — but with more detail about the neurological and physiological underpinnings of our felt sense of regulation. Buckle up, because this is mind-blowing stuff!

the autonomic nervous system

The autonomic nervous system or ANS is part of the peripheral nervous system (as distinct from the central nervous system) and it is responsible — not always solely responsible, but pretty high up in the physiological chain of command — for three main categories of function:

  1. AUTOMATIC BODILY FUNCTIONS: Heart rate, breathing, digestion, metabolism, sexual arousal, hormone release, urination and defecation, tissue repair, sleep-wake cycle, etc., etc.

  2. SURVIVAL RESPONSES: Fight, flight, and freeze.

  3. SOCIAL ENGAGEMENT: Our ability to connect with others and with our environment.

One of the key words above is “automatic.” The ANS functions, for better or worse, without your conscious control. It’s why, when you’re out hiking, you automatically jump out of the way when you see a stick — or is that a snake!?!?! — on the path. Your ANS doesn’t wait around for you to assess the situation and launch a measured response. Instead, your system mobilizes immediately and reflexively in order to protect you from danger. Thanks nervous system!

The ANS also plays a huge role in the physical symptoms of performance anxiety that many of us experience: sweaty palms, dry mouth, shaking, feeling numb or disconnected, etc. As in the snake/stick scenario, this is your nervous system’s way of mobilizing to meet a challenge — or, in the case of feeling numb or disconnected, of shutting down in the face of a challenge. More on that below…

Historically, the ANS has been understood as having two branches that work in balance with one another. One brach, the sympathetic nervous system or SNS, is often associated with “fight or flight” but can be understood more broadly as our mobilization system. The SNS prepares us physiologically for any physically activity including exercise, play, practice, performance, and, yes, survival responses like fighting or fleeing. The other branch, the parasympathetic nervous system or PNS, is often called the “rest and digest” system and helps facilitate rest and relaxation (slowing down) as well as other low energy activities such as nursing a baby, cuddling, or sleeping.

According to this bipartite view, the two branches operate in a reciprocal relationship, balancing activation and relaxation to according to the stimulus at hand. By slowing the physiology, the parasympathetic nervous system acts as a “brake” on sympathetic arousal. When we need to mobilize in order to meet a threat or to engage in some sort of activity, our nervous system releases the brake thereby increasing our sympathetic activation. When we are not under threat, or when it is time to rest and unwind, our nervous system applies the brake to reduce activation and facilitate relaxation. Another way to think of it is that when we have greater physiological activation, the SNS is dominant; less activation means that the PNS is dominant.

So far, this might sound pretty familiar. But wait — there’s more!

polyvagal theory

In recent decades, a more complex view of the ANS has emerged. A leading thinker in this updated understanding is Stephen Porges, a neuroscientist at the Kinsey Institute at Indiana University and in the Department of Psychiatry at the University of North Carolina at Chapel Hill. Porges has dedicated his career to uncovering the neurological and physiological underpinnings of our capacities for defence, regulation, and connection. Polyvagal theory is the culmination of this work.

The model is very detailed and has many layers, some of which I’ll leave for another post (or several…). But even a brief outline will present some intriguing implications for musicians…so here goes:

The two main features of the polyvagal theory which differentiate it from the more traditional view is that 1) in the polyvagal model, the ANS has three branches, not two, and 2) the branches are organized hierarchically rather than in a reciprocal relationship.

three branches, not two

Polyvagal theory identifies a further division of the parasympathetic nervous system into two branches with distinct functions. The “vagal” in the word “polyvagal” refers to the vagus nerve which is the cranial nerve responsible for mediating the parasympathetic nervous system. “Poly” means — you guessed it — “more than one” and refers to the two branches of the vagus nerve: the ventral (or “forward facing”) branch and the dorsal (or “backward facing”) branch. The terms ventral and dorsal refer to the parts of the brain stem in which these branches originate. The ventral vagus emerges from the front of the brain stem and and the dorsal vagus from the rear.

The ventral vagus enervates parts of the body above the diaphragm such as the lungs and esophagus. It also provides nerve supply to the larynx and pharynx and works closely with the nerves that control the muscles of the head and neck, face, and inner ear. As such, it is a key player in modulating facial expression and vocal prosody (variations of rhythm and pitch in speech) and in ability to orient to and within our surroundings. The ventral vagus also plays an important role in the regulation of heart rate and can lower heart rate and blood pressure gently and smoothly. For example, if we narrowly avoid, say, a car accident, we might experience a spike in sympathetic activation in the form of a fast heart beat, laboured breathing, tense muscles, and a sense of hyper-vigilance. When, after a few moments, our heart and breathing rate return to normal, our bodies relax, and our awareness of our surroundings softens, that’s our ventral vagus coming online and returning us to a state of equilibrium. The ventral vagal branch of the PNS supports feelings of safety and security. It facilitates engagement with others, including communication and bonding, and primes us for for learning and growth.

The dorsal vagus is primarily responsible for the control of the organs below the diaphragm although it also interacts with the heart and lungs, albeit in a much sloppier and less nuanced way than the ventral vagus. The dorsal vagal circuit is best understood as the immobilization or conservation system. When the organism is under threat, the dorsal vagus sends blood away from the limbs to the core of the body in order to preserve life. In this state of shut down, the body is effectively immobilized, pain tolerance is increased, and the heart rate and rate of respiration are slowed to a near halt. Maybe you have seen a cat catch a mouse in its jaws. The mouse might look dead but, if the cat puts it down, the mouse will often spring back to life and skitter away. To paraphrase Miracle Max, the mouse wasn’t dead, it was just mostly dead. And while there is a big difference between mostly dead and all dead, they can look very similar. When the cat caught the mouse and it was clear that it (the mouse) would not be able to successfully fight or flee, it shut down. Humans have the same built-in response to overwhelming threat or injury and we see it in shock, fainting, and becoming physically immobilized when under attack. But it’s not always that dramatic: We also see and experience the effect of the dorsal parasympathetic in milder forms such as social withdrawal, emotional numbness, depression, boredom, etc.

It’s evolution, baby

In terms of evolution, the dorsal parasympathetic circuit is the oldest branch of the autonomic nervous system and is present in all primitive vertebrates. The sympathetic nervous system, which is mediated through both spinal and peripheral nerves, evolved next with reptiles. The ventral circuit — the social engagement system — is the newest branch and evolved with mammals. When I said above that the ANS is organized hierarchically, this refers to the fact that, when under threat, the system will revert to more primitive responses in reverse phylogenetic order. So, if a threat cannot be diffused through communication and engagement, the ANS will initiate a fight or flight response. In the event that we are unable to successfully overcome or escape the threat, the system will automatically shut down in a last-ditch effort to prevent further injury and preserve life.

[Sidebar/caveat: There is some debate among evolutionary biologists as to the accuracy the evolutionary underpinnings of the polyvagal theory. It is beyond my expertise to credibly evaluate these arguments. However, there is broad clinical consensus that, at the very least, this framework provides a helpful map for understanding a wide range of physiological and behavioural responses to stress and the effects of such responses on both physical and mental health. Interested readers can consult Porges’ work for a more detailed — like, I’m talking really, really detailed — discussion of the evolutionary basis of the theory.]

sensing threat when there is no threat

At least, that’s how it’s supposed to work. But, we modern humans often, for a whole host of reasons, live with dysregulated nervous systems that mount survival responses when no threat to survival is present. (I’m looking at you, performance anxiety.) Both the sympathetic nervous system and the dorsal parasympathetic nervous systems can be recruited in defence or in service of what Porges calls “health, growth, and restoration.” (Porges, 2011) We need some sympathetic arousal to engage in play, to exercise, and — oh, I don’t know — practice and perform music! Similarly, the dorsal vagal circuit supports many restorative functions such digestion and sleep. So, the trick is to learn how to help the nervous system distinguish between threat and safety so that our arousal levels support the task at hand and, in the bigger picture, our progress towards larger goals. The key here is that we need reliable access to the ventral vagal (or social engagement system) in order to smoothly transition from a state of sympathetic hyper-arousal to a state of relaxed engagement. Without access to the social engagement system, our efforts to “calm down” often either fail — meaning we remain in a state of sympathetic dominance — or provoke a state of shut down which, even if it is mild, often does not optimally support the behaviour we desire to engage in.

But I’m getting ahead of myself. I feel like a diagram might be helpful at this point. The whole thing works kind of like this:


Okay, that’s pretty and all…but…?

I think there are several profound implications for musicians of this understanding of the nervous system. The older, bipartite view gives us a pretty crude way of viewing — and indeed of experiencing — our experience: We’re either stressed or we’re relaxed. Of course, this is an over-simplification of how the system works, even in under old view, but it persists in the way the sympathetic and parasympathetic nervous systems are talked about. The polyvagal theory provides a map for a much more nuanced way of relating to ourselves, others, and the environment.

For example, many of us experience a spike of sympathetic activation prior to a performance. We feel shaky and our mouths get dry, we might need to pee a lot and may experience a surge of energy in our limbs. Our heart rate increases and we may struggle to breathe deeply and fully. These are all ways that our nervous system prepares us physiologically to meet a challenge.

Naturally, though, when we perform, we want to feel as though we are in control of our bodies. So, we may try to calm our physiology through breathing exercises, visualization, etc. But, if we don’t have reliable access to the ventral vagal circuit these efforts can backfire and instead activate the dorsal vagal circuit.

For example, I sometimes hear performers say that they never get nervous before a performance. These same performers also often describe (or exhibit) a lack of connection during performance, or a feeling of being separated from their bodies, the music, or the audience. (Not always, mind you. Some people really don’t get nervous and still remain very connected to themselves, the music, and the audience.) This is sometimes referred to as pre-performance under-arousal and I suspect that in some cases it is a sign that the the performer is not actually “relaxed” but is instead in a state of mild shut down or what is sometimes called “functional freeze”. It can be very frustrating to feel as though you have mastered your nerves (i.e. de-activated the SNS) but that you still aren’t having the kind of performance experience you desire.

My take is that an ideal state for performance for many of us would be a mix of sympathetic and ventral vagal activation. We need some energy in our system in order to be able to meet the challenge of performing, but we also need the social engagement system online in order to connect with the audience, the music, and fellow performers. So, we need tools to help us dial back excessive sympathetic arousal but that help us find a state of engagement rather than a state of shut down. For someone who is already somewhat shut down, it can be very helpful to bring some energy (aka sympathetic activation) into the system through gentle movement while also working to get the ventral vagal circuit online so that the performer experiences a healthy surge of energy in conjunction with the safety and connection of the social engagement system.

we are all special snowflakes

The way our nervous systems assesses and respond to threat vs safety is highly individual and is conditioned by many factors including genetics, family dynamics, trauma history, experiences in educational systems, overall physical and mental health, social supports, etc., etc., etc. Another way of saying this is: Most situations and events are not in themselves stressful (or not) or relaxing (or not); they are not threatening (or not) or safe (or not). It is the nervous system’s response to a situation or event that determines whether it is experienced as stressful, exciting, enlivening, relaxing, threatening, etc. One of the cool things about working with the nervous system is that we can learn to sense and, with practice, shift how our own unique systems respond to experience. We can learn to give ourselves the support we need — and to be skilful about seeking support from others — in order to excel and meet our goals.

That’s a lot to digest! More soon — different ways of looking at this, tools and tricks, deeper exploration. In the meantime, below are some resources you can check out if you want to dive into this stuff now.

Thanks for reading!


Kain, Kathy L., and Stephen J. Terrell. Nurturing Resilience. Berkeley: North Atlantic Books, 2018.

Porges, Stephen W. The Polyvagal Theory: Neurophysiological Foundations of Emotions, Attachment, Communication, and Self-regulation. New York: W.W. Norton, 2011.

Porges, Stephen W. The Pocket Guide to Polyvagal Theory: The Transformative Power of Feeling Safe. New York, NY: W.W Norton & Company, 2017.

go deeper

I have listened to this podcast interview with Stephen Porges several times because it is so juicy.

This one, with Deb Dana, is a little less technical but equally illuminating.

Reflections and Updates

Reflections and Updates

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Some thoughts on trusting the body...