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Most of our feelings – both physical and emotional – have their origin in the body. That is, the state of our body and its functions drive the state of our emotions and our emotions also affect our body.

What is the system that coordinates this two-way flow of information?

a. The endocrine system
b. The respiratory system
c. The autonomic nervous system (ANS)
d. The cardiovascular system
e. All of the above


The answer is c: The autonomic nervous system

The Autonomic Nervous System (ANS)

The ANS is a complex biological system which allows us to survive by regulating the functions of our internal organs such as the heart, lungs, stomach and intestines. Most of this is done outside of our conscious awareness. But the ANS doesn’t just allow you to survive; it also affects how you feel.

Traditionally thought of as having two divisions – sympathetic (fight or flight) and parasympathetic (rest and digest) – a newer understanding of how the autonomic nervous system functions has been informed by the work of Dr. Stephen Porges and his Polyvagal Theory. Based on four decades of research, Polyvagal Theory describes how the ANS reacts to experiences and challenges in a hierarchical manner. This hierarchy is composed of three neural circuits. These three primary neural circuits of the ANS are affected by two branches of the vagus nerve, which is the tenth cranial nerve. The vagus nerve is an intrinsic component of the ANS and it communicates an extensive range of signals about our state bidirectionally: from the brain to the body and the body to the brain.

The three neural circuits of the ANS

1. Social Engagement System

Important for healthy engagement with the world, the Social Engagement System (SES) interprets cues from our environment like vocal prosody, eye contact, and facial gestures to gauge our level of safety. When the brain/body appraises the environment as safe (through neuroception), defensive responses are inhibited and a calm state emerges. Your heart rate slows, your muscles relax and your breathing becomes more regulated. You can see this in your face and hear it in your voice – both have expression. When you feel this way, you can rest, digest, control your emotions and thinking. You can learn, and you can be social.

The SES is governed by a branch of the vagus nerve – the ventral vagal complex – that originates in the nucleus ambiguus of the brainstem. This portion of the vagus nerve is myelinated making the transmission of information smoother and faster.

2. Immobilization

If we detect a life threat, our response may devolve to immobilization, or freezing behavior (like a deer in headlights). This would engage a more primitive branch of the vagus nerve – the dorsal vagal complex – originating in the dorsal motor nucleus. And the result is a system shutdown that causes fainting, immobilization, or dissociation.

3. Mobilization

When the brain/body perceives a threat, the SES will release the vagal brake to engage the sympathetic system instantaneously in order to support defense rather than health. When this happens, you feel your heart rate increase, your face flush and your palms sweat. Your breathing increases and your body prepares to fight or flee. In this situation, you have no time to think things through rationally and no capacity to be social.

Vagal Tone

The three different circuits above provide the neural regulation of autonomic state. This is not an on/off system; it is a dynamic and fluid interaction. We are constantly adjusting our physiological state to meet the world and our perceptions about it.

Sometimes, however, autonomic state can get stuck in one of these neural circuits. An example is anxiety wherein one is more prone to sympathetic arousal (mobilization)and has less access to the other autonomic states. Good vagal tone promotes homeostasis of the ANS. High vagal tone improves your ability to flexibly shift in and out of different states based on the situation. Low vagal tone is associated with a reduced capacity to respond to stressors appropriately.

How the Safe and Sound Protocol (SSP) can help

The SSP exercises the neural pathways described above associated with regulating autonomic state and social engagement. And just as the brain is plastic and can change based on experience, the ANS is also plastic. The SSP has been shown in peer-reviewed research to significantly increase vagal tone. The result is better control of autonomic and emotional state.

State is critical to how we approach the task at hand. So when your clients have better autonomic state control, not only can they be more socially engaged, they are more open to therapy. Better state regulation can be achieved using the SSP to improve your clients’ experience and their therapeutic outcomes.

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