Find out how the autonomic nervous system works beneath the surface to shape your daily experiences, impact behavioral responses and support — or undermine — your overall health.

For therapists - learn the functions of the autonomic nervous system

Whether you're a therapist, counselor, or simply someone curious about the mind-body connection, this post is for you. We'll break down the science and functions of the autonomic nervous system in clear, accessible language so you come away feeling genuinely informed and empowered. If you work with clients navigating trauma, anxiety, stress, or burnout, this is the foundational knowledge that will deepen your practice and change the way you understand human behavior.

And if you're on your own healing journey, you'll find that understanding and befriending your nervous system is one of the most compassionate things you can do for yourself.

Why Nervous System Regulation Is the Foundation of Good Health

Before we dive into the science, let's start with something simple: how you feel right now matters. The tension in your shoulders. The pace of your breath. Walking into this page feeling grounded and curious, or frazzled and distracted.

None of that is random. All of it is your nervous system at work.

Nervous system regulation is one of the most important — and most overlooked — pillars of mental and physical health. When our nervous system is balanced, we can navigate life's challenges with presence and resilience. We sleep better, connect more deeply with others and respond to stress rather than react to it. When it's dysregulated, everything feels harder: relationships become strained, our focus deteriorates and the body holds tension that simply won't let go.

For therapists and counseling professionals, understanding nervous system regulation isn't just clinically useful, it's transformative. The more fluently you can speak the language of the nervous system, the more effectively you can help your clients move from survival mode into genuine healing. This post will walk you through the key concepts you need: the functions of the autonomic nervous system, the vagus nerve, and polyvagal theory. Together, they offer a map for understanding why people feel the way they feel and what to do about it.

The Autonomic Nervous System: Your Body's Invisible Regulator

The autonomic nervous system (ANS) is the part of the nervous system responsible for moderating your body's response to both external and internal stressors. The word "autonomic" tells you something important: this system operates automatically, below the level of conscious thought. You don't decide to speed up your heart rate when you sense danger — your ANS does it for you, in milliseconds.

Functions of the Autonomic Nervous System

The ANS is made up of two primary branches:

The Sympathetic Nervous System — often called the "fight-or-flight" system
The Parasympathetic Nervous System — often called the "rest-and-digest" system

These two branches control multiple organs, working in opposite directions — like two hands on the same steering wheel, pulling in different ways depending on what the body perceives it needs.

Think of the sympathetic system as the gas pedal. When your brain detects a threat — whether that's a car cutting you off in traffic or an emotionally charged conversation with a colleague — the sympathetic nervous system mobilizes your body for action. Heart rate increases. Breathing quickens. Blood is redirected away from your digestive system and toward your muscles. You are, in every physiological sense, ready to fight or flee.

The parasympathetic system is the brake pedal. It calms the body, slows the heart rate, supports digestion, and helps restore a sense of inner ease. When you exhale slowly and feel your shoulders drop, that's your parasympathetic system doing its job.

When the nervous system is healthy, these two systems work in beautiful harmony — revving up when needed and returning to rest when the threat has passed. Our bodies are designed to do this, and revving up when appropriate is a sign of health! We don’t have to be peaceful all the time to be “healthy.” But for many people, especially those carrying the weight of trauma, chronic stress or difficult life experiences, the nervous system gets stuck. The gas pedal stays pressed to the floor or the system shuts down entirely. This is where things get complicated — and where Polyvagal Theory (which we’ll talk about soon) becomes an essential lens.

The Vagus Nerve: Your Body's Communication Superhighway

Running right through the center of this entire system is one of the most extraordinary structures in the human body: the vagus nerve.

The vagus nerve is a complex bundle of nerves consisting of both sensory and motor pathways. It acts as your body's built-in communication superhighway between the brain and the major organs — your heart, lungs, gut, and more. Its name comes from the Latin word for "wandering," which perfectly describes its reach: it meanders from the brainstem down through the neck, chest, and abdomen.

Among other things, the vagus nerve helps regulate heart rate, breathing, digestion, and the inflammatory response. But its most important function — the one that matters most for therapists — is its role in social engagement. The vagus nerve carries the signals that allow us to feel safe in the presence of others: the subtle shifts in facial expression, the tone of voice, the capacity to listen and be heard.

Critically, the vagus nerve is a core component of the parasympathetic nervous system. When it's functioning well, it acts as a natural brake on the stress response, helping the body return to a state of calm after activation. When it's underactive — as is often the case following trauma — people can feel chronically anxious, disconnected, or shut down.

Here's the good news: vagal response is not fixed. It can be strengthened over time through practices like slow diaphragmatic breathing, humming, singing, cold water exposure, and — most powerfully — safe relational connection. This is precisely why the therapeutic relationship itself is such a profound regulator.

Understanding the vagus nerve is what makes Polyvagal Theory so revolutionary — because it explains why these things work, not just that they do.

What Is Polyvagal Theory?

Polyvagal Theory was developed by neuroscientist Dr. Stephen Porges and has been beautifully translated into clinical practice by therapist and author Deb Dana. It has become one of the most influential frameworks in trauma-informed care — and once you understand it, you'll never look at your clients' responses the same way again.

The name "Polyvagal" refers to the multiple pathways of the vagus nerve. Dr. Porges identified that the vagal system is not a single, uniform structure — it has distinct branches that evolved at different points in our development as a species, and each branch governs a different set of responses.

Polyvagal Theory helps us understand how three distinct states of the nervous system shape our wellbeing, our behaviors, and our capacity to connect — and how these states operate in a predictable hierarchy, often visualized as a ladder.

The Three States of the Nervous System

Ventral Vagal: Safety and Connection (Top of the Ladder)
This is the state we're aiming for. When the ventral vagal system is online, we feel calm, present, curious and connected. We can engage with others, think clearly, regulate our emotions and access our creativity and compassion. This is the state in which healing and integration happen.
A healthy nervous system doesn't mean staying in ventral vagal all the time — life naturally moves us up and down. But it does mean having the capacity to return here with greater ease.
Sympathetic: Mobilization and Activation (Middle of the Ladder)
When the nervous system detects a threat, it activates the sympathetic nervous system. Heart rate increases, breath quickens, and the body prepares to fight or flee. In short bursts, this is entirely adaptive — it's our survival system doing exactly what it was designed to do.
The problem arises when this system stays activated long after the threat has passed. Chronic sympathetic activation leaves people stuck in anxiety, hypervigilance, reactivity, and exhaustion. Most people experience this as anxiety, though it can also show up as irritability, restlessness, or difficulty sleeping. For many trauma survivors, this is their nervous system's baseline — not a choice, but a deeply ingrained pattern.
Dorsal Vagal: Shutdown and Freeze (Bottom of the Ladder)
When a threat feels inescapable, when fight and flight don't seem like viable options, the most ancient part of the nervous system takes over: the dorsal vagal branch. This is the shutdown response. People experiencing dorsal vagal activation may feel collapsed, numb, disconnected, exhausted, or frozen. Think of staring blankly at your phone for hours, unable to engage with anything. It's a protective response to overwhelm, but one that can become deeply entrenched.

Understanding these three states gives therapists an entirely new way to understand and be with client behavior. What looks like "resistance" may be a freeze response. What looks like "manipulation" may be a dysregulated sympathetic system. What looks like "not caring" may be dorsal vagal shutdown. When we understand the nervous system, we stop pathologizing and start regulating.

Why Understanding the Functions of the Autonomic Nervous System Matters

Now that we've mapped out the terrain, let's return to the clinical question at hand: why does understanding the functions of the autonomic nervous system matter for therapists?

Because talk therapy alone often isn't enough to help people truly heal.

When clients are in a dysregulated autonomic state — either hyperactivated or shut down — the thinking brain goes offline. Research consistently shows that trauma lives not just in memory, but in the body. The autonomic nervous system carries the imprint of every threatening experience it has ever lived through. And the autonomic system doesn't respond to logical reassurance the way the thinking mind does.

This is where somatic awareness becomes clinically essential — through breath, movement, grounding, and body-based awareness — therapists can help clients shift their autonomic state, creating the conditions for real therapeutic work to happen.

When a client comes in flooded with anxiety, helping them feel their feet on the floor, slow their exhale, or notice the weight of their body in the chair isn't a distraction from therapy. It is therapy. It's using somatic input to gently apply the brake pedal of the parasympathetic system — to move the client from sympathetic activation toward ventral vagal safety, where healing is actually possible.

The ability to weave this understanding of the autonomic nervous system into your practice — to recognize different states, to know which interventions invite regulation, to work with the body as a co-therapist — is what separates good therapy from transformative therapy.

Applying Polyvagal Theory in Your Practice

The Nervous System Reset Course: Essential Training for Therapists

If you've found yourself reading this post and thinking "I want to go deeper with this" — we'd love to invite you to explore our Nervous System Reset course.

Designed by licensed trauma therapist Julie Goldberg — who brings over 15 years of clinical experience with trauma, EMDR, somatic therapy and Polyvagal-informed approaches — this self-paced course offers both a rich educational foundation and guided experiential practice.

The course – built with therapists and healing professionals explicitly in mind – includes five trauma-informed modules, four hours of pre-recorded video, guided worksheets and lifetime access — so you can move at the pace that suits your nervous system and return whenever you need a reset.

Ready to go deeper? Explore the Nervous System Reset course here →

We also offer guidance to therapists setting up in private practice which you can check out here.