The Nervous System No One’s Explaining: Forget On or Off—It Thrives In the In-Between.
By Jennifer Finch, M.A., LPC, SEP, NCC
February 9, 2025
Have you ever felt that deep, gut-level knowing that something is off, before your mind even catches up? Or maybe you’ve experienced the opposite: just thinking about an upcoming stressful event sends your heart racing before anything has even happened.
What’s going on here?
Welcome to the constant conversation between your vagus nerve (parasympathetic system) and your sympathetic nervous system (fight-or-flight response). These two systems are running the show of your body’s autonomic regulation, but they operate in very different ways. Some messages come from the body up to the brain (bottom-up),while others come from the brain down to the body (top-down). The balance between these two is what keeps us alive, alert, and (hopefully) regulated.
These days, we’re hyper-focused on activating the parasympathetic response. I get it—no one wants to live in a state of chronic stress, wired and exhausted, jumping at every notification like it’s a life-or-death threat. Learning to downshift, relax, and regulate is essential.
But somewhere along the way, we started treating the sympathetic nervous system like the enemy—as if its only job is to send us into a full-blown fight-or-flight meltdown. That’s a mistake.
The sympathetic system isn’t just about escaping a metaphorical tiger. It’s about staying alert, engaged, and capable. It helps us focus, perform under pressure, and build resilience to stress rather than crumbling under it. When trained properly, it allows us to hold intensity without panic, to step into challenges without shutting down.
But instead of strengthening it, we’re dropping it like a bad habit. We talk about “regulation” as if it’s just a matter of flipping a switch from “stressed” to “calm.” That’s not how the nervous system works. It’s not an on-off switch—it’s a dimmer.
Balance isn’t about shutting one system down—it’s about teaching them to work together. If we want true nervous system resilience, we need to train both. Otherwise, we’re just seesawing between collapse and recovery, never actually expanding our capacity to hold life as it comes.
Let’s stop over-correcting and start integrating. Because real strength isn’t in relaxation alone—it’s in the ability to stay steady, no matter what comes next.
Here’s how your nervous system actually works—a breakdown so simple any stress-addled brain can absorb it.
Think of it like a car. Your sympathetic nervous system (SNS) is the gas pedal. It revs you up, gets you moving, sharpens your focus, and prepares you for action. Your parasympathetic nervous system (PNS) is the brake. It slows you down, restores balance, and helps you rest, connect and recover.
But here’s where most people get it wrong: You don’t just slam on the brakes when you’re speeding out of control. You learn to drive.
A well-regulated nervous system doesn’t just flip between acceleration and a full stop. It knows how to modulate intensity, adjust speed, and navigate the twists and turns of life without spinning out.
So instead of obsessing over how to “activate” one system or “turn off” the other, we need to train them to work together. We need to build a nervous system that can handle stress without breaking and find ease without shutting down.
Here’s how. ⬇️
The Vagus Nerve: Your Body’s Built-In Therapist
The vagus nerve (cranial nerve X) is the main player in your parasympathetic nervous system (PNS)—the system responsible for rest, digestion, and emotional regulation. But what most people don’t realize is that it works both bottom-up and top-down to keep you in check.
Bottom-Up: The Gut Talks First (And the Brain Listens)
• A whopping 80% of the vagus nerve’s fibers are afferent, meaning they send sensory information from the body to the brain.
• This means your gut, heart, and lungs are constantly reporting back to the brain about what’s happening inside.
• If you’ve ever had a “gut feeling,” it’s not just metaphorical—your vagus nerve is literally sending signals from your intestines up to your brainstem.
Examples of bottom-up vagal influence:
• The gut-brain axis: Your vagus nerve is the hotline connecting your microbiome to your mood, digestion, and overall well-being.
• Heart rate variability (HRV): The vagus nerve helps regulate how your heart responds to stress and relaxation.
• Interoception: Your ability to feel internal sensations—hunger, pain, anxiety—comes from vagal input.
Top-Down: The Brain Sends Orders (When It Feels Safe)
• The remaining 20% of vagal fibers are efferent, meaning they send signals from the brain down to the body.
• These signals help slow the heart rate, reduce inflammation, and promote a sense of calm.
• This is the system behind breathwork, meditation, and other practices that activate the “rest and digest” response.
Examples of top-down vagal influence:
• Breathing exercises: Slow exhalations stimulate the vagus nerve to tell the heart, “Hey, we’re safe. Chill out.”
• Polyvagal Theory (Stephen Porges): The ventral vagal system (the myelinated part of the vagus nerve) helps us engage socially, make eye contact, and regulate emotions.
In short, the vagus nerve listens more than it talks—but when it does talk, it’s usually trying to calm things down.
The Sympathetic Nervous System: The Body’s Built-In Alarm System
The sympathetic nervous system (SNS) is not a single nerve but a network of neurons that activate fight, flight, or freeze responses. Unlike the vagus nerve, which mostly listens, the SNS is all about reaction.
Bottom-Up: The Body Reacts Before You Know Why
• The SNS receives sensory input from the body (pain, temperature, pressure) and triggers reflexive responses before you’re even consciously aware.
• These signals bypass higher brain functions, making them fast but sometimes inaccurate.
Examples of bottom-up sympathetic activation:
• A sudden loud noise makes you jump before you process whether it’s a threat.
• Touching something hot triggers withdrawal before you even feel the burn.
Top-Down: The Brain Calls the Shots
• The hypothalamus and amygdala control the SNS, sending signals down to the spinal cord to prepare for action.
• This activation releases adrenaline (epinephrine) and norepinephrine, priming the body for fight-or-flight.
Examples of top-down sympathetic activation:
• Thinking about a stressful event makes your heart race, even if you’re safe.
• Performance anxiety: The mere thought of public speaking triggers a physiological stress response.
Let’s compare the two.
Why This Matters: The Balancing Act
Most of us live in a state of sympathetic overdrive. Our modern world keeps us chronically stressed, constantly anticipating threats that aren’t physically present. The vagus nerve is designed to counterbalance this, but if we don’t actively engage it, our bodies stay in a cycle of fight-or-flight.
How to Strengthen Your Vagal Tone (And Regain Balance)
Please note the information provided below is based on current scientific research on vagus nerve toning. It is meant to inform and inspire, not to serve as medical advice. Before diving into any new practices, especially anything drastic like a full-body cold plunge, consider what is right for your unique body, mind, and soul. And, please consult a qualified healthcare professional before making any changes to your health routine.
• Breathwork: Deep, slow breathing with long exhalations stimulates vagal activity.
• Light and gentle cold exposure: Splashing cold water on your face or ending a shower with cold water activates the vagus nerve.
• Humming or chanting: The vagus nerve runs through the throat, so singing, chanting, or even gargling can stimulate it.
• Slow, mindful movement: Practices like yoga, tai chi, or somatic therapy help engage the parasympathetic system.
• Social engagement: Making eye contact, hugging, and engaging in positive social interactions activates the ventral vagal system.
Final Thoughts: Who Wins?
Neither system is inherently “better.” We need both! The sympathetic nervous system to respond to challenges and the vagus nerve to recover and restore balance. But if you find yourself stuck in fight-or-flight, it’s time to recruit your vagus nerve and let your body remember what safety feels like.
After all, survival is great. But so is feeling at peace. But it isn’t an either-or. In fact, if we keep practicing regulating one (the parasympathetic) while neglecting the other (the sympathetic), we actually reinforce the reactivity of the other (in most cases, the sympathetic system). In perfect balance and with deliberate practice, we can maintain a state in the in-between. We can sustain feeling active, engaged, and alert, as well as rested, calm, open, and spacious. Simultaneously.
Be Here. And be Now. Jen
