Is the autonomic nervous system really an on/off switch?

No. As Dr. Keiser explains, 'The fables or the mythology of autonomic systems is this idea of parasympathetic antagonism being number one and then All or Nothing responses being number two. This is not true... fundamentally not true.' The autonomic system has specific pathways that can activate independently — just like you can wiggle your finger without jumping. Different autonomic pathways can be regulated separately.

What does sympathetic dominance actually mean?

The term 'sympathetic dominance' suggests the sympathetic nervous system is simply overactive. But in most POTS cases, what looks like sympathetic overactivity is actually a compensation for an underlying problem — often inadequate cerebral blood flow. The heart rate increases not because the sympathetic system is malfunctioning, but because the brain needs more blood flow. The elevated heart rate is the body's attempt to solve a blood distribution problem.

Why doesn't calming the nervous system fix POTS?

Because the elevated sympathetic activity in POTS is often a compensation, not the root problem. If the heart rate is elevated because the brain isn't getting enough blood flow, suppressing that compensation doesn't fix the blood flow issue — it might even make it worse. As Dr. Keiser explains, 'If you can actually make the system more efficient at distributing blood, then the heart doesn't have to work so hard.' The goal is optimization, not suppression.

The Autonomic System Isn't a Switch (And Why That Matters)

Dysautonomia

Dr. Nathan Keiser

Published on February 13, 2026

Neurological testing showing autonomic pathway specificity at The Keiser Clinic

If you've been told you have "sympathetic dominance" or your nervous system is "stuck in fight or flight," you've been given an incomplete picture.

The autonomic nervous system is more sophisticated than an on/off switch. Understanding this changes how you think about treatment.

The Myth: All-or-Nothing

The traditional story goes like this: Your sympathetic system (fight or flight) and parasympathetic system (rest and digest) are opposites. When one is up, the other is down. In POTS, the sympathetic is "overactive."

This framing is problematic.

“The fables or the mythology of autonomic systems is this idea of parasympathetic antagonism being number one and then All or Nothing responses being number two. This is not true... fundamentally not true.”

A Better Analogy

Think about how your muscles work.

“You are able to sit there and wiggle your finger, but you are also able to dribble a ball and do a layup. All of those require motor pathways — somatic motor pathways — but we don't assume that every time you fire a motor pathway you fire all the motor pathways.”

You can wiggle your finger without jumping. You can blink without swinging your arm. Different motor pathways can activate independently.

The autonomic system works similarly. Different pathways can activate independently. It's not all-or-nothing. Understanding how this applies to hyperadrenergic POTS is especially important.

Why This Matters for Treatment

If you believe the autonomic system is a single switch stuck in "fight or flight," your treatment options look like:

Calm the nervous system
Reduce sympathetic activity
Increase parasympathetic activity

But if you understand the system is actually made of specific pathways that can be independently regulated, your questions change:

Which pathways are affected?
What's causing the coordination error?
What mechanism is actually driving symptoms?

The Real Issue: Coordination

When we see heart rate spike on standing, the question isn't "how do we suppress the sympathetic system?"

The better question is: "What is the heart responding to?"

Often, it's responding to inadequate blood flow to the brain. The heart rate increase is a compensation — not a malfunction. Understanding the root cause of tachycardia in POTS starts with this distinction.

“The reason that we were getting a big increase in this heart rate was because we were trying to make up for not having enough of that cerebral blood flow.”

Suppressing that compensation doesn't fix the underlying problem. It might even make it worse.

From Suppression to Optimization

The goal isn't to shut down parts of your nervous system. It's to help the system work more efficiently.

“If you can actually make the system more efficient at distributing blood, then the heart doesn't have to work so hard and then you can see that in the outcomes.”

When the underlying mechanism is addressed — when blood flow regulation improves — the system often self-corrects. Heart rate normalizes not because we suppressed it, but because it no longer needs to compensate. Understanding what causes cerebral hypoperfusion is key to this approach.

What to Ask Instead

Instead of: "How do I calm my nervous system?"

Ask: "What is my nervous system responding to?"

Instead of: "How do I reduce sympathetic activity?"

Ask: "What mechanism is driving these symptoms?"

Instead of: "Am I stuck in fight or flight?"

Ask: "What can we measure to understand what's actually happening?"

Key Takeaways

The autonomic system is not a simple on/off switch
Different pathways can activate independently — it's not all-or-nothing
"Sympathetic overactivity" is often a compensation for another problem like low cerebral blood flow
Suppressing the compensation doesn't fix the underlying issue
Understanding the mechanism leads to better treatment than simply trying to "calm the nervous system"

Told You're "Stuck in Fight or Flight"?

If calming techniques aren't working and you're ready to find out what your nervous system is actually responding to, a free consultation call can help identify the specific mechanism driving your symptoms.

I'm Ready to Get Better

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