A bear will kill you faster than a bacteria. Every time.
That sentence explains more about chronic fatigue, poor digestion, frequent illness, and brain fog than it has any right to, so it's worth unpacking.
Your body has a survival mode. When it detects a genuine threat, it makes a series of rapid decisions about resource allocation — what to fund and what to defund. Those decisions are not arbitrary. Each one is correct for a short, dangerous situation.
The trouble begins when the situation never ends.
What Does the Body Fund During a Threat?
When your sympathetic nervous system activates, a specific set of changes happens at once.
Stress hormones rise — adrenaline first, then norepinephrine, and with sustained activation, cortisol. Your heart rate and blood pressure increase. Muscle tone increases. Reflexes sharpen. Energy is mobilized out of storage and made immediately available.
All of that is appropriate. Adrenaline is essentially jet fuel poured onto every one of those responses. If you need to fight something or outrun it, you want full power available right now, and your body delivers it.
That's the funding side, and it's not free. It has to come from somewhere.
What Does It Defund, and Why Is Each Choice Correct?
Here's where the bear becomes useful.
**Your immune system is suppressed.** That sounds self-destructive until you consider the timeframe. You could be carrying a significant bacterial infection right now, and over the next five minutes that infection will not kill you. The bear will. Your immune response is genuinely irrelevant to surviving the next five minutes, so the resources it was using get redirected to something that matters more urgently. You can deal with the bacteria once you're out of the tree.
**Digestion shuts down.** Absorption of nutrients slows. So does elimination. Extracting energy from the meal you ate two hours ago is a long-term project, and long-term projects are exactly what get suspended during an emergency. Blood is pulled away from the digestive tract toward muscle.
**Healing slows.** Tissue repair is another long-horizon investment. It contributes nothing to the next few minutes and gets deprioritized accordingly.
**Cognitive function drops.** Blood flow and neural activity shift away from your frontal cortex — the part responsible for planning, reasoning, and abstract thought — and toward more primitive structures that handle immediate reaction.
This last one has a demonstration everyone can verify from memory. If someone jumped out and startled you badly, and then immediately asked you to solve an algebra problem, you couldn't do it. Not because you don't know algebra. Because in that moment your brain has deliberately withdrawn resources from the system that does algebra.
**It's very hard to do algebra while you're being attacked by a bear.** That isn't a failure of the brain. That's the brain working exactly as designed.
Every one of those shutdowns is intelligent triage. All of them are correct — for about five minutes.
What Happens When the Response Never Ends?
Now hold every one of those settings in place for months or years.
The funding side runs continuously. You're burning energy at an elevated rate constantly, with nowhere to put it and no recovery period. That depletes your reserves without replenishing them. The result is the pattern people describe as burning out and crashing, and eventually as chronic fatigue — being exhausted and wired at the same time, which sounds contradictory until you understand that both are the same setting.
The defunding side runs continuously too. Immune suppression stops being a five-minute trade and becomes a standing condition, so you get sick more often and take longer to recover. Digestion stays throttled, so absorption suffers regardless of how carefully you eat. Healing stays deprioritized, so injuries linger. Cognitive function stays reduced, so thinking feels effortful and unreliable all the time.
Sleep is disrupted, because a system that believes there's a threat present will not release you into deep rest. Hormones drift out of balance. Anxiety becomes the baseline rather than a response to anything specific.
Every one of those symptoms looks like a separate problem requiring a separate specialist. All of them are downstream of a single setting that was supposed to be temporary.
Why Would the Alarm Get Stuck?
The obvious question is why a system built to switch off wouldn't.
Part of the answer involves the upper neck, and the pathway is more direct than most people expect.
The position sensors in the small muscles at the top of your neck send signals into the vestibular nucleus and the cerebellum. Those pathways don't stop there. They have projections that continue upward into the limbic system — reaching the amygdala and the hypothalamus, the structures that set your autonomic tone.
That means the position information arriving from your upper neck helps determine whether your nervous system runs in a sympathetic state or a parasympathetic one.
Consider what that implies. If the upper neck is misaligned and [reporting inaccurately](post-why-most-of-your-balance-comes-from-your-neck.html), the signal arriving at those structures is wrong. A brain receiving conflicting information about something as fundamental as which way is up does not relax — it interprets mismatch as a reason for vigilance. And a brain that has concluded vigilance is warranted keeps the sympathetic system switched on.
At that point the trigger isn't in the environment at all. Someone can be on a beach in Tahiti, with nothing whatsoever wrong in their circumstances, and their body is responding as though something is coming out of the trees. The alarm is not responding to the world. It's responding to a faulty signal from the top of the spine.
There is a related finding worth knowing about, from a different angle. A systematic review of 36 studies of autonomic function after concussion found measurable autonomic abnormalities in all but three of them (Pertab et al., 2018). That work concerns head injury rather than the neck specifically, so it doesn't prove the pathway I've just described. What it establishes is that an injury in this region reliably disturbs autonomic regulation — which is the phenomenon that needs explaining.
Why Does This Reframe the Symptoms?
If your fatigue, digestion, immunity, and concentration have all declined together, that pattern is informative. Those are not four unrelated conditions that happened to arrive at once. That combination is the signature of a nervous system that has not left survival mode.
And that reframes the question. Rather than treating the fatigue, the reflux, the frequent infections, and the [brain fog](condition-brain-fog.html) as four separate problems, the more useful question is what is keeping the switch in the on position — and whether the signal driving that decision is accurate.
When a structural problem in the upper neck is part of what's holding that switch, it's addressable. Correcting the input allows the brainstem to receive accurate information again, and a system that concludes it is not under threat will stand its alarm down on its own.
That won't be the entire explanation for everyone. But it's a mechanical contributor to a set of symptoms almost always treated as purely chemical or psychological, and it is very rarely examined.
Wired, Exhausted, and Getting Sick More Than You Should?
If fatigue, poor digestion, frequent illness, broken sleep, and cloudy thinking arrived together, they may not be separate problems. They may be one setting that never switched off — which is what [dysautonomia](condition-pots.html) describes.
Determining what is holding that switch on is the work we do at Cerebral. If you'd like a real evaluation, we're here.
References
- Pertab JL, Merkley TL, Cramond AJ, et al. Concussion and the autonomic nervous system: an introduction to the field and the results of a systematic review. *NeuroRehabilitation*. 2018;42(4):397–427. https://pubmed.ncbi.nlm.nih.gov/29660949/