How Has Stress Evolved? Parasympathetic and Sympathetic Nervous System

Can you guess the #1 condition we see at Chambers Clinic? 

Hint: It’s the biggest killer in America

Is it … Heart disease? Cancer? Diabetes? Obesity? A virus run amok?

The answer is: Yes. (Trick question). Because all of these have a common denominator: chronic stress. 

The Two Nervous Systems

Though constantly evolving, our human genome has been around for more than a million years. While stress a million years ago and stress today may look wildly different, to the brain, hearing the growl of a lion near camp on the savanna and hearing the beep of an incoming email from the boss, are the exact same thing -- and elicit the same reaction.

That’s because we have two primary nervous systems hardwired into our bodies: the sympathetic – “fight or flight” nervous system – and the parasympathetic - “rest and digest”. (We also have an autonomic nervous system which automatically operates us; we don’t have to tell our hearts to beat every second or command our food to move another centimeter down the pipes – pretty cool, right?). 

Sympathetic Stress

The stress we hear about so often is that sympathetic “fight or flight” stress. When you look at our brain’s “original factory settings,” sympathetic stress used to be a good thing -- because it was rare. It exists to respond immediately to an emergency – and get us the heck out!

Adrenaline (or epinephrine) is released from the adrenal glands to sharpen the senses and increase our heart and breathing rates (more oxygen!). The hormone cortisol – also released from the adrenals -- helps to get glucose (fuel) into our muscles for an anticipated run from that lion. 

When in “fight or flight” mode, any systems we don’t need get shut off – we don’t need to process food in the stomach, pee or poop, or have sex, for example. We just need to run, run, run. When the threat was over, sympathetic mode is switched off -- and we drift back to our default “rest and digest mode”. 

Now, you’re sitting at your desk. In comes that email. Same “fight or flight” response. 

In comes a call. Your kid threw up at school. Same response.

Text from ex-partner. Same response. 

Watching TV news. Same response. 

Troll on Facebook. Same response. 

Briefly choke on water and cough; you wonder if it’s -gasp- Covid-19. Same response. 

But typically, when these stressors happen, we don’t run. We’re sitting at our desk. We’re lying in bed at night trying to get to sleep. Neither fight nor flight ever occur. We sit. We stew. We worry. We make it worse. 

And when this happens time after time, that adrenaline surge becomes chronic. Your heart rate remains elevated. You get anxious or jumpy easily. That glucose release has no running or other flight activity to burn it all off – so we store it – as fat -- sometimes in the arteries – atherosclerosis. 

Remember, when the brain remains on high alert, other functions shut off. So now you can’t sleep well. Can’t digest food well. Can’t poop well. Don’t breathe deeply. Don’t heal well from injuries. 

Parasympathetic Living

Our bodies and minds are meant to live and work more parasympathetically. But when was the last time you were truly parasympathetic? 

Think about a newborn baby. How often is he or she stressed out? Hungry. Soiled diaper. Not being held. The strange fright of opening one’s eyes on waking. These are emergencies to a new brain (and even to many not-so-new brains). Other than that, babies are generally happy, cooing, curious, observant, learning – they are parasympathetic almost all the time. 

A native human on the savannah didn’t have many emergencies either; aside from the occasional predator, distant fire or yelp from someone’s stubbed toe, we can easily imagine that they lived and worked in peace – parasympathetically. 

When emergencies are solved, the brain rewards itself with dopamine. That baby gets hungry? Emergency. She gets picked up by mom -- less emergency. Getting milk -- problem solved. Reward. Dopamine hit, relaxation. Return to parasympathetic mode. Max relax. 

Today, we are bombarded by emergencies. These cause chronic stress even on the most subtle levels. Untreated, chronic stress can lead to a variety of long-lasting health problems. We need to be back to our original factory setting. If not, we need to stop and make lifestyle changes.

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