Getting to know your autonomic nervous system: how the body fights and flees.

Since we humans in many ways are a product of evolution, one of the main jobs for our bodies and brains over the past million years or so has been to ensure our survival. Part of this has entailed developing a highly effective system that allows us to, say, run from lions or fight against (less intimidating) enemies. In these attempts we have to hand it to evolution to having been fairly successful; developing the part of the autonomic (involuntary) nervous system called the sympathetic nervous system (also called our fight-or-flight-system), which is backed up by the parasympathetic nervous system that on the other hand is responsible for our recovery, relaxation and basically taking it chill once the danger is gone. With these two being part of the autonomic system, they’re usually systems we don’t control voluntarily, but rather ones that switch on and off, and swing between the one and the other, all adapted to what our internal and external circumstances look like. When in sympathetic activation our heart rate increases, breath becomes shallower and faster, the muscles tense and we become hyper aware of what’s going on around us. And on the contrary, parasympathetic activation allows the muscles to relax, heart rate to slow, breath to become deeper and slower, and the body to attend to its repairing functions such as memory retention, the immune and digestive systems. Basically the things that will get us ready for the next time we may need to fight or flight.

Somewhat simplified it goes something like this: Danger appears, sympathetic activation switches on. Danger subsides, parasympathetic activation switches on. We run when lions are present and we rest when lions are absent. So far so good.

Enter: the evolved human brain. Here comes trouble. In numerous ways:

1.     One thing to remember about the brain is that while being a killer at solving advanced, abstract problems, it’s unfortunately less than perfect when it comes to differing between dangers that are real and dangers that are imagined. Hence, both a real lion running towards us and an imagined lion running towards us will activate the sympathetic nervous system. This causes a bit of problem since we’ve developed a language that allows us to imagine all kinds of hypothetical situations whilst being in a context that from the outside looks perfectly fine and safe (e.g. lying in bed and suddenly go into a string oframbling thoughts such as “what if my boss doesn’t like the work I do”, “what if I don’t fall asleep, I’ll be so tired tomorrow, I won’t be able to work”, “why haven’t my partner called yet, what if he was in a car accident, what if he’s dead?!”). And regardless of your cozy pillows, safe neighbourhood and a bedroom with the perfectly adjusted temperature, these thoughts are very likely to trigger your body into sympathetic activation. The brain just isn’t all that good at knowing when danger is real and when it’s imagined. 

2.     Social exclusion is considered a real danger. Even though it may not be associated with immediate danger of death to be excluded from your social sphere, there probably was a time when being left out in the cold was. Remember, our brains have in many ways far from caught up with our current society, especially when it comes to their initial reactions. Therefore any signs of social exclusion, of being disliked or dismissed are interpreted as potential dangers, triggering the sympathetic nervous system. Our perception of our social belonging fairly directly affects our bodies and our perception of the rest of the world. Researchers Zong and Leonardelli even showed in a study that the mere thought of a memory when people have felt socially excluded will influence their perception of the current room’s temperature. Being liked seems to be so important to us that it’s really hard to relax when we think we’re not. (And since the brain is crap at differing between what’s real and not, you can see how these to things in combination is a real haven for the sympathetic nervous system to run wild in).

3.     It may sound as though having a sympathetic nervous system is all bad. It’s not. Remember the lions running towards you. We should all be happy that we have an efficient system that switches on when we need to focus for an exam, jump away from a full speed car or even do something usually pleasant as, say, get married (that’s right, the sympathetic nervous system switches on just as much when the thing we need to prepare for is perceived as positive). And it’s not bad for us to be in sympathetic activation; we can for shorter periods of time manage just fine with less sleep, less food and even less frequent visits to the bathroom (sleeping, eating and pooping are pretty much all bad things to do when a car is about to hit you). The real trouble begins when we get stuck in sympathetic activation. Our bodies and brains aren’t really wired to cope with that. They’re more adapted to having a lion run towards you, but then disappearing (if you were lucky enough not to get eaten, that is), leaving you some space to relax and recover. It seems though that today we have perceived lions running towards us most all the time. Only today we call them deadlines, to-do-lists, social engagements, life goals in need of being achieved and blog posts needing to get written. The tasks never ends, and neither do our thoughts. When we get stuck in fight or flight, the body and brain will eventually start paying the price of not having the opportunity of attending to highly important functions such as memory retention, the digestive system, immune system and reproductive system. After a while it will start to show up as troubles concentrating, remembering, bowel issues and increased illness.

To sum it up: we do need our sympathetic nervous system, but it’s pretty bad for us to get stuck in it – we do need that parasympathetic part of the nervous system to keep us balanced and restored. Luckily, the concept of the autonomic nervous system being completely autonomic isn’t entirely true. There are ways of consciously switching on the parasympathetic nervous system, tapping into the relaxation response, which we’ll dig deeper into in a future blog post.