The Autonomic Nervous System Part 1: Fight, Flight or Freeze

This week we'll be looking at parts of our nervous system, the balance between them, and how that plays into pelvic pain.

The Autonomic Nervous System

The autonomic nervous system (ANS) controls our involuntary nervous responses, like our heartbeat and digestion. We don't have to think about these functions for them to happen.

Three main parts comprise the ANS: the sympathetic, parasympathetic, and enteric. They work together to maintain homeostasis, or balance, in the body.

The Sympathetic Nervous System: Fight, Flight or Freeze

Often called the "fight or flight" response, the sympathetic nervous system is more accurately a "fight, flight, or freeze" response. Simply put, this is our defense mechanism.

If you were attacked by a hungry animal or a hostile person, you would try to fight it off. This is the "fight" response.

On the other hand, if it was possible, you may instead run, rather than staying to fight. This is the "flight" response.

You know the phrase "like a deer caught in the headlights?" That is the "freeze" response. To freeze - originating from the instinct to remain immobile in the hopes of not being noticed by a predator - is a technique used by various prey animals as well as humans. The freeze response includes playing dead. (Many predators prefer to eat live animals rather than ones that have already kicked the bucket, so instead of attacking, they may sniff around, decide said the prey was dead, and move on. Once the threat has passed,  the prey can relax and go back to living.) 

In human terms, the "freeze response" would include hiding in fear, or submitting to an attack in the hopes the attacker would leave you alone or at least reduce the severity of the attack. 

Of course, these days modern Americans are not usually being attacked by predators. So instead our sympathetic nervous is activated by other threats: a car swerving in front of you, almost being hit while crossing the street, or...stress. A looming deadline for an impossibly huge project, financial worries, family drama, dreading an exam. Daily stresses are interpreted by our nervous system as threats, and without our conscious control, create a specific response in your body.

The Sympathetic Response

What happens when your body perceives a threat? It prepares for "fight, flight or freeze." Functions that are not essential to your survival in that moment are shut down: blood is shifted from your digestive system to your muscles, your heart races, you start pumping out adrenaline, your hairs stand on end, your pupils dilate. 

In the olden times, this response would help us elude a threat. Once the threat passed, we could relax and go back to other essential functions, like digestion, or a slower, more sustainable heart rate. 

But today we have perceived threats around us all the time - rushing to get to work, your two year old having a tantrum, trying to avoid the bully at school. So our sympathetic nervous system is "on" more frequently.

But the sympathetic nervous system is supposed to help with homeostasis, remember? That's balance in the body. If our sympathetic nervous system is being called upon more frequently, we are out of balance, what we commonly refer to today as being "stressed."

Next Up

In the next segment we will learn about the sympathetic nervous system's buddy, the parasympathetic nervous system. While the sympathetic nervous system is often maligned in our society - who likes being stressed? - both are needed to maintain balance.