The Autonomic Nervous System – Why Dog’s Don’t Get Ulcers but People Do 

 May 7, 2020

Have you ever wondered why your dog can just shake off the stress of someone knocking at your door and fall back asleep but the argument you had with your spouse keeps you up at night?

It has to do with the fact animals are instinctual and one to one with their environment.  They respond to the stress, deal with it and then return to recovery or resting state.

As humans, we have the unique feature of consciousness. We can not only assess a threat and deal with it.  We can also filter the stress, put a label on it, whether it’s accurate or not.  We can make the choice to move on or hold on.  We can decide to worry about the future and create something called anticipatory stress.  This is a subject you really want to understand and know how to implement changes in your life.

The beginning of your journey then to decode performance starts with understanding the role of the Autonomic Nervous System (ANS).

The autonomic nervous system is a network of cells that controls the body’s internal state. It regulates and supports many different internal processes, often outside of a person’s conscious awareness to maintain internal balance. Hence, it’s your external environment monitoring system, measuring and sensing what you are facing, in order to keep you in balance with your environment.

Let’s start with some basic anatomy.  Your nervous system consists of two main aspects:

  • The central nervous system: This consists of the brain and spinal cord.
  • The peripheral nervous system: This contains all the neurons outside of the central nervous system.

The ANS is part of the peripheral nervous system. It influences the activity of many different organs, including the stomach, heart, and lungs.

Within the ANS, there are two subsystems that work in opposition to help you maintain balance:

  • The sympathetic nervous system (SNS): The SNS generally prepares your body to react to something in its environment. For example, the SNS may increase heart rate to prepare you to escape from danger. It’s responsible for the classic fight, flight or fright response.  Some have used the analogy of the gas pedal.
  • The parasympathetic nervous system (PNS): Parasympathetic system mostly regulates your body functions while at rest. It’s responsible for rest, digest and restore.  The PNS is analogous to the breaks.

Your Autonomic Nervous System is concerned with the concept of homeostasis or a state of balance necessary to support health.  Allostasis is when you are out of balance and your ANS is seeking to bring you back into balance by activating one of the two branches.

Here is a partial list of what homeostasis regulates:

  • Body temperature
  • Heart rate
  • Body temperature
  • Respiration rate
  • Metabolism
  • Glucose levels
  • Digestion
  • Blood acidity levels
  • Water and electrolytes

When you face stress, your ANS prepares your body for action through the “fight or flight” response.

If the body perceives a threat in the environment, the sympathetic branch of the ANS reacts by:

  • elevating heart rate
  • expanding the airways to make breathing easier
  • releasing stored energy
  • increasing strength in the muscles
  • slowing digestion and other bodily processes that are less important for taking action

These changes prepare the body to respond appropriately to a threat in the environment. Herein lies a problem…humans are unique in how we perceive stress.  Not only do we react to real stress, we can create it in our minds.

We can activate the sympathetic branch of our ANS from work-stress, financial concerns, or relationship problems.  Our flight or fright response activated when we ruminate about the past or worry about our future.

When we activate our stress response chronically from these perceived threats it begins to do real damage to our bodies.  Chronic disease including heart disease, diabetes and hypertension are all linked to ANS imbalances.  To quote Dr. Bruce McEwen, “allodynamic adaptation has price, and the cost of this adaptation is called allostatic load – the wear and tear on the body and brain.”

How we filter stressful events and manage stress day to day has a significant impact on the “price” we pay for our stress.  The stress response is meant to be an adaptive or healthy mechanism to protect you.  When you fail to manage stress properly over the long term, this protective mechanism then turns into a maladaptive or destructive force in your life.

If your autonomic nervous system is chronically out of balance it will get in the way of you becoming an elite performer.  Imbalances in your ANS will war against concentrating your attention.  Cognitive function is lowered, preventing you from absorbing new information and applying it in novel ways.

The next piece of the puzzle in learning how to manage stress and keep your autonomic nervous system in balance is understanding the role of your brain.  This is the topic of the next Decoding Human Performance blog post.


McEwen, Bruce S., and Peter J. Gianaros. 2011. “Stress- and Allostasis-Induced Brain Plasticity.” Annual Review of Medicine 62: 431–45.

https://www.medicalnewstoday.com/articles/327450#summary What is the Autonomic Nervous System. Medically reviewed by Nancy Hammond, MD on January 10, 2020 — Written by Aaron Kandola