WTF is the Autonomic Nervous System

Autonomic Nervous System: What is it, what are its two branches and why is it linked to stress?

WHAT

Your Autonomic Nervous System (ANS) is responsible for involuntary bodily functions such as heart rate, respiratory rate, and digestion, among others. It operates largely unconsciously, although it can be influenced by conscious factors.

The ANS has two branches that typically work in opposition to each other: the Sympathetic Nervous System (SNS) and the Parasympathetic Nervous System (PNS).

The SNS is more commonly known as the "fight or flight" system, while the PNS is known as the "rest and digest" system.

When we are stressed, our SNS becomes dominant, preparing the body for immediate action by increasing heart rate, respiratory rate, and diverting blood flow to muscles.

When we are relaxed, the SNS subsides, and the PNS becomes more active, promoting calming effects such as slowing the heart rate, decreasing respiratory rate, and enhancing digestion.

HOW

When we experience a stressor—psychological or physical—our SNS is triggered and takes over from the PNS.

When this happens, adrenaline and cortisol are secreted into the body as part of the stress response.

Adrenaline plays a role in preparing your body to respond to the stressor by increasing heart rate, blood pressure, and expanding airways. This helps glucose get to your muscles and brain so you can take action.

Cortisol suppresses non-essential bodily functions during a stress response in the short term so that body resources can be focused on responding to the stressor. It also plays a vital role in communicating to the brain (via the HPA axis) when the stressor has subsided.

Consistently increased levels of these hormones can negatively impact health by decreasing sleep quality, increasing cardiovascular wear, and increasing susceptibility to anxiety and depression.

WHAT TO DO

It's important to note that the stress response system is crucial for human survival. The aim is not to eliminate stress responses but to limit the number of triggers.

It is perfectly normal for a survival event, such as seeing a speeding car hurtling toward you, to trigger your stress response system.

However, many stress triggers are avoidable, such as alcohol, social media, smoking, high-sugar foods, and workplace anxiety.

If we exhibit a non-survival stress response, the aim should be to quiet our SNS to allow our PNS to take over, returning the body to a state of calm.

Strategies for doing so can include breathwork (psychological sigh), meditation, a walk in nature, exercise, or a mindful activity that requires focus outside of the stressor (for example, painting).

The purpose of these activities, beyond their intrinsic enjoyment, is to influence our biology to allow the PNS to ascend and take over from the SNS, resulting in the subsidence of the stress response.

DISC

There are many events that can trigger a stress response. Stress is not inherently "good" or "bad"; it depends on the context.

If you feel you are consistently stressed, try to investigate what could be triggering your SNS.

If you have tried lifestyle strategies for addressing your stress and they are ineffective, speak with a medical professional who will be able to suggest more comprehensive strategies.

PLEASE NOTE

At the time of sending this information was accurate to the best of my knowledge. However, by its very nature, the science on the subjects I discuss is ever evolving.

Therefore, it's important to recognise that the information I share should not be taken as medical advice and I am not medically qualified.

You should always research independently or consult a medical professional before making any changes to your lifestyle, including on the subject discussed here.

Sources for this installment of Marginal Steps:

​(Daniela et al., 2022)​

​(Ziegler, 2004)​

​(Siegel & Watanabe, 2021)​

​(Abboud & Singh, 2017)​

​(Siegel & Watanabe, 2021)​