How does stress affect my nervous system?

Created on: July 26, 2021

Maybe you have too many deadlines piling up at work. Perhaps your relationship with a loved one is not in the best place. Or like a lot of us, there’s a lot of uncertainty in your life right now. Sometimes we find ourselves getting caught up in the details, and this can stress us out. You may know that chronic stress is a big risk factor for heart disease, obesity, and depression. But how exactly does stress interact with our nervous system to enact changes in our body?

How does our nervous system work?

The nervous system can be divided into 2 parts: the central nervous system (CNS), and the peripheral nervous system (PNS). The CNS is what controls most functions in our body and mind. It consists of the brain, the spinal cord, and neurons. The PNS, on the other hand, is responsible for connecting the CNS to the rest of the body.

The autonomic nervous system (ANS) is part of the PNS. It’s a control system that manages involuntary processes like heart rate, blood pressure, respiration, and digestion. The ANS has two distinct divisions—the sympathetic nervous system (SNS) and the parasympathetic nervous system (PNS)—each with a unique role in regulating our stress and ensuring our survival.

What does the SNS do?

The sympathetic nervous system (SNS) is responsible for the fight or flight response, a physiological reaction that occurs when we are in the presence of something dangerous. When the flight or fight response is triggered, the SNS signals the adrenal glands to release stress hormones such as adrenaline and cortisol, which cause the following changes in your body:

  • Elevated heart rate
  • Elevated respiration rate dilation in your blood vessels in the arm and legs
  • Elevated glucose levels in the bloodstream

These changes give us increased strength, speed, and alertness, which allow us to deal with the emergency. While this was definitely useful for our prehistoric ancestors when being chased by a sabre-toothed tiger, most of us don’t really require it nowadays.

Here’s the problem: Your SNS triggers a similar fight or flight response whenever you’re stressed out, even though the world is much safer than in prehistoric times. The SNS doesn’t distinguish between stress caused by a meat-eating predator and stress caused by a deadline at work. This leads to conditions such as chronic stress, which is when you’re constantly experiencing the fight or flight response.

What are the effects of chronic stress on my body?

Chronic stress can seriously damage your health if you just leave it to the sidelines. It can have the following effects:

Suppressed immune system

Cortisol reduces inflammation in your body, which actually weakens your immune system. This makes you more susceptible to illnesses. In particular, chronic stress causes gut inflammation and changes the movement patterns in your colon, which decreases health-promoting bacteria like lactobacillus, allowing bad bacteria and yeast to overgrow.

Damage to both male and female reproductive systems

Chronic stress affects the production of hormones such as testosterone and estrogen. In both males and females, it can lead to difficulties in conceiving; in females, stress affects menstruation, which can lead to absent or irregular menstrual cycles.

Elevated risk of heart attack and stroke

The elevation of blood sugar levels leads to inflammation of artery walls, which causes the build-up of plaque, blocking your arteries.

This is why it’s so important to counter the effects of chronic stress, which is where the PNS comes in.

What does the PNS do?

The parasympathetic nervous system (PNS) is known as the rest and digest response. It undoes the effects of the SNS, as it lowers heart rate and blood pressure, stimulates digestion, and helps cells regenerate effectively. Because of this, rest and digest is the state you want to be in most of the time.
There is a range of techniques you can use to stimulate your PNS, which can help you combat the effects of chronic stress.

How do I get into rest and digest mode?


Breathing exercises greatly reduce stress and anxiety. Studies show that even a single breathing exercise session can reduce blood pressure, boost oxygen levels, and increase heart rate variability—all signs of a healthy PNS response.

Try The Box Breathing Method, a simple relaxation technique to shift gears from fight or flight, to rest and digest. Here’s how:

  1. Find a comfortable place to sit. Close your eyes and take a few moments to focus on your breath.
  2. Inhale slowly for four counts, and feel the air enter your lungs.
  3. Hold your breath for four counts, and feel the air enter your lungs.
  4. Exhale slowly for four counts.
  5. Repeat for a few rounds, ideally for five minutes or more, until you feel calmer and more centred.


Mindfulness is a Buddhist meditation technique that cultivates your ability to be present, attentive, and aware. It has many stress-busting benefits as it reduces cortisol, the SNS’ main stress hormone.

How to practice mindfulness:

  1. Sit in a comfortable position, either on a chair or cross-legged. Make sure your spine is straight and your shoulders are rolled back.
  2. Rest your hands on your lap, with palms facing up or down.
  3. Begin to notice the breath and the sensations in your body.
  4. If you notice your mind wandering, gentle recognize that you’re in thought and bring your attention back to your breath or the sensations in your body.

Forest bathing

Basically, get into the great outdoors as much as you can. As wacky as it sounds, studies show a big physiological impact of being among lots of trees, including lower levels of cortisol (the stress hormone), a decrease in blood pressure, and improved immune function.


Consider this your excuse to sing loudly in the shower. The simple act of singing stimulates a complex of nerves at the back of your throat, which connect to the vagus nerve. This long, critical nerve runs from your brain all the way down into your major organs and triggers the PNS or rest and digest response.

Take it slow

With the fast-paced nature of modern life, it’s easy to lose yourself in a constant state of stress and anxiety. However, with consistent effort – scheduling in your breathing and mindfulness sessions, for example – you can manage your stress and take on life feeling lighter and brighter. Remember to take a breather.