The Autonomic Nervous System
First Published 9th February 2022
(Last Updated 20th November 2023)
For 99% of human existence, we have spent most of our time in the natural environment. Most of our physiological functions have evolved in, and are designed for, a natural environment. It is only in the last couple of hundred years, since the Industrial Revolution, that we have become predominantly urban dwellers. However, the human race has not adapted fast enough to keep up, and many people find that urban living puts them in a permanent state of stress.
In her paper ‘The Biophilia Hypothesis and Life in the 21st Century: Increasing Mental Health or Increasing Pathology?’, Professor Eleonora Gullone writes:
“Technology has enabled us to plough and pave the most unlikely landscapes, to travel and communicate across unforeseen distances, and to technologically produce and manipulate material goods and sentient beings, including ourselves. Not only have the changes to our lifestyles been immense compared to those of our ancestors, but we go on advancing with the blind assumption that the human species has an unlimited capacity to adapt to the environment, no matter how far removed it is from that in which we evolved. But do we indeed have an unlimited capacity to adapt?”
In this article we are going to look at the concepts of ‘fight or flight’ and ‘rest and digest’ that humans have developed as evolutionary responses to their environments and how these may be viewed as maladaptions to our environment in modern times. Evidence is mounting that we are not adapting well and may have exceeded our capacity to adapt. Urban living causes us to be on constant high alert and this stress can lead to physical problems such as high blood pressure and heart disease, as well as psychological and emotional problems such as anxiety and depression.
The Role of the Autonomic Nervous System
The Autonomic Nervous System is the part of the human nervous system that is responsible for regulating involuntary physiological processes such as heart rate, blood pressure, respiration, and digestion. It comprises the Sympathetic and Parasympathetic nervous systems.
The Sympathetic Nervous System
The sympathetic nervous system directs the body's rapid involuntary response to dangerous or stressful situations. A flood of hormones boosts the body's alertness and heart rate, sending extra blood to the muscles and pumping adrenaline around the body. The sympathetic nervous system prepares the body for intense physical activity and is often referred to as the ‘Fight or Flight’ response.
The Parasympathetic Nervous System
The parasympathetic nervous system has almost the exact opposite effect and relaxes the body and inhibits or slows many high energy functions, and sometimes referred to as the ‘Rest and Digest’ response.
When we are under artificial lighting, sitting in a traffic jam, working long hours or experiencing ‘technostress’ (the negative psychological link between people and the introduction of new technologies), this constant bombardment of stimuli can activate the ‘fight or flight’ response, even though there is not a Sabre-Tooth Tiger in sight. The body often reacts to these stresses as if they are potentially life-threatening, even when they are not. This is because the sympathetic nervous system is not only triggered by physically dangerous situations (coming face-to-face with a Sabre-Tooth Tiger) but also by emotionally dangerous situations such as rush hour traffic, demanding jobs and bosses and social media.
Research suggests that Forest Bathing can positively influence the autonomic nervous system, primarily by inducing a relaxation response associated with the parasympathetic nervous system. Spending time in natural environments, especially forests, has been linked to:
Reduced Stress
Forest bathing has been shown to decrease cortisol levels (a stress hormone) and lower blood pressure. The calming and serene atmosphere of the forest can help individuals relax and reduce stress.Improved Mood
Being in nature has been associated with improved mood and reduced symptoms of anxiety and depression. The sights, sounds, and smells of the forest can have a soothing effect on the mind.Enhanced Immune Function
Some studies suggest that spending time in nature can strengthen the immune system. While the exact mechanisms are not entirely clear, exposure to phytoncides - aromatic compounds emitted by trees - may play a role in boosting the immune system.Better Sleep
Being in a natural environment may contribute to better sleep quality. The relaxation induced by forest bathing can help regulate sleep patterns and improve overall sleep quality.
When people engage in Forest Bathing, they often disconnect from technology, engage in mindful nature-connection activities, and immerse themselves fully in the sensory experiences the forest offers. This intentional immersion in nature can trigger the relaxation response, promoting a state of calmness and wellbeing.
Overall, while more research is needed to fully understand the mechanisms behind the effects of Forest bathing on the autonomic nervous system, the evidence suggests that spending time in natural environments, especially forests, can have numerous positive impacts on both mental and physical health by promoting relaxation and reducing stress.
