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Updated 19 September 2018

What is stress?

Stress is the leading cause of many deadly illnesses.

Although stress is something we all talk about, it can be a difficult concept to understand and define. The best place to start may be to view it from a biological perspective.

Humans, like all organisms, have to interact with their environment to fulfill their needs. Stress is what happens when we’re faced with challenges in our environment. It’s important for us to experience challenges as this is how we learn and adapt to our environment, and thus stress can be healthy and natural.

An example of the beneficial aspects of stress can be seen in the effects of exercise on muscle growth. When muscle cells are stressed, such as when we exercise, they become enlarged and the muscles become stronger and better able to perform their tasks in future.

When we’re faced with a stressful situation, pathways in our body are activated to produce a stress response.

The stress response

The stress response is also called the “fight, flight or freeze” response and is initiated in the brain when we perceive a situation as threatening. In nature, a stressor could involve being faced with a predator such as a lion.

The stress response is designed to provide an individual with the best chances of getting out of a dangerous situation (e.g. escaping the lion). This response is mainly generated by the sympathetic nervous system (SNS) and the hypothalamic pituitary adrenal (HPA) axis.

The SNS and the parasympathetic nervous system (PNS) form part of the autonomic nervous system (ANS) of the body. The ANS helps keep the body in balance.

In stressful situations, the SNS prepares the body to respond to the stressor through changes such as increased heart rate, increased breathing rate, enhanced mental alertness, increased blood flow to the muscle cells, and decreased blood flow to the digestive system.

The PNS is active when the body is in a relaxed state. It helps to conserve energy and to support processes such as digestion and immune function.

The HPA axis involves a cascade of hormones, with the end result being the release of cortisol from the adrenal glands. Cortisol helps to prepare the body to deal with stress by releasing energy stores and altering the immune and inflammatory responses. The stress response essentially redirects energy and focus to the systems in the body required to survive the stressful situation, and away from other ongoing processes in the body such as growth, digestion and reproductive function.

The components of the “fight, flight or freeze” response are vital for survival. It becomes a problem, however, when these systems get activated too frequently or for too long and the body remains in an activated state during which it loses balance or homeostasis.

Stress that is severe, prolonged or frequent can have negative effects on our health. This is usually known as chronic stress.

In everyday life, we’re all faced with multiple challenges such as traffic congestion, academic or work stress, conflict in our relationships, financial problems, crime in our communities etc. This can lead to repeated activation of the stress response, which is meant to be a short-term response to help us out of a crisis situation.

Our response to stress is influenced by other factors as well, such as our thoughts and feelings about the challenges we face. For instance, if you spend your time in traffic doing something that relaxes you, such as listening to music or podcasts, then you’re less likely to become frustrated and will have less of a stress response than the person who becomes upset and angry.

Thus, the cause of stress isn’t only the challenge we’re faced with; it’s also important how we respond to it. We can therefore think of stress as being faced with challenges that are overwhelming our coping strategies.

Reviewed by Dr Leigh van den Heuvel, psychiatrist at the Faculty of Medicine and Health Sciences, Stellenbosch University and Tygerberg Hospital. August 2018.

Read more:
What causes stress?

 
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