Understanding the Physiology of Stress
What is stress?
Stress, put simply, is our body's reaction to feeling under threat or pressure. For our ancestors, stress responses would occur to deal with daily life-threatening situations such as famine, predators or tribe wars; today it’s more likely the struggles to pay rent or bills. A certain level of stress is normal; it’s what makes us human. But it’s much rarer today that we’re met with truly life-threatening situations, and so our limbic system (“the part of the brain involved in our behavioural and emotional responses”) often overexaggerates the level of threat it perceives and in turn the emotional arousal it fires out.
Stress at the physiological level then is emotional arousal, the perception of threat by our limbic system. When our limbic system perceives a threat, it quickly moves into a state of alarm, or our ‘fight or flight’ response, setting off a number of physical processes throughout the body. Within just a few milliseconds of sensing threat, an electrical impulse is sent throughout the nervous system. Within half a second, powerful ‘performance-enhancing’ chemical hormones, such as cortisol and adrenaline, are released into our bloodstream. The release of these hormones is an attempt to put our bodies in a state of peak physical performance in order to increase our chance of survival. You can see how this would have been useful for our ancestors to fight off tigers or bears, but is less helpful when we’re about to give an important presentation at work!
Physical symptoms of stress
Shortness of breath. Shallow fast breathing. The body demands more oxygen to supply the limbs with additional energy
Dry mouth. Saliva is redirected to the blood stream to help blood pump faster
High blood pressure. Racing heart rate. The heart pumps blood harder and faster to supply the limbs with additional oxygen and energy
Dizziness/Dissociation. Feeling “spaced out”. Bloody supply to the head is reduced as oxygen is diverted to the limbs. Powerful chemicals have a pharmalogical action on the brain designed to keep us at the maximum alert levels
Poor digestion. Blood and energy is redirected from the stomach to major muscles
Urination. Defecation. Vomiting. A body even one pound lighter can move faster
Sweating. Clammy hands and skin. A wet body is more slippery and therefore more difficult to catch. The body attempts to stay cool so as to preserve peak performance temperature
Visual distortion. The pupils widen to receive more information
Time distortion. The brain speeds up to receive more frames per second
Aching muscles. Shaking. The large muscle groups such as the back, shoulders, legs and arms become tense and energy-laden
Butterflies/tension in stomach. The solar plexus area contains complex nerve bundles that alert us to the presence of danger by tightening
(symptoms and descriptions taken from Anxiety Relief, 2017, pp.24-26)
Note that we don’t always experience all of the above symptoms, nor at the intensity described above, but looking at these symptoms we can begin to see why we experience some of them when stressed.
Emotional symptoms of stress
As well as physiological or physical symptoms, stress responses typically result in difficult thoughts and emotions: worry, uncertainty, fear, anger, irritability. It is then natural for our thoughts to align with these feelings, and so we think of worst-case scenarios in an attempt to protect ourselves from the perceived danger - in CBT we call these Automatic Negative Thoughts (ANTs). Becoming cynical and cautious, we start to filter out the positives, jump to conclusions, and engage in ‘all or nothing thinking’. See a full list of unhelpful thinking habits (with alternative, more realistic thoughts given for each).
The physical and emotional symptoms of stress we have highlighted are sometimes confused with burnout, so it’s worth quickly noting the difference between the two. While stress is our limbic system’s response to a perceived threat, burnout is the state of mental, emotional and physical exhaustion that is caused by the accumulation of excessive and unchecked stress over time. See a more detailed comparison of signs of stress and burnout.
Stress response types
We don’t all experience the same emotional symptoms of stress; we respond in different ways and different activities will help to alleviate our stress response:
Over-excited stress response. Associated with irritability, agitation, anger, and feeling overly emotional. In the body this response can cause muscle tension, teeth grinding, clenched fists or jaw, shallow breathing. If this sounds like you, you will respond best to activities that quiet you down, e.g., listening to soothing music, creating some artwork or doodling, aromatherapy, meditation or muscle relaxation, or easy walking in nature
Under-excited stress response. Associated with procrastination, dips in energy, productivity and motivation, dissociation, and feeling ‘spaced out’, numb or becoming withdrawn. If this sounds like you, you will respond best to activities that are stimulating and energising, e.g., running in place or doing star jumps, dancing to lively tunes, stretching, rolling your head in circles, getting outside for some fresh air or a short, brisk walk
Immobilisation stress response. Associated with freezing and inability to take action or make decisions. If this sounds like you, you will respond best to activities that reboot your nervous system and reactivate your mind and body, i.e., physical movement that engages both your arms and legs: walking, swimming, running, dancing, climbing, tai chi, yoga
Stay tuned for the next article in this mini-series: Understanding Common Causes and Ways to Manage Stress. See also our other articles on stress and self-care activities.
