The Biology of Stress: It’s not Just in Your Head

By November 5, 2016Featured, Health, Stress, Work

Expert Article by:

Amanda Gooding, PhD

Clinical Neuropsychologist

Columbia University Medical Center

Feeling jittery while public speaking?  Notice your heart racing during an important meeting?  Feeling your stomach aching in anticipation of a big exam or deadline?  Although uncomfortable, these are common physiological reactions to stress.  That’s right – stress isn’t just in our head, it impacts our bodily functions as well.  This is because our bodies are equipped with an innate system that sets off a cascade of events in our body and our brain.  Biologist often refer to this as the “fight or flight” response, and for early humans it was especially important for protecting us from perceived attack, harm or threat to our survival (think saber tooth tigers and other vicious predators).  In today’s modern world, the threats to our survival have changed, and while we no longer regularly deal with issues pertaining to physical safety, we do have to worry about things like financial stability, housing, and planning for our futures.  While this certainly sounds like an upgrade from pre-historic times, evolution hasn’t quite been able to catch up with our increasing need to deal with prolonged stressors.

Enter the Autonomic Nervous System (ANS) – an innate system responsible for controlling bodily processes that are outside of our conscious control (i.e., regulating our heart rate, blood pressure, and breathing) while simultaneously suppressing the digestive, reproductive, and immune systems.  In short, the ANS helps the body to pour its resources into action, rather than wasting valuable energy on activities that might not be imminently necessary, like digestion and ovulation – a skill that is particularly important when dealing with potentially stressful or dangerous situations.

To break this down further, the stress response is controlled by the hypothalamic−pituitary−adrenal (HPA) axis (illustrated in the figure above). During this reaction, the hypothalamus (a brain structure involved in regulating basic body functions, like stress, sleep, sex, body temperature, and hunger) perceives a stressful stimulus from the outside world, and releases a hormone called corticotrophin−releasing hormone (CRH). This hormone signals the nearby pituitary gland to release adrenocorticotropic hormone (ACTH), which travels through the bloodstream to the adrenal glands (located on top of our kidneys).  ACTH then simulates the adrenals to release the two major stress hormones, adrenaline and cortisol, which work together to prepare the body for reaction during the fight or flight response. The main function of adrenaline is to increase heart rate and blood pressure, which allows the body kick into high gear almost instantaneously.  By contrast, the effects of cortisol are observed over the longer term – not only by increasing blood pressure, but also by increasing blood sugar and mobilizing fat and protein stores to help replenish lost energy gradually over time.

After an individual has fought or fled a stressful situation, the body should theoretically return to normal, and this stress mechanism should subside. However, during times of prolonged stress (which we often face in our daily lives) this system continues to work in over-drive, leading to exhaustion. While modern−day stressors are admittedly different from the physical threats our bodies evolved to handle, we shouldn’t discount the effects of long−term psychological stressors on our physical well−being.  For instance, over-production of these stress hormones has been found to directly contribute to poor sleep, weight gain, higher rates of heart disease, and decreased libido and fertility.  Stress can even have adverse effects on our immune system by depleting the body’s natural mechanisms of fighting off infection.

Given the intense and perpetual stressors we are likely to encounter on a regular basis, it is especially important for humans to learn and employ coping strategies to better manage stress.  Doing so will not only make for a healthier mind, but also a healthier body.  So next time you notice your heart racing or your stomach aching, don’t just ignore it – try using some deep breathing or relaxation skills!