Understanding the stress response
Stress is an unavoidable part of life. But learning to manage it successfully can do much to improve your mental and physical health.
That's why it helps to understand just how your body reacts to stressful situations — and why the so- called fight-or-flight response, which can be life-saving in the case of an immediate physical threat, becomes detrimental when stress is a chronic feature of daily life.
What is stress?
We all encounter stress in our lives, though we might use different examples to describe it. But whether the particular stressor you’re confronting is a sudden car crash, a loud argument, or the ache of arthritis, each potential or actual threat triggers a cascade of stress hormones that produce well-orchestrated physiological changes.
You know these sensations well. Your heart pounds. Muscles tense. Breathing quickens, and beads of sweat appear. But although the physical effects may seem simple, these reactions — collectively dubbed the "fight or flight" response — require an intricate coordination of many different body systems.
A look inside the stress response
Our response to threats begins in the brain, which receives and processes information — perhaps the sight of your boss bearing down with an ominous expression, or the sound of an explosion. Instantly, a signal from the motor cortex in the brain speeds down nerve pathways to muscles, which tense and tighten, bracing for trouble. Another signal comes from the hypothalamus, a portion of the brain perched above the brainstem. It relays the warning to the nearby pituitary gland, which sends a chemical messenger via the bloodstream to the adrenal glands. In response, the adrenal glands secrete a series of stress hormones, including epinephrine, better known as adrenaline. (You’re probablyfamiliar with the so-called "adrenaline rush" that helps rev up your body. This is part of the stress response.)
The stress response
Collectively, the hypothalamus, pituitary gland, and adrenal glands make up the HPA axis, which plays a pivotal role in triggering the stress response. The hypothalamus sends a chemical messenger (corticotropin- releasing factor, or CRF) to the nearby pituitary gland, which then releases its own chemical messenger (adrenocorticotropic hormone, or ACTH) into the bloodstream (A). ACTH travels to the adrenal glands, which respond by releasing a number of stress hormones into the bloodstream (B).
At the same time, the sympathetic nervous system releases stress hormones, too (not shown). The combined effects of these hormones are widespread, as this illustration reveals. Senses become sharper, muscles tighten, the heart beats faster, blood pressure rises, and breathing quickens. All of this prepares you to fight or flee in the face of danger.
Simultaneously, the hypothalamus fires up the autonomic nervous system. This network of nerves relays the warning down through the spinal cord and from there to nerves throughout the body. In response, nerve endings in organs, blood vessels, the skin, and even sweat glands release epinephrine and norepinephrine.
This tandem surge of hormones primes your body to react to the imminent threat. In the case of an immediate physical danger, such as the sudden appearance of a prowling wild animal or an armed enemy, you respond by either preparing to stand your ground and fight, or else fleeing to safety. Either way, you need to gear up for action, which is precisely what stress hormones enable you to do.
Your breath quickens as your body takes in extra oxygen to help fuel your muscles. Likewise, energy- boosting glucose and fats are released from storage sites into your bloodstream. Sharpened senses, such as sight and hearing, make you more alert.
Your heart pounds — beating up to two to three times as quickly as normal — and your blood pressure rises. Certain blood vessels constrict, which helps direct blood flow to your muscles and brain and away from your skin and other organs.
Blood cells called platelets become stickier, so clots can form more easily to minimize bleeding from potential injuries. Immune system activity picks up. Your muscles — even the tiny hair-raising muscles beneath your skin — tighten, preparing you to spring into action.
Body systems not needed for the immediate emergency are suppressed in order to focus energy whereit’s needed. The stomach and intestines cease operations. Sexual arousal lessens. Repair and growth ofbody tissues slows.
Defusing the stress response
The autonomic nervous system, it turns out, is divided into two parts with opposite effects. The sympathetic nervous system revs up the body in response to perceived dangers, as described above. Its counterpart, the parasympathetic nervous system, calms the body after the danger has passed. But intoday’s society, stressors often pile up one after another in a combination of traffic jams, deadlines,money woes, and a host of other challenges that fill our days, rather than passing rapidly, like the wild animal that eventually lumbers away. As a result, the sympathetic system often remains engaged long after it should have yielded to the soothing influence of the parasympathetic system. The results can be damaging in many ways.
When your body repeatedly experiences the stress response, or when arousal following a terrible trauma is never fully switched off, your body’s stress response can be described as maladaptive, orunhealthy. In this situation, the stress response kicks in sooner or more frequently than normal, increasing the burden your body must handle. Maladaptive stress responses can lead to worrisome health problems. A prime example of this is high blood pressure, or hypertension, which is a major risk factor for coronary artery disease. Another is suppression of the immune system, which increases susceptibility to colds and other common illnesses.
Even faced with chronic stress, however, you can benefit from stress management techniques. Regular use of these techniques can help you tamp down the sympathetic nervous system when it is not truly needed and restore balance.
Content provided by Harvard Health Publications