results in a physiological response involving almost all bodily organs. The mind and body
interact as one, affecting each other, with a bi-directional message system (neurochemical messengers) that communicates between brain and body. Stress involves complex interactions among these systems, with the stressor first interpreted by the mind/brain as a danger, thus activating the stress mechanism. This response is based first on the individual's memories, prior decisions, beliefs, and future expectations. It will include physical, mental, emotional, and possibly spiritual response to the stressor.
If the stressor, whether real or imagined, is perceived by the person to be a threat, then a stress cascade occurs. A complex series of internal, chemical, neurologic, and hormonal changes occur automatically (Hans Selye's General Adaptation Model). The stress cascade includes:
- Neuroelectrical, neurohormonal, and biochemical responses.
- Stimulation of hypothalamus that then stimulates the pituitary gland, sympathetic nervous system, parasympathetic nervous system, adrenal glands, and pancreas.
- Whole body reaction and individual perception.
- Action: Fight or flight, followed by after-action response.
- Resolution of stress.
The brain responds to the stressor by releasing hormones into the body. Steroid hormones, primarily glucocorticoids, including the primary stress hormone, cortisol, prepare the body (heart, lungs, circulation, metabolism, immune system, skin) to deal with the stressor. Catecholamines, also called neurotransmitters or chemical messengers, are released, and these include dopamine, norepinephrine, and epinephrine. Catecholamines trigger an emotional response to the stressor (usually fear). Catecholamines also suppress short-term memory, concentration, and rational thought so that the person can act quickly. Neurotransmitters message another area in the brain (hippocampus) to store the emotional memory. Functions of the heart, lungs, circulation, immune system, mouth, throat, skin, and metabolism are all altered.
The stress organs are the hypothalamus, pituitary gland, adrenal glands, thyroid, thymus, and reproductive organs. They communicate through hormones. The adrenal cortical hormones include the stress hormones, adrenalin and cortisol, that prepare the person to face the threat. Adrenalin turns on the inflammatory system, defensive systems, and immune systems to prepare for possible injury. Cortisol stimulates the anti-inflammatory mechanism. These hormones affect sugar metabolism, blood clotting, cholesterol manufacturing, renal function, blood flow, and cardiovascular function.
If the stress response occurs on a frequent or chronic basis, it can contribute to a number of physical symptoms and illnesses. Repeated release of stress hormones causes hyperactivity in certain brain areas (hypothalamus-pituitary-adrenal axis and disrupts normal levels of serotonin, a neurochemical critical to a sense of well-being. Adaptation to stress is associated with depression and anxiety.
Stress is related to a number of chronic illnesses including heart disease, stroke, reduced immune system (increased colds, viruses), gastrointestinal problems, eating problems, diabetes, pain, sleep disturbances, sexual and reproductive dysfunction, memory problems, allergies, skin disorders, unexplained hair loss, increased periodontal disease, substance abuse, anxiety disorders, depression, and posttraumatic stress disorder.
Also see Brain Effects .