Stressors may be either of physiological or psychological etiology (Lavallo, 1997; Upledger, 1987). Any threat to the homeostatic mechanisms of the body is considered a stressor (Lavallo, 1997). Physical stressors are events that directly challenge one’s health, examples being: significant temperature changes, infection, toxic substances, or injuries. Psychological stressors challenge one’s well being because of how they are perceived by that individual (Lovallo, 1997; Selye, 1976). Examples of psychological stressors are great disappointment, fear, job or family related demands and so on. These stressors may be the result of an immediate event or past and future worry that manifests in one’s thoughts, resulting in a stress response that uses the same biological sympathetic responses that would prepare that individual’s body to take action (Selye, 1976).

Stress is simply a matter of how stressors are perceived, followed by the actions that the Central Nervous System (CNS) imposes on the body (Selye, 1976). It is non-specific in that it can come from any external or internal factor perceived in the CNS. The stress response is the body’s compensatory reaction due to interference that a stressor poses (Lovallo, 1997; Selye 1976).

The hypothalamus-pituitary-adrenal axis (HPA) is the homeostatic mechanism that provides living beings with a means to compensate for stressors that come from the external as well as internal environments (Chourosis, 1992). Through the actions of hormones and nerve activity, modifications are made in all of the bodies systems in order to deal with stressful changes (Lovallo, 1997). Korszun (2002) found that it is likely craniofacial pain acts as a strong activator of the HPA. This observation possibly demonstrates that stress can come from physical as well at psychological origins and vice versa. No matter the cause the body’s biological reaction to stress is essentially the same.

This is how the three glands of the HPA axis work together to produce cortisol.

Definition: The hypothalamic-pituitary-adrenal axis is a complex set of interactions between the hypothalamus (a part of the brain), the pituitary gland (also part of the brain) and the adrenal or suprarenal glands (at the top of each kidney.) The HPA axis helps regulate things such as your temperature, digestion, immune system, mood, sexuality and energy usage. It’s also a major part of the system that controls your reaction to stress, trauma and injury.

Research links fibromyalgia and chronic fatigue syndrome with abnormalities in genes involved in the HPA axis. (Primarily the hypothalamus in fibromyalgia and primarily the adrenals in chronic fatigue syndrome.)

The HPA axis also is involved in anxiety disorder, bipolar disorder, post-traumatic stress disorder, clinical depression, burnout and irritable bowel syndrome.

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