The neuroendocrine system
Early during evolution, the neuroendocrinium developed as its own organ system. With its numerous intercellularand inter-organ mediators, the hormones, it fulfills important functions to synchronize and connect organs and tissues. Likewise, during stress, the neuroendocrine system, as a complex orchestra with not yet fully understood interactive mechanisms, plays one of the most important roles in the body's adaptation to harmful events, such as injury or disease.
Operational definitions (by Jacobo Wortsman, M.D.)
In general terms the endocrine system comprises hormone-producing organs (glands) that regulate the function of other organs. On functional activation, endocrine organs release their secretory products into the blood. Thus, activation can be assumed to occur when there is evidence of increased hormone concentrations in plasma.
Stress may be defined as any changes in the external or internal environment that elicit a highly organized and synchronized neuroendocrine response. Whereas changes in the internal environment can be quantified according to the degree of interference with homeostasis, changes in the external environment (psychologic stress) cannot be quantified in this manner. Thus, the description of stress must include both the nature of the stressful stimulus and the subsequent functional changes. Nevertheless, because of the universal and severe organ involvement during cardiac arrest, it can be safely assumed that this condition per se represents a stress of maximal degree, without consideration of hormone levels.
The term neuroendocrine response, as used in the description of endocrine reactions to stress, emphasizes the regulatory control placed by the hypothalamus over the entire endocrine system.