ABSTRACT
The sympathetic adrenal–medullary (SAM) system and the hypothalamus–pituitary–adrenal (HPA) axis are the main neuroendocrine systems initiating and organizing the responses needed for the fight-or-flight reaction (Cannon, 1915). An essential feature of this fight-or-flight response is that it prepares the organism for situations demanding high energy expenditure. This stress response is triggered by the hypothalamus mainly through the sympathetic nervous system (SNS) and maintained by the activity of the above neuroendocrine systems in every situation involving physical effort. They coordinate the response of many other physiological systems to a variety of stressors, including the immune and cardiovascular systems, as well as energy production and utilization and, ultimately, also behaviour.
