HPA axis

The hypothalamic-pituitary-adrenal (HPA) axis refers to one of our most crucial stress response systems. When faced with a stressful situation the hypothalamus releases corticotropin-releasing hormone (CRH) which triggers the pituitary gland to release adrenocorticotropic hormone (ACTH) which triggers the adrenal cortex to release cortisol. Once a certain concentration of cortisol is achieved in response to the stressor, the hypothalamus stops producing CRH and the HPA axis stress response is “turned off”. In addition to present stressful situations, the HPA axis can be activated by something associated with a past stressful situation. This stress response system differs from that of the sympathetic nervous system ‘fight or flight’ response, as it is slower to activate and remains activated over a longer period; however, the two systems do show considerable overlap. Ulrich-Lai, Y.M. and Herman, J.P., 2009. Neural regulation of endocrine and autonomic stress responses. Nature reviews neuroscience, 10(6), p.397. Alschuler, L. (2016). The HPA Axis. [online] Integrative Therapeutics. Available at: https://www.integrativepro.com/Resources/Integrative-Blog/2016/The-HPA-Axis [Accessed 15 Nov. 2018]. Stephens, A. and Wand, G. (2012). Stress and the HPA axis: role of glucocorticoids in alcohol dependence. Alcohol research : current reviews, 34(4), 468-83.