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The hypothalamus is stimulated to release corticotropin-releasing hormone (CRH) in response to physical or emotional stress.
CRH travels through blood vessels to stimulate the pituitary gland, where adrenocorticotropic hormone (ACTH) is then released.
In response to ACTH, cortisol (a glucocorticoid), is produced and released by the adrenal gland(s). Cortisol has multiple effects within the body. For instance, related to metabolism, it promotes the formation of usable carbohydrates from protein and lipids - in order to help the body cope with an acute stressor. The immune system is another example where function is altered under acute stress.
Cortisol then feeds back at the level of the pituitary gland, hypothalamus and hippocampus (another area of the brain with a significant number of glucocorticoid receptors). This negative feedback acts to suppress the activity of the HPA axis.
When the HPA axis functions appropriately, negative feedback will shut down the stress cascade following its necessary activation in response to stress. Overall wear and tear on various body systems from stressors can in part be limited when the HPA axis is able to function appropriately and effectively and is not overused.
Sources Consulted
Sources Consulted
Dubuc, B. (n.d.-g). Serotonin and other molecules involved in depression. The Brain from Top to Bottom. https://thebrain.mcgill.ca/flash/i/i_08/i_08_m/i_08_m_dep/i_08_m_dep_lithium.html
Grace, C. E., Kim, S., & Rogers, J. M. (2011). Maternal influences on epigenetic programming of the developing hypothalamic-pituitary-adrenal axis. Birth Defects Research Part A: Clinical and Molecular Teratology, 91(8), 797-805. https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1083&context=usepapapers
McEwen, B. S. (2005). Stressed or stressed out: What is the difference? Journal of Psychiatry and Neuroscience, 30(4), 315-318.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1197275/
McEwen, B. S., & Gianaros, P. J. (2011). Stress- and allostasis-induced brain plasticity. Annual Review of Medicine, 62, 431-445. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4251716/
Moisiadis, V. G., & Matthews, S. G. (2014a). Glucocorticoids and fetal programming part 1: Outcomes. Nature Reviews. Endocrinology, 10(7), 391-402.
http://doi.org/10.1038/nrendo.2014.73
Smith, S. M., & Vale, W. W. (2006). The role of the hypothalamic-pituitary-adrenal axis in neuroendocrine responses to stress. Dialogues in Clinical Neuroscience, 8(4), 383-395.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3181830/pdf/DialoguesClinNeurosci-8-383.pdf
