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The hypothalamic-pituitary-adrenal axis (HPA axis) is an interactive neuroendocrine unit comprising of the hypothalamus, the pituitary gland, and the adrenal glands. The hypothalamus is located in the brain and the pituitary at the base of it, whereas the adrenals are on top of the kidneys.
The HPA axis plays key roles in basal homeostasis and in the body’s response to stress. The major pathway of the axis results in the production and secretion of cortisol. The hypothalamus responds to basal neural input which follows a circadian rhythm and input as a result of stress by increasing the secretion of corticotrophin-releasing hormone (CRH) from the hypothalamus. This increase in CRH acts upon the anterior pituitary gland to secrete adrenocorticotropic hormone (ACTH), which in turn circulates to the adrenal cortex to stimulate the release of cortisol into the bloodstream. The HPA axis is an example of a negative feedback loop; cortisol can...
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