Hypothalamus, Pituitary and Adrenal Gland Axis (HPA)

This system regulates cortisol secretion from the adrenal gland in response to prolonged stress through a series of activations of these three structures. Repeated activation of the HPA axis in response to chronic stress leads to its dysfunction (e.g. the resistance and exhaustion phase of the General Adaptation Syndrome).

Reference:
Bear, M.F., Connors, B.W. & Paradiso, M.A. (2001). Neuroscience: Exploring the Brain. (2nd Edition). Baltimore, MD: Lippincott Williams & Wilkins