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. Author manuscript; available in PMC: 2014 Nov 21.
Published in final edited form as: Nat Rev Neurosci. 2009 Jun;10(6):397–409. doi: 10.1038/nrn2647

Figure 1. General scheme of brain acute stress-regulatory pathways.

Figure 1

Stressors activate brainstem and/or forebrain limbic structures. The brainstem is able to generate rapid hypothalamus-pituitary-adrenal (HPA) axis and autonomic nervous system (ANS) responses via direct projections to hypophysiotrophic neurons in the paraventricular nucleus of the hypothalamus (PVN) or to preganglionic autonomic neurons (bottom-up regulation). In contrast, forebrain limbic regions have no direct connections with the HPA axis or the ANS and thus require intervening synapses prior to accessing autonomic or neuroendocrine neurons (top-down regulation). A high proportion of these intervening neurons are located in hypothalamic nuclei that are also responsive to homeostatic status, providing a mechanism by which the descending limbic information can be modulated according to the physiological status of the animal (middle management).