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128 EFFECTS OF EARLY MALTREATMENT AND STRESSmeasurement of one component of the stress-emotion system noninvasivelythrough sampling saliva, significant advances are being made in translating theimport of the animal work to our understanding of human children and adolescents.In this chapter, I will briefly outline the current state of our knowledge andrecent attempts to merge this work with preventive intervention study designs.The Neurobiology and Neuroendocrinologyof the Stress-Emotion SystemThe neuroendocrine component of the emotion-stress system focuses on centers deepin the brain, in the hypothalamus and brainstem (Habib, Gold, & Chrousos, 2001).In an area of the hypothalamus called the paraventricular region lie cells that secretecorticotrophin-releasing hormone (sometimes referred to as CRH and sometimesCRF) and arginine vasopressin (AVP; see figure 6-1). These neuropeptidestravel through a small vascular system to the anterior part of the pituitary gland wherethey stimulate the production and release of adrenocorticotropic hormone (ACTH).ACTH, in turn, is released into general circulation and is carried through the bloodto the cortex (outer part) of the adrenal glands. In the adrenal cortex, ACTH triggersthe production and release of glucocorticoids, critical stress hormones (note:cortisol in humans and corticosterone in rats). This whole system is called the HPAaxis for its three components: hypothalamus-pituitary-adrenal cortex.In a region of the brainstem called the locus coeruleus (LC) lie the cell bodiesof the brain’s norepinephrine (NE) system, the neurotransmitter system that isintimately involved in regulating vigilance and fear behavior (see figure 6-1, panelA). Also in the brainstem are regions that regulate the sympathetic and parasympatheticarms of the autonomic nervous system. The sympathetic nervous systemincludes a direct connection between brainstem nuclei and the inner part of theadrenal glands (the medulla) that secretes epinephrine (also called adrenaline) aspart of the fight/flight response. This system is called SAM, standing for sympathetic-adrenalmedullary system. Both glucocorticoids produced by the HPA systemand adrenaline produced by the SAM system mobilize the body for actionthrough liberating energy stores. Adrenaline also increases heart rate and bloodpressure and orchestrates where blood is shunted, to muscles and brain over thereproductive and digestive systems. Glucocorticoids, in contrast, serve a wide rangeof additional functions beyond energy mobilization, which I will return to in amoment. The SAM system is a subcomponent of the sympathetic arm of the autonomicnervous system. The other arm of the autonomic nervous system, theparasympathetic arm, also plays a role in the stress-emotion system through reversingthe effects of increased SAM activity and providing input to emotionorganizingregions in the brain (e.g., the amygdala; see below) that reduce reactivityto threat stimuli (see Porges, 1995b).