Stress, a word generally associated with difficult experiences both emotionally and physiologically, is an internal or external signal hinting at potential threats. Understanding stress is of utmost importance because it is biologically important, enabling processes of adaptation to a constantly changing environment (Gunnar and Quevedo, 2007). Animal stress responses are comprised of the activation of neurobiological systems that help preserve viability through allostasis, an active process by which the body responds to daily events and maintains a state of equilibrium (McEwen, 2007) . There are two systems in which stress responses in mammals are affected: the sympathetic-adrenal system (SAM) and the hypothalamic-pituitary-cortical-adrenal system (HPA axis). The SAM is part of the system that releases adrenaline/epinephrine from the center of the adrenal gland. These increases in epinephrine circulation allow for rapid mobilization of metabolic resources and organization of the fight-or-flight response. In contrast, the production of glucocorticoids by the HPA axis takes time and is capable of crossing the blood-brain barrier (Gunnar & Quevedo, 2007; McEwen, 2007). But what is the method behind the HPA axis? Anatomical structures known to mediate the stress response are found in both the central nervous system and peripheral tissues. If one were to take a closer look at the HPA axis, it would be clear that the effectors of this stress response are located in the paraventricular nucleus of the hypothalamus (PVN), the anterior lobe of the pituitary gland, and the adrenal glands. . Neurons located in the PVN synthesize corticotropin-releasing factor (CRF) and vasopressin. CRF, a key neuropeptide, has been middle of paper...... stress. Journal of Psychosomatic Research, 53(4), 865-871. Vyas, A., Mitra, R., Shankaranarayana Rao, B.S. and Chattarji, S. (2002). Chronic stress induces contrasting patterns of dendritic remodeling in hippocampal and amygdaloid neurons. Neuroscience, 22(15), 6810-8. Vyas, A., Pillai, AG and Chattarji, S. (2004). Recovery from chronic stress fails to reverse amygdaloid neuronal hypertrophy and improvement in anxiety-like behavior. Neuroscience, 128, 667-673. doi:10.1016/j.neuroscience.2004.07.013Vyas, A., Jadhav, S., & Chattarji, S. (2006). Prolonged behavioral stress enhances synaptic connectivity in the basolateral amygdala. Neuroscience, 143, 387-393. Wilber, A., Walker, A., Southwood, C., Farrell, M., Lin, G., Rebec, G., et al. (2011). Chronic stress alters neuronal activity in the medial prefrontal cortex during recovery from extinction. Neuroscience, 174, 115-131.