What brain structures rouse us from inactivity and set in motion our defense mechanisms when a stressor is perceived? Predictably, the brain’s older and more primordial area, the so-called animal brain, where the hypothalamus, the amygdala, the hippocampus, the septum area, the basal ganglia and the thalamus are located. These structures, collectively called the limbic system, are interconnected and work together to initiate motor and other functional activities of the brain that mobilize the body. In this post about stress hardware, we discuss the hippocampus.
Virtually any experience perceived by the five senses appears to cause the activation of at least some part of the hippocampus. The hippocampus in turn redistributes these sensory signals to the thalamus, the hypothalamus, and other parts of the limbic system. Thus, the hippocampus acts as an important switching center through which incoming sensory signals are retransmitted and initiate behavioral reactions for different purposes. Its importance has been demonstrated empirically: experimental artificial stimulation of the hippocampus can induce a wide variety of behavioral patterns such as pleasure, rage, passivity, or excessive sexual drive.
The cells of the hippocampus appear to be especially sensitive to the effects of various stressors. Although not directly involved in the stress response, its ventral regions appear to exercise a regulatory influence on the hypothalamic-pituitary-adrenal (HPA) axis activity and are also a primary target for elevated glucocorticoid levels. The glucocorticoid hormones owe their name to their important effects on blood glucose concentration, which is the principal source of energy of the human cell. They also regulate protein and fat consumption, and the utilization of carbohydrates to produce additional quantities of energy. Cortisol is the principal glucocorticoid. Read more