Preoptic–Periventricular Integrative Mechanisms Involved in Behavior, Fluid–Electrolyte Balance, and Pressor Responses

Body fluid homeostasis and arterial pressure are intimately related to the point that their control share many common mechanisms. The diagram shown in Figure 4.1 illustrates an interactive network (antidehydration network) activated by the dehydration of the two major body fluid compartments, extracellular [represented by the production of angiotensin II (ANG II)] and intracellular (represented by hyperosmolarity). The operation of the network involves redundancy and reciprocity and results in effector mechanisms that counteract dehydration. Although highly simplified (many important factors, e.g., aldosterone, are omitted), the network diagram suggests complex control systems orchestrated by the brain. When deranged, the operation of such systems may lead to pathologies, for example, hypertension.