Figure 134

Vasopressin. Vasopressin is synthesized by the paraventricular and supraoptic nuclei of the hypothalamus. Vasopressin is stored in the posterior pituitary gland and released in response to osmotic or volume-dependent baroreceptor stimuli, or both. Atrial filling inhibits vasopressin release. Increases in plasma osmolality increase vasopressin release; however, the relationship is shifted by the status of extracellular fluid (ECF) volume, with decreases in the ECF volume increasing the sensitivity of the relationship. Stress and trauma also increase vasopressin release [15]. Therefore, when ECF volume and blood volume are diminished, vasopressin is released to help guard against additional losses of body fluids. (Adapted from Navar [8].)

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