APA Dictionary of Psychology

n. the sensation caused by a need for increased fluid intake to maintain an optimum balance of water and electrolytes in body tissues. Water is lost from the body mainly in urine, through sweat, and via the lungs. Dehydration causes a reduced production of saliva and the feeling of a dry mouth. In addition, a specialized area of the hypothalamus in the brain detects and responds to the changes in osmotic pressure that result from increased concentration of electrolytes in extracellular fluid subsequent to water loss (see osmoreceptor). See also hypovolemic thirst; osmometric thirst.