Pub. date: 2009 | Online Pub. Date: January 26, 2008 | DOI: 10.4135/9781412964517 | Print ISBN: 9781412909167 | Online ISBN: 9781412964517| Publisher:SAGE Publications, Inc.About this encyclopedia
Hormones act as chemical messengers throughout the body, sending signals between cells or groups of cells. These signals play a primary role in physiological processes ranging from immune function to the reproductive cycle. Hormones have also been implicated in a number of complex behaviors including sex, aggression, and performance on cognitive tasks. In humans and other mammals, the hypothalamus acts as a master control center for the release of hormones, based on input it receives from other areas of the brain. As a result, the type and amount of hormones released in the body often depend upon perceptions of the environment. In addition, most hormones, including the primary sex hormones, work within a target cell by either increasing or decreasing the activity of specific genes. Conceptually, this means that hormones do not cause behaviors but, rather, make behaviors more or less likely in response to a situation. This entry Hormones ...