hypothalamus

The ventral part of the diencephalon that forms the floor and part of the lateral wall of the third ventricle. Anatomically, it includes the preoptic area, optic tract, optic chiasm, mammillary bodies, tuber cinereum, infundibulum, and neurohypophysis, but for physiological purposes the neurohypophysis is considered a distinct structure. The hypothalamus may be divided into five regions or areas (area hypothalamica rostralis, area hypothalamica dorsalis, area hypothalamica intermedia, area hypothalamica lateralis and area hypothalamica posterior) or into three longitudinal zones (periventricular zone, medial zone, and lateral zone). The hypothalamic nuclei constitute that part of the corticodiencephalic mechanism that activates, controls and integrates the peripheral autonomic mechanisms, endocrine activity, and many somatic functions, e.g., a general regulation of water balance, body temperature, sleep, and food intake, and the development of secondary sex characteristics. The hypothalamus secretes vasopressin and oxytocin, which are stored in the pituitary, as well as many releasing factors (hypophysiotropic hormones), by means of which it exerts control over functions of the adenohypophysis.