Third Level: The Hypothalamus

Abstract

The hypothalamus is a phylogenetically ancient part of the CNS, and its structure has remained relatively constant in terrestrial vertebrates throughout evolution. The hypothalamus participates as the third level of the ANS hierarchy in the coordination of specific behaviors (defense behavior, thermoregulation, feeding, sexual and maternal behavior). This Chapter discusses the hypothalamic mechanisms that control hormone secretion and how they vary during a 24-h cycle. The nature of the defense behavior, feeding behavior and temperature regulation is described.