Central autonomic regulation of stress defense response

Abstract

Stress increases cardiac function, ventilation, and body temperature and induces analgesia. These changes, which result in an increase in metabolic rate, oxygen supply, and the conduction velocity of nerve impulses, prepare the body for a fight-or-flight response and collectively called as the defense response. A part of the hypothalamus called the defense area has long been known to play a key role in these responses, but the precise mechanisms are largely unknown. Our recent findings suggest that orexin (hypocretin) neurons act as a master switch of the defense response. In addition, our results, as well as those from other researchers, suggest that orexin neurons do not regulate specific behaviors such as the fight-or-flight responses, but rather integrate the autonomic functions and behaviors in a broad sense or in a vigilance state-dependent manner. The orexin system seems to be a pivotal link in the psychosomatic interaction.