The sympathetic nervous system was thought to have evolved with jawed vertebrates. But lampreys—jawless, parasitic fish that suck out the blood of their hosts—have a simple one, per recent research.

Salk Institute scientists discovered a relationship between killer T cell exhaustion and the body’s sympathetic—“fight-or-flight”—stress response. The research showed that beta-blockers could inhibit ...

Cowritten by Sarah Sperber and Tchiki Davis. The fight or flight response is the perception of danger sets off an automatic response system, known as the fight-or-flight response that is activated ...