amygdala hijack
n. An immediate, overwhelming, and usually inappropriate emotional response to a perceived threat or emergency.
Example Citations:
Psychologists call this an amygdala hijack, a point at which the most unevolved part of our brains — the amygdala — overrules every other civilised impulse and quite simply, goes nuts.
—Natalie Reilly, “Is crying at work career suicide?," Daily Life, April 3, 2013