What's more, activating the aggression system turns on the adrenocortical stress response without actual fighting--or even someone to fight. A hypothetical picture emerges: First, as has long been known, a signal from the nervous system (via pituitary hormone ACTH) signals the adrenals to produce a corticosteroid response that prepares the body for an emergency response, popularly called "fight or flight." Second, in this new finding, the same corticosteroid signal also feeds back to the brain, which lowers attack thresholds and facilitates fighting. Fighting, itself a stressor, then further activates the stress response. And so it goes.