Which part of the nervous system is responsible for the fight-or-flight response?

The sympathetic nervous system is a division of the autonomic nervous system that activates the body during stress or danger. It raises heart rate, increases breathing, dilates pupils, and redirects blood toward muscles. It works alongside the adrenal glands to help the body respond rapidly to threats. Its opposite is the parasympathetic nervous system, which helps calm the body and restore energy. Together, they maintain balance in the body’s automatic functions.