Final answer:
The fight or flight response is triggered by the sympathetic nervous system. When faced with a perceived threat, the sympathetic nervous system prepares the body for action.
Step-by-step explanation:
The fight or flight response is triggered by the sympathetic nervous system. When faced with a perceived threat, the sympathetic nervous system prepares the body for action by increasing heart rate, dilating pupils, increasing breathing rate, and activating the release of adrenaline. These physiological changes help the individual either fight off the threat or flee from it.