Final answer:
The sympathetic nervous system division of the autonomic nervous system is responsible for activating the 'fight or flight' response, preparing the body to respond to stressful situations with increased heart rate and other physiological changes.
Step-by-step explanation:
The autonomic nerves that speed you up during the "fight or flight" response are part of the sympathetic nervous system division of the autonomic nervous system. When you face a stressful situation, the sympathetic nerves activate various physiological changes in your body.
These include an increase in heart rate, dilation of the bronchi in the lungs, activation of sweat glands, pupil dilation, elevated blood pressure, and increased blood flow to skeletal muscles. All these changes are designed to prepare your body to either confront the threat or escape from it as quickly as possible.