Epinephrine and norepinephrine cause breathing, blood pressure, and heart rate to increase. They may also signal a feeling of fear, stimulating the senses to prepare for an attack. These hormones activate as part of the sympathetic nervous system responsible for protection by either fleeing or physical response. Essentially, the sympathetic nervous system is like the gas pedal of the car, and the hormones from the adrenal glands are the fuel.

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