Cherie is walking to her car late at night and notices a man following her. Cherie feels threatened and her heart rate and breathing speed up due to a release of __________ stimulating her __________.

Feeling threatened activates the sympathetic nervous system, producing the fight-or-flight response. Norepinephrine helps increase heart rate and breathing during this response, so the correct choice is “norepinephrine . . . fight-or-flight response.” Serotonin and GABA are not the signals that produce this immediate stress response.

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