Doris’s heart suddenly races as a speeding car nearly collides with hers on the highway. which neurotransmitter is playing a role in this response?

Is the Norepinephrine, or noradrenaline. This is a neurotransmitter but it can also be called of stress hormone. This is the neurotransmitter responsible for the "flight or fight response". When we are faced with anything that's dangerous or scary, as it was with Doris, our body responds working faster because of this neurotransmitter: heart rate inscreases, as happened with Doris, breathing rate increases, pupils dilate, blood flow to skeleton muscles increases, and others...