Which neurotransmitter mediates the sympathetic response?
Correct Answer: A
Rationale: The sympathetic nervous system is responsible for our "fight or flight" response to stressful situations. Norepinephrine is the primary neurotransmitter that mediates the sympathetic response, acting on adrenergic receptors in various target tissues. It helps to increase heart rate, elevate blood pressure, dilate air passages in the lungs, and mobilize energy stores in the body to prepare for physical exertion or stress. Acetylcholine is another neurotransmitter involved in the sympathetic nervous system, but norepinephrine is the primary mediator of the fight or flight response.