Which neurotransmitter is involved in the body’s fight or flight response and increases heart rate?

Epinephrine, also known as adrenaline, plays a crucial role in the body's fight-or-flight response. This neurotransmitter is secreted by the adrenal glands when a person perceives a threat. Its primary function in this context is to prepare the body to either confront or escape from the source of danger.

Epinephrine has several physiological effects, one of which is the increase of heart rate. This is part of a broader suite of changes that enhance physical performance and readiness during stressful situations, including the dilation of air passages in the lungs, increased blood flow to muscles, and the release of energy stores. By elevating heart rate, epinephrine ensures that more oxygen and nutrients are delivered to vital organs and muscle tissues, thereby improving the body's ability to respond quickly and effectively to perceived threats.

In contrast, other neurotransmitters listed, such as dopamine, play key roles in reward and pleasure pathways; substance P is associated with pain perception, and endorphins primarily function to alleviate pain and induce feelings of pleasure. None of these neurotransmitters directly contribute to the fight-or-flight response like epinephrine does.