What impact does nicotine have on heart rate?

Nicotine primarily acts as a stimulant and is known to increase heart rate. When nicotine is consumed, it stimulates the release of catecholamines, such as adrenaline, which prepares the body for a fight-or-flight response. This response results in an increased heart rate as the body anticipates physical activity. Additionally, nicotine can constrict blood vessels, leading to an increased workload on the heart, which also contributes to elevating heart rate.

Understanding that nicotine is a stimulant helps clarify why the other options are less accurate. The assertion that nicotine only decreases heart rate does not align with the physiological effects observed in users, while the idea that it has no impact or that it both increases and decreases heart rate misrepresents the consistent stimulatory nature of nicotine on cardiovascular functions.