What effect does a stimulant like caffeine have on the heart rate?

Caffeine is a well-known stimulant that primarily affects the central nervous system. When consumed, caffeine can lead to an increase in heart rate, a response often referred to as tachycardia. This occurs because caffeine blocks adenosine receptors, preventing the inhibitory action of adenosine, which typically promotes relaxation and sleepiness. In doing so, caffeine enhances the release of neurotransmitters like norepinephrine and dopamine, which can stimulate the heart and elevate heart rate. These physiological changes result in a noticeable increase in the heart's activity, making the choice of an increased heart rate as the effect of caffeine both accurate and well-supported by scientific understanding of how stimulants operate in the body.