A person feels progressively drowsy throughout a long day of work. They consume a beverage containing a common stimulant, and shortly after, their feeling of drowsiness subsides and they feel more alert. Which statement best analyzes the primary neurochemical reason for this change?

A student studying late at night feels increasingly drowsy as a natural, sleep-promoting chemical builds up in their brain. They drink a caffeinated beverage and, shortly after, feel more alert and awake. Which statement best explains the primary mechanism responsible for this effect?