An example of a stimulus may be a baseball. In a game of baseball, the ball acts as a stimulus in the event that the ball nearly comes into contact with the body of somebody not expecting it - for instance, someone sitting in the bleachers, unprepared for a foul ball. When the foul ball comes closer to the audience, the nervous system and muscular system work together to react to the stimulus and protect the body by attempting to shield oneself from potential harm, which can be anything from a slight flinch, to a dodge, to covering one's head with their hands.