Final answer:
Caffeine stimulates gastric acid secretion, increases heart rate by influencing the SA node, and is recognized for its sympathetic activation, leading to a variety of stimulatory effects on the body.
Step-by-step explanation:
Caffeine mainly acts in the brain but also stimulates gastric acid secretion, increases heart rate and is a diuretic. Caffeine, a central nervous system (CNS) stimulant, reversibly blocks the action of adenosine and stimulates the autonomic nervous system. This stimulatory effect is seen in various systems of the body, such as an increase in heart rate by increasing the rates of depolarization at the SA node and a promotion of gastric acid secretion. Moreover, caffeine's role in sympathetic activation contributes to bodily responses like pupil dilation and an increase in heart rate.