answer:Caffeine affects your nervous system. “Caffeine belongs to the xanthine chemical group. Adenosine is a xanthine that is naturally occurring in the brain, used as a neurotransmitter at some synapses. Because of their relation, caffeine looks a lot like adenosine to nerve cells and therefore binds to adenosine receptors in the basal forebrain. The cells then can no longer sense adenosine because caffeine is taking up the receptors. Instead of slowing down, the nerve cells speed up and stop the person from getting tired. ” From University of Minnesota