Caffeine causes most of its biological effects via antagonizing all types of adenosine receptors as does adenosine, exerts effects on neurons and glial cells of all brain areas. In consequence, caffeine, when acting as an adenosine receptor antagonist, is doing the opposite of activation of adenosine receptors due to removal of endogenous adenosinergic tonus. Besides adenosine receptor antagonism, xanthines, including caffeine, have other biological actions: they inhibit phosphodiesterases, promote calcium release from intracellular stores, and interfere with GABA-A receptors. Caffeine, through antagonism of adenosine receptors, affects brain functions such as sleep, cognition, learning, and memory, and modifies brain dysfunctions and diseases.
Basically put, it has the same properties as an energy regulator in our brain. Because of that it takes the place of that regulator by binding to the receptor sites, basically blocking it from doing it's job. With the caffeine blocking adenosine it does allows energy to be ramped up without any moderation. It causes your system to just release the available energy that it has in storage, as it normally should for just in case needs.