It is clear that the human body is good at adjusting and fine-tuning itself in response to immediate need. What in-built "amplification" do we have when intelligence is needed, and how could it be harnessed?

For example: The natural fight-or-flight reflex appears to provide instant alertness and focus, and I would imagine blood-flow to decision making functions is enhanced? Linked to a comment below I have found my reaction time and competance at rapid reaction computer games improves rapidly following surges in adrenaline. Is this coming from the improved focus (could this be simulated?), or increased bloodflow?