After an adrenaline rush, why do humans experience a sudden severe drop in energy? Would this not be disadvantageous for primitive survival?
In: Biology
An adrenaline rush is literally pushing the human body’s responses into overdrive. Pain impulses are deadened, allowing the person to react faster, farther, and more forcefully to the perceived threat (this translates into higher speed, strength, and stamina during the rush). Also, neurons in the brain and certain nerve pathways fire more rapidly, which translates into the closest thing biology can call an increase of time (which heightens reaction speed). Things that don’t contribute to actual survival in the extreme immediate future get essentially turned off, including digestion and sphincter control.
This all has side effects. First of all, you caused yourself microinjuries during the adrenaline rush, and depending on what you did during the rush, you may have caused overstress injuries on a larger scale too, as bones, ligaments, tendons, and muscles were pushed beyond your day-to-day limits (just because a 90-lb granny can lift a car off a baby doesn’t mean she gets away with it scott-free). You’ve also exhausted some or all of the ready energy supplies in your bloodstream (because digestion got paused), and that needs replenishing. Oh, and your guts need to start up again. Lastly, adrenaline is long-term toxic to the body, and needs to be metabolized and removed. Recovering from the microinjuries, removing the adrenaline, and replenishing the bloodstream energy reserves makes you feel drained and you need recovery time. (the exhausted feeling is because you burned up all the energy and have an excess of what are called ‘fatigue poisons’)
As for this being disadvantageous to primitive survival, it isn’t, not really. An adrenaline rush gives you the chance to escape an immediate life-or-death situation, and most of the time, you only encounter one of those at a time. the chance of repeated or constant life-or-death situations is low enough that adrenaline rushes are something selected for in an evolutionary sense–the early animals that HAD adrenaline rushes were much more likely to survive than the ones that didn’t. (Before you ask, I said animals, because there’s a large amount of evidence to suggest adrenaline rushes predate mammals–look at birds and their panicked flight when startled, much faster than their usual speed, for an example. this suggests that it’s likely some dinosaurs also had a similar mechanism.)
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