After an adrenaline rush, why do humans experience a sudden severe drop in energy? Would this not be disadvantageous for primitive survival?
In: Biology
For context: I was driving in the snow and almost lost control and narrowly avoided ending up in a ditch. Naturally, a huge adrenaline rush. A half hour into the drive later I was very drowsy, despite having drank a 5 hour energy just before leaving. This is not the first time this has happened either.
The question implies that humans typically experience a “sudden severe drop” in energy after an adrenaline rush, but the reality is we do not: the body simply goes back to normal. Your sudden drop in energy is not a general after-effect of an adrenaline rush, it’s particular to your specific example and is not a generalised issue.
It is of course the case that, because your body releases increased amounts of energy during an adrenaline rush, your muscle-stored energy levels will be lower after a rush, but not to the extent that you are no longer functional, unless you were already in a low-energy state with no food in your system.
What might have happened here is that when your body is inundated with hormones during a rush, you suddenly become much more alert than you were and your feelings of pain, tiredness, etc, are both muted and toned down by the hormones, so when the hormones’ effects are over you suddenly feel more tired in contrast.
Incidentally there is a now-known “let-down” effect after somewhat lengthy periods of heightened stress (you survive through a hectic week at work with a deadline on the Friday, only to collapse on the weekend and be sick) but this is a different issue altogether.
It would be disadvantageous, but consider the timeline:
You’re confronted with something that you identify as posing serious threat to your safety — be it losing control of a vehicle in the snow or pursued by a predator. Your body dumps adrenaline into your system which temporarily gives you a dramatic boost to your reflexes, stamina, and strength. This is the “fight” in the “fight or flight” reaction.
But you have to understand that the rest of the time, your own brain limits your body in what it can do so you don’t hurt yourself. Your body is far more capable than you know, but if you were to use that full extent all the time, you’d cause permanent damage to your joints, ligaments, etc, to say nothing of the fact that higher blood pressure (from increased heart rate) would take a long term toll on your body, and immune and digestive systems are suppressed during this “fight or flight” phase.
So the crash you feel is the price you’re paying for that boost that saved your life. It might put you at a disadvantage if you were confronted with another life or death situation, but the fact that it got you out of one is probably enough to genetically select for it over generations.
Edit: might as well fix those typos with the traction this is getting. Lotta people have pointed out that the “fight or flight” I refer to is a lot more nuanced than the binary representation I made. [This](https://www.reddit.com/r/explainlikeimfive/comments/ervkgl/eli5_after_an_adrenaline_rush_why_do_humans/ff6znvi) comment does a good job.
Consider you game character’s energy bar. He drained it quickly to use his ultimate. Now energy bar is low and will slowly fill up.
The ELI5 explanation is during an adrenaline rush you’re borrowing energy from your future self (or your reserves). So then you have an energy debt.
You’re presuming there is a drop in energy as though the adrenaline left. In point of fact, that exhaustion is the *result* of large amounts adrenaline.
Adrenaline causes the fatigue.
EDIT:
Side Effects of Adrenaline
* Dizziness
* Headache
* Perspiration
* Vomiting
* Anxiety
* Blurred vision
* Nausea
* Confusion
* Drowsiness
* Seizures
* Psychomotor agitation
* Loss Of Consciousness
* Lightheadedness
* Pallor
* Decreased urine output
* Severe sleepiness
That depends.
Adrenaline is used by the body in an emergency situation, to boost reaction times, apparent strength or access to muscle power, speed of that access, and dull pain responses for a limited time. The mechanism is deployed in such a way as to make it possible, or more possible for a human being to end a threat, or evade it in the moment. For longer duration exertion, only prowess and training can get you through, but if its a case of having to be able to bring that spear tip around, get it elevated right, and ram it into the leaping lions belly, or having to save yourself or someone else from falling off that cliff, right this second, it does a bloody spectacular job at it. Sure, you might have to rest afterward, and there may be situations in which that isn’t very practical, but that is why hunting parties used to be hunting parties, rather than just lone dudes trudging off into the wilderness.
Humans used to do an awful lot of endurance hunting. It wasn’t a case of standing on a cliff, dropping Bison and Elk from range with a bow. You had to get a spear into them, then chase them mile after mile, as their blood ran out and their energy drained. To do this effectively, and indeed to ensure safety for the group, this was done as a group activity. The reason for this is that say one guy used his adrenaline to spear the prey, and then the group gets attacked by a predator, the others can use THEIR adrenaline to counter the lion, then everyone makes off as well as they can, after the prey animal, tracking it by blood and hoof prints, and running along as best as they can, despite their adrenaline already having spiked. You also need to understand that having a modern perspective on adrenaline and how it operates on the generally weak people of today, can cloud your understanding of just what kind of people the ancient humans were.
They lived wild lives, and had endurance beyond the best runners we have on Earth today, as well as the capacity to run much faster over long distances than the world record holders on our planet currently. Now, not all of that is directly related to the adrenaline response, but… That greater hardihood and general physical capacity, was probably coupled with a very different, far more frequent adrenaline trigger, and a far smaller crash period afterward. Its very likely that the constant threat involved in living the wild lives our ancestors did, simply made it more like turning something on, then turning it off, several times a day, and thinking nothing of it.
The human being as a structure has changed enormously since those days, so its entirely probable that our ancestors could go on adrenaline spikes that would put modern man to shame, without much by way of crash consequence.
In addition to what people discussed, a long lasting “fight or flight” rush would actually be evolutionarily harmful. The fancy term for what you are describing is the sympathetic nervous system. This is what gives the boost. A byproduct however is the shutdown of the parasympathetic nervous system (which is responsible for digesting and rest). [Side note: there is a lot of fabulous research on the role of these nervous systems in PTSD. People with PTSD experience longer and more frequent sympathetic response and shorter, less effective parasympathetic responses].
Now while the sympathetic system is rushing, one of the parts of the brain who’s function is reduced is the frontal lobe. This is because your body is more worried about senses and perceptions (and responding to that input) then decision making, planning, or worrying about consequences. Let’s take an example of our ancestors being attacked by a bear:
Individual A: sympathetic system activates, blood rushes to muscles to either fight the bear or run from the bear. Once the immediate threat is reduced (i.e. gained distance from bear) speed is not as important and now tactics take over. Person A climbs a tree, hides somewhere, remembers what to do in case of bear attack. Higher chance of survival.
Individual B: sympathetic system activates but this time doesn’t turn off in time. This person keeps running (or fighting). Odds of beating a bear in an endurance match are pretty slim. Lower chance of survival.
These bursts are designed to buy us enough time to figure out the problem rather than solve the problem themselves. Now, could a long enough sympathetic response help us fight off a bear? It’s possible. But evolutionarily, survival depended on humans ability to outsmart the bear. Keep in mind, if you run from the bear then your sympathetic will activate, but the bear’s probably will not (chasing after someone is not really a strong flight or fight response). But attacking the bear will activate your sympathetic system AND the bear’s. This means everyone gets stronger, faster, and dumber. Humans lose their only advantage.
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TL;DR: your body uses an INTENSE burst of energy in a fight or flight response to avoid danger. Because so much energy is used, it must also be recovered. The adrenaline burst of energy is meant to get you out of emergent situations. Not longlasting dangerous ones.
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