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musiciatee · 6 years

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What happens in my body during fight or flight?

Okay kiddos, i had the experience of suffering through endocrinology and as unpleasant as it was, our unit on stress was incredibly interesting. And considering how much we love torturing our characters, I figured I’d just make a quick post detailing what physically happens in the body as a response to stressful stimuli so you don’t have to go googling! (All the info gathered is directly lifted from my notes but if anyone wants me to, I can 100% go searching for journal articles to back this info up!).

So there’s not really a good definition of what stress is, but the National Institute of Mental Health defines it as “...how the brain and body respond to any demand.” This “demand” can come in the form of any sort of change in the environment. Your body remains in a state called “dynamic equilibrium”, your body still goes through some changes but not ones that are so extreme that it initiates a significant response to that change. But say that change does happen, this is caused by a noxious stressor. The noxious stressor stimulates an adaptive (or stress) response to try and reinitiate that dynamic equilibrium.

There are two systems, or two waves, to the stress axis. The first is classic fight or flight, and the second is the HPA (Hypothalamic, Pituitary, Adrenal) axis.

FIGHT OR FLIGHT: concerns the sympathetic nervous system (sympathetic neurons are typically associated with peripheral nerves, which are all the nerves except for basically your brain and spinal cord)

Within the fight or flight response (i’m just gonna refer to it as FF) there are two subdivisions: direct stimulation and indirect stimulation.

DIRECT: innervation (neural stimulation) via the sympathetic nervous system, stimulating organs such as the heart

INDIRECT: stimulates tissues in the adrenal glands to increase production of those good ol’ stimulatory neurotransmitters, epinephrine (E) and norepinephrine (NE) into circulation.

So I won’t bore you with the details but basically E and NE get released into circulation and bind to receptors that result in a variation of actions

increased visual activity

the brain actually takes like, snapshots of what you experience to try and make sense of what it is you’re actually experiencing, and when you’re in a stressful situation, the brain takes in more frames per second, which results in the sensation of time slowing down

increased brain blood flow

more blood to the brain theoretically enhances your ability to think and make those important life or death decisions that you need to make in a matter of seconds (i.e. whether to fight or flee).

increased arousal

not the sexual kind though, the body actually tends to shut down reproductive actions in stressful situations cause you don’t need to be makin’ babies when a predator is after you. This is arousal in the sense of being stimulated by your surroundings. You’re more alert, your senses are more acute.

increased gas exchange in lungs and cardiovascular activity

basically u be breathing real hard and heart be pumpin’

vasoconstriction in periphery and vasodilation in muscles, brain, heart

so this kinda goes back to what i was saying with reproduction! blood is basically rerouted from systems like digestion, reproduction, anything that isn’t absolutely necessary for fighting or running. If it’s not skeletal or muscular, that blood can be used elsewhere.

HPA AXIS: this is basically what happens in the brain, and while it’s fascinating, I’m not entirely sure you’d be able to write anything for your character on the basis of what’s happening on a molecular level in their brain, you know? (i mean i can totally add this in if y’all are interested lmao). But basically it’s a mechanism between the hypothalamus in the brain, the pituitary gland (also in the brain), and the adrenal glands that sit atop your kidneys.

what happens is that this axis culminates in the increased circulation of glucocorticoids (GCs- a class of steroid hormones) such as the ever famous Cortisol. GC actions typically have a longer lasting effect than direct action taken by neurotransmitters.

Increased blood glucose levels

this is exactly what it sounds like. Glucose, a simple sugar and the main energy source for living organisms, is released into the blood stream to help supply energy to the cells that need it

decreased metabolism and digestion

you don’t need to be wasting energy digesting or metabolizing anything if you’re trying to survive, basically. all your energy will be deviated away to more important systems.

the immune system is inhibited

which really sucks, but makes a lot of sense if you think about it! people who are chronically stressed or are stressed out for long periods of time are more prone to get sick. again this is just the body’s way of trying to decide what systems are and are not worth energy waste.

decreased inflammation (kinda goes with the immune system inhibition)

okay so i think this one is super cool and probably really helpful for writers who like... maim their characters. Usually if you get cut or wounded, the body’s first response is to release hormones like histamine (hence taking antihistamines to reduce swelling), bradykinin, and prostaglandins. These hormones cause blood vessels to kinda “leak” fluid into tissues, which is the cause of swelling. This helps to isolate bacteria and other foreign substances from further exposure to other tissues. These hormones also signal to white blood cells to come and attack any germs and dead/damaged cells.

But when you’re engaged in this HPA stress axis, this inflammation is decreased, so say your character was stabbed in the leg but managed to get away without completely noticing that they were stabbed in the leg. that character could realistically run on that leg for a little while because there’s no (or rather there’s little) signalling for that inflammation cascade. SO LONG as the thing that stabbed them is acting as a stop to prevent bleeding out (arteries are bitches). Or maybe your character breaks their foot while still high on adrenaline, they’d be able to run on that for a little while (they’ll definitely feel it, this whole response doesn’t prevent pain reception, it just allows the body to push past it for a little while until you’re away from danger).

behavior is obviously altered (another post entirely could be made describing this)

long exposure to stress can shut down growth and reproduction

this makes a lot of sense if you think about everything we’ve covered thus far! tl;dr the body plays a lil game of eenie meenie minie moe (this is the technical language, yes) and decides what systems are most beneficial to survival, and if it’s deemed unnecessary, energy is deviated away from that system.

as an example: if your character is in a freezing cold environment, blood flow and circulation (and thus, heat) are pulled back from the extremities and into the torso where more internal organs are located.

Ultimately, we all know that too much stress is really bad for us, but it can literally rewrite our DNA. Our DNA is capped with these nifty things called telomeres (they’re basically repetitive nucleotide sequences at each end of a chromosome, which protects the end of the chromosome from deterioration or from fusion with neighboring chromosomes). Each time a cell divides, telomere length shorten a lil bit, so naturally with age, they get shorter. But it was found through a study by Dr. Elissa Epel that stress accelerates the shortening of telomeres, which accelerates the aging process.

So that character who’s been through a lot? That harried look of fatigue and age? Totally legit.

BUT WHAT’S REALLY COOL is that it was shown that healthy coping habits, especially those that align with social support like showing compassion and genuine caring (it’s important that it’s genuine, studies have shown that it doesn’t work if the care shown is disingenuous) can counteract the physiological and psychological effects of chronic stress.

I hope this was somewhat helpful to you writers!!! if you have any questions or need help applying science to your writing (or even coming up with some pseudoscience!) my proverbial door is always open!!!

#shut up ang #if there's anything that seems inaccurate pLEASE CORRECT ME!!!!#how do i even tag this??#writing reference #writing #lmao someone help me tag this pos

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