the limbic system
- Melinda
- May 23
- 14 min read
Updated: Jul 29
the limbic system
The limbic system. Personally, I think it's a wildly interesting subject and one I really enjoyed writing about, but in all honesty? Skipping this 13-minute read might be a good call—for some. If you're anything like me, however, and enjoy knowing the why of things, then I invite you to read on because I labored over this novella for far too many days with you in mind.
In this post, I'll be focusing specifically on what happens when you inhale essential oils, and how these drops of fragrant plant essence—via your sense of smell—can influence the body's stress response. I think it only fair to preemptively warn you that I'm about to unabashedly geek out just a little bit because I love this stuff. But just as I was getting ready to launch into a comprehensive list highlighting why, I realized it all boils down to this: it's just really, really cool. And while I understand that cool is utterly subjective, how essential oils work with and within the human body to effect change is so fascinating to me that I felt compelled to share it here. With you. In the hopes that you'll find it just as fascinating and enlightening a subject as I did.
exams? meh.
There was a tremendous amount of study involved in becoming certified as a holistic aromatherapist. I had anticipated that my journey would stretch me intellectually—which it did. I'd also had high hopes that it would be stimulating, challenging, and useful to my daily life—which it was. And were you to ask me my overall assessment, I'd say that it was an extremely rewarding experience, and one that I'm grateful for nearly every day (she says, reaching for her bottle of ylang ylang...). But if you were pressing me to be completely honest, then I'd also have to share with you that each and every aspect of it didn't exactly thrill me to no end.
The history of aromatherapy was interesting. And morphology—selecting essential oils based on the part of the plant they come from—gave me some new things to consider. Chemistry was... you know, chemistry. Memorizing the properties of countless oils was wildly empowering, yet numbingly tedious. Exams? Meh. Blending? Super fun. Writing a paper? Super stressful. But when it came time to tackle Anatomy & Physiology? Well, I'm pretty sure Cupid shot an arrow into my ass as soon as I cracked open that text (no pun intended), because I was instantly smitten. A hopeless goner. Head-over-heels in love.
are you kidding me?
My family humored me, but I think I probably drove them crazy with the endless facts. Day after day, I offered up enthralling tidbits that I assumed they would be equally awed by. I imagine that I spent more time immersed in that section of the training than most students do, but the human body is freaking amazing, y'all. Really, it's perfection. So many parts working in harmony. So many crazy-tiny details that keep things running smoothly in the face of endless obstacles and interference. So much growth, change, and constant renewal.
Honestly, it has the vibe of science fiction. But it's real. It's you and it's me, living in a body that grows from a minuscule egg into a fully formed human, magically repairs itself on the daily, and maintains so many vital functions without our active participation or awareness. As enraptured as I was, however, it also made me frustrated. Frustrated because we take this amazing machine for granted, expect it to thrive no matter how badly we treat it, and then bemoan the cruelty of "fate" when something malfunctions. Fate? Are you kidding me? It'd be funny if it wasn't so damn depressing. I mean, the fact that we're still alive in this chemical-laden world we've created—eating non-foods on the daily—is nothing short of a miracle. And reading through that 358-page text (multiple times) made me fall in love with the human body all that much more. Which, honestly, I didn't even know was possible.
ya weirdos
While I found all of it fascinating, today I'm only going to talk about two parts in particular. And I promise I'll refrain from digging too deeply because I'm aware that not everyone loves this how-the-body-works stuff quite as much as I do (ya weirdos). But when it comes to essential oils and how they can impact our mood, it's important to understand that I'm not talking some "New Age nonsense" here—I'm talking science. And it all starts with our sense of smell and how it interacts with something called: the limbic system.
If you're anything like me, you have absolutely no idea (seriously, no idea) what the limbic system even is. Most of us are at least superficially familiar with the nervous system, the reproductive system, and the muscular system, but the limbic system? I hadn't a clue. Which seems like a huge educational oversight once I began to understand the role it plays in, well, virtually everything.
This system of the body includes quite a few structures, and its primary jobs are to regulate the body's stress and emotional responses, and to process memories. It also deals with a host of other things such as learning, olfaction, sleep, appetite, behavior, and motivations. While not everyone can agree on the parts that make up this crucial system, here they are as I learned them (plus one). I've included a brief description of their individual jobs (because it's cool), but it's predominantly the amygdala, the hypothalamus, and the olfactory bulb that are relevant to this post.
components of the limbic system
amygdala: deals with regulating emotional responses, fear, anxiety, aggression, male sexual motivation, and pleasure
hypothalamus & pituitary gland: these two work together to maintain homeostasis (balance) within the body through control of the autonomic nervous system, the neuro-endocrine system (hormones), and the limbic system
olfactory bulb: deals with our sense of smell
hippocampus: deals with learning and memory, is where short-term memories get turned into long-term ones, and plays a role in turning off the stress response
thalamus: a relay station for all sensory stimuli (except for the sense of smell, which is relevant to this post!)
septum: plays a role in inhibiting aggression
mammillary bodies: believed to add the element of smell to memories, and are involved in maternal behaviors
ventral tegmental area: the natural reward center of the brain that's involved with the release of dopamine and plays a role in addiction, motivation, depression, intense emotions, and several psychiatric disorders
nucleus accumbens: is also involved with the release of dopamine, and plays a role in reward, pleasure, laughter, addiction, fear, aggression, and the placebo effect
prefrontal cortex: deals with impulse control, long-term planning, delayed gratification, learning appropriate sexual behavior, learning when to be appropriately aggressive, and plays a role in empathy
These structures that make up the limbic system are all located in your brain and, in large part, deal with your roiling, tumultuous, ever-changing human emotions. These parts are linked via various pathways of communication, and their collective intention is to generate some type of reaction. This reaction, depending on the situation, may be behavioral (you run), emotional (you feel sad), or cognitive (you rationalize) in nature. The "problem" is that as these various parts interact with each other, they often have very different ideas about what that reactionary output should be. So before a reaction can be generated, one of those limbic parts has to be the first to influence the head honcho of them all: the all-mighty hypothalamus.
and the winner is...
While each of these parts has an opinion, ultimately, it's the hypothalamus that will trigger the body's response to whatever stimulus—real or imagined—is being presented to you. Consequently, the first one to reach the hypothalamus is the one whose voice is most likely to be heard. The amygdala would like you to react emotionally. The prefrontal cortex would like you to react rationally. But who gets the prize? Will it be the nucleus accumbens and the addiction is fed? Will it be the prefrontal cortex and reason prevails? Or will it be the amygdala and road rage ensues?
Let's work with this as an example: Imagine that you're out on your leisurely morning walk, whistling a happy tune as you stroll along. The sky is blue, the birds are singing, and all is right with the world. Just as you're passing the house-next-door, however, you abruptly choke on your whistle the moment you spy a rabid raccoon "wrestling" with the five-year-old grandchild of your neighbor. In an instant, you register that the sweet, little cherub who always waves hello to you is being taken down by a masked beast. An excessively drooling masked beast currently overcome by rage, pain, viral infection, and dehydration. The child is powerless. The raccoon is vicious. Quick: what do you do?
a true hero
Via your eyes and a series of synapses, the amygdala registers this info almost instantly, processes it, and decides that danger is definitely present. The amygdala then dispatches a fevered warning to the hypothalamus. There could potentially be many emotional reactions here—fear, panic, and/or anger to name just few. But let's pretend this scenario is making you mad as hell, and pushing you to aggressively confront the snarling creature. The amygdala is screaming at you to do something already, while the septum is over there trying to keep that aggression in check. And the prefrontal cortex is doing its best to remind you of when it's appropriate to be aggressive and when it's not. And the hippocampus is frantically trying to remember if this sort of thing has ever happened to you before, and if it did, how did you fare? Synapses are firing, many parts are vying madly to be heard, and for just a split second you stand there frozen.
Who's going to get to the hypothalamus first and initiate a response? My guess, in this case, is that the sympathetic nervous system is quickly activated. And as adrenaline surges through your veins, you run towards the scene of the crime, clobber the rabid raccoon over the head with a shovel, scoop up the cherub, and run for the hills. The amygdala wins the race, and you—in true hero's fashion—save the day.
In this situation, the amygdala winning is obviously a good and beneficial thing (even though you're both in need of a rabies shot now). But when it comes to triggering the stress response, the amygdala often wins the race, even when it's wildly overreacting. Even when the situation isn't even in the ballpark of live-or-die.
Like just the other night when I was watching a (very bad) movie with my husband, and I felt something crawling up my leg. Unconcerned, I looked down and prepared to brush away an ant, maybe a friendly jumping spider, or perhaps one of the many summertime beetles. Instead, I found an enormous, above-average-sized cellar spider crawling leisurely across my knee. In that instant, my prefrontal cortex was reasoning that it was completely harmless and to be careful I didn't crush the poor creature. And my hippocampus was simultaneously reassuring me that, in all of my fifty+ years, there was no memory of having ever been bitten by a spindly cellar spider. But while many limbic parts were simultaneously communicating with me, all I truly heard was my amygdala screaming in unfounded terror: OH MY GOD WE'RE GOING TO DIE!
seriously?
Die? Seriously? But did I behave rationally? No, I most certainly did not. I freaked out. And while I'm not generally a shrieking kind of gal, I'm pretty sure I let out a shriek. I brushed it away none too gently and then, with heart pounding, spent the rest of the movie watching for the "killer" to reappear. Not only that, but my overreaction created an emotionally-charged memory that my hippocampus then stored, and for the next several days every sensation I felt was now suddenly a harmless spider intent on doing me in. The amygdala "won," but I actually kinda felt like I lost (even though the spider did survive the assault and continued to live quite happily in the corner of my living room).
Kudos to the amygdala, though, because it's only trying to keep me alive in a world rife with dangers. The problem, however, is that we can trigger that exact same fight-or-flight (sympathetic) reaction to things far less life-threatening than rabid raccoons—like harmless cellar spiders. Or even worse, mere thoughts.
The amygdala deals with strong emotions, particularly those related to fear and anxiety, and it has the ability to influence how your nervous system will react to those unstable emotions. Maybe you're actually faced with a rabid raccoon and it saves a life, but how often is the threat real in comparison to threats only imagined (as in the case of worrying about things that never actually come to fruition). And how often do humans work themselves into a tizzy—a full-on sympathetic reaction—over absolutely... nothing? Basically, it often feels as though those two tiny almond-shaped bundles of nerves are calling the shots, does it not?
But what if I told you there was a way to influence the amygdala in your favor? A way to quiet that sympathetic response? In order to do that, however, we'll first need to link the sense of smell to the limbic system. It all starts with a scent—tiny chemical particles—that enter your nostrils and attach themselves to the receptors in your nasal cavity. Through a series of events, this triggers a nerve impulse in the olfactory bulb which is then sent directly to... the amygdala. And what exactly is the amygdala going to do with that aroma? Decide—in a split second—whether or not the info it just received warrants a stress response.
stop, drop & roll
Say, for example, you wake up in the middle of the night to the heavy smell of smoke. Before you're even fully alert, that particle of smoke drifted up your nostril and found its way to the amygdala. The amygdala is in communication with the hippocampus, who quickly rummaged through your memories to see if you've reacted successfully in a similar situation before.
Regardless of whether or not anything is found, your amygdala makes the call and decides that smoke + middle of the night = danger. This danger signal is then shipped off asap to the hypothalamus which then responds by triggering a stress response. The sympathetic nervous system fires up, your body floods with adrenaline and oxygen, you leap out of bed, wake the household with your screams, grab the cat, and run like hell. And remember: this cascade of events all began with a smell.
Instead of smoke, let's say you wake up to the smell of an apple pie baking. When those particles hit your nostrils, once again the amygdala communicates with the hippocampus, but this time the hippocampus finds an emotionally-charged memory. It remembers Grandma's house on Thanksgiving. It remembers being surrounded by cousins, aunts, and uncles. It remembers laughter and warmth. In this case, the reaction is quite different altogether. Instead of running like hell (sympathetic), you're filled with a warm, fuzzy, happy, and calm feeling (parasympathetic). You stretch out in bed, relax, smile, and take a walk down Memory Lane. And once again: this much more pleasant cascade of events all began with a smell.
hideous river disease
Let's play with one last scenario and imagine that one day you inadvertently work yourself up into a lather obsessing over some future possibility. Maybe you're worried about money, whether or not your lover is cheating on you, why your child is suddenly acting out, or if the dog is so lethargic because he drank out of a stream last week and he's now dying of a hideous river disease. Remembering that our bodies can react to imagined stimuli just as effectively as they can to real, physical danger, you're now feeling the effects. There's a sick knot in your stomach. Your heart is beating faster, and your chest is tight. Your pupils dilate. Your breathing speeds up, and that muscle in your eyelid starts twitching like mad.
Cued by a mere thought, your fight-or-flight is kicking in. But with no raccoon to clobber and seemingly no way to shut up your obsessive thoughts, your body is preparing to fight an endless battle with an invisible enemy. And there seems to be no way to tell your nervous system to stand down already.
cue the aromatherapist
Until I hand you an aromatherapy inhaler filled with anxiety-relieving oils, and tell you to close your eyes and inhale deeply for five minutes or so. Those aromas will travel the same pathway as that smoke and apple pie did. But when they hit your amygdala, the chemical cocktail in the essential oils gives it the message that things are okay. It's safe for the soldiers to put down their weapons because, quite suddenly, the amygdala no longer feels pressed to warn the hypothalamus of impending danger. And thus? You've just interrupted the stress cycle. With a smell.
Not only does smell work, it works quickly and efficiently because smell is the only one of the senses to have such direct communication with the amygdala. All of the other senses are required to make three or four stops before the info has been processed and reaches the hypothalamus to generate a reaction (like your eyes registering that rabid raccoon or your ears hearing grand-baby scream). But smell? Smell is only one synapse away. Which, to me, means that the creator of these most amazing bodies deemed our sense of smell critically important. I can't claim to know why, but I can claim that we can avail ourselves of it. Are you beginning to see the implications of this? Smell may perhaps be the most undervalued and underutilized of our senses. Until you meet an aromatherapist, that is (happy to make your acquaintance).
Rest assured, I already told you that I'm not about to veer off into some of my "witchy shit," and I'm not. Because we're still firmly in the realm of science. Essential oils work because plants know their business. And in order to preserve their own health, they emit chemicals—chemicals that we know as: essential oils. Potentially hundreds of chemical compounds make up each and every essential oil—things like monoterpenes, sesquiterpene alcohols, esters, aldehydes, ethers, and ketones. The plant uses these naturally-occurring volatile organic compounds (VOCs) for a variety of health reasons and, lucky for us, they can potentially improve our health as well. And have been doing so for thousands of years.
studies? really? (yes)
Studies have shown, for instance, that essential oils like lavender and sweet orange can decrease stress, bergamot can improve sleep, and Roman chamomile can have a calming effect. And those are just several of the thousands of studies currently on PubMed. (Did I just spend an hour of my life reading through studies? Perhaps...)
So if we know that smell can influence the stress response, and that far, far too many of us are suffering from dangerously chronic stress, then shouldn't we all be exploring this sense for daily support? Especially when it's estimated that up to 90% of illness and disease is attributed to stress? Essential oils offer this kind of support and can be available at any time of day or night through something as simple as an aromatherapy inhaler, or aromatic diffusion. Diffusing essential oils is as simple as pressing a button and walking away. And aromatherapy inhalers are quick to assemble, cheap to make, able to be used by virtually anyone, don't cause nasty side-effects, and are small enough to slip into your pocket. Just imagine how much chiller—and vibrantly, naturally fragrant—the world could be if we were all packing inhalers. Happy, wistful sigh. I can smell it now...
quick commercial break
(Quick commercial break here, because have you signed up for our newsletter yet? I compiled a 30+ page booklet—9 Essential Allies—that features nine common essential oils and is jammed with dozens of recipes and info! Why do I mention this now? Because there are seven aromatherapy inhaler recipes tucked away in those pages. And did I mention it's FREE? All you gotta do is sign up for our weekly newsletter! And we now return to our regularly scheduled program...)
I know that was an awful lot to take in—perhaps too much—so I feel like it's time to wrap up science class for today. But wasn't that fun? (You don't have to answer that.) And if this whole subject has piqued your interest too, then here are a couple of short videos that I found interesting:
Limbic System (I had to watch this one for my course and while it's very long, it's also so interesting that I've watched it multiple times!)
And that'll do it for today, friends. Hope your day is a happy one, and if not? Maybe go smell something pretty :)
Much love,
Melinda
Level 3 Holistic Aromatherapist
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