You'd know it anywhere: that squirmy, ticklish feeling in your stomach that's a sure-fire sign you're about to take a big test. Or that you're standing on a high ledge. Or that you've just locked eyes with your crush. Isn't it strange that you get the feeling that you've got butterflies in your stomach in all sorts of vastly different situations? Once you know what causes it, you'll understand why the sensation is so one-size-fits-all.
Don't Sweat It
You've probably heard of your "fight or flight" response, but have you heard of "rest and digest?" These are nicknames for each branch of your autonomic nervous system, which controls bodily processes without your conscious input. "Fight or flight" comes from the sympathetic division, which prepares your body for emergencies by increasing your heart rate, widening your airways, and making your palms sweat and pupils dilate. The parasympathetic division has the "rest and digest" moniker because it's what controls your body during ordinary situations. In essence, it's the yin to the sympathetic yang: It slows your heart rate and breathing and decreases your blood pressure.
But in order to help you survive an emergency, whether that's a saber-toothed tiger or a parking attendant approaching your illegally parked car, your sympathetic nervous system has to make some sacrifices. When it sees danger coming, it triggers the release of adrenaline and cortisol, which increases your heart rate and shunts blood to your heart and leg muscles — and away from your digestive system. The blood vessels surrounding your stomach and intestines constrict and the digestive muscles contract. It's that drop in blood flow that makes you feel like winged insects are fluttering around in your stomach.
Another unpleasant side effect you may experience in moments of panic is a sudden need to use the bathroom. As strange as it seems, that also helps ensure your survival. While the sympathetic nervous system causes most of the muscles in your digestive system to contract, there's one it relaxes: the internal anal sphincter, a muscle that, when contracted, keeps everything from coming out. When your fight or flight response tells that muscle to take a load off, well, it does just that. After all, if you were being chased by a dire wolf, you'd want to shed any excess liquids or solids to help you run faster. Your sympathetic nervous system is just trying to help.
Romance and Roller Coasters
Ok, but why do you get the same fluttery feeling when you're strapping in for a skydive that you do when you go on a promising second date? The latter is definitely not an emergency, but it appears that nobody told your sympathetic nervous system. All the same symptoms are there: dilated pupils, a racing heart, sweaty palms. Well, considering the fact that procreation is the end goal of evolution, it makes sense that the sight of a potential mate is an emergency situation for an organism like you. All of those heightened feelings encourage you to make a move and "lead to having a physical sensation of craving and the desire to focus your attention on that specific person," clinical sexologist Kat Van Kirk, Ph.D., tells CNN.
This highlights a strange truth: Emotions don't exist in a vacuum. A racing heart and sweaty palms might be the feeling of fear when you're in the path of an oncoming car, the feeling of excitement or nervousness when you're standing in the wings on opening night, and the feeling of lovesickness when you're gazing across the table at a new flame. Your body reacts the same way to each of those situations; it's how you interpret them that matters. Luckily, you can use this to your advantage. The next time you're a bundle of nerves before a big performance or an important meeting, reframe the feeling: Think about how incredibly excited you are about the opportunity. That way, you can channel all that sympathetic nervous system energy into doing your very best.
This article first appeared on Curiosity.com.