When people say their crush or partner has them feeling “some type of way,” we typically assume they mean loved, fulfilled, or maybe even turned on. What they don’t usually mean is scared, but according to science, the reason you feel butterflies in your stomach would indicate you actually are — or at least pretty stinkin’ stressed. David Barbour, the co-founder of health and wellness site Vivio Life Sciences, helped us break down the biology.

Couple in love

The brain’s limbic system, sometimes referred to as the “emotional brain,” reacts to certain stimuli in a primitive “fight or flight” response. The hypothalamus is part of this limbic system, and one of its main functions is to then route data from the limbic system to the autonomic nervous system (ANS). The ANS controls unconscious and necessary bodily functions such as breathing and digestion. This system is composed of three parts: the sympathetic nervous system, often referred to as the “fight or flight” system; the parasympathetic nervous system, or the “rest and digest” system; and the enteric, or gastrointestinal, nervous system.

Enter: the butterflies. “Butterflies, in effect, are the ANS switching its focus from all three [of its] branches to one system, the sympathetic system,” Barbour explains. This “fight or flight” system developed as an evolutionary tool to increase our chances of survival during times of extreme stress. And — believe it or not — coming in physical contact with or even just seeing your crush qualifies as an acute stressor.

As the ANS focuses in on the sympathetic nervous system as a response to the stressor (i.e., bae), its other two portions — the parasympathetic and enteric nervous systems — are affected by the shift. For this reason, blood flow to your stomach is restricted, adrenaline kicks in, glucose molecules are emitted from the liver and other organs, and heart rate increases. Add all these things together, and you end up with a tingling sensation in your stomach.

When that flip-flop feeling in your stomach isn’t occurring because of something bad like, say, a threat to safety, which is another possible trigger of the fight or flight system, it can actually be kind of enjoyable or exciting. But don’t expect butterflies to last indefinitely. And despite how Hollywood makes it seem, Barbour says it’s not a bad thing if you stop getting butterflies around your S.O. as you get to know them better and feel more comfortable around each other. “Your reaction is less visceral, it scares you less,” Barbour remarks. “If you had a butterfly sensation every single time you saw a significant other that would be a serious impingement on normal physiological activity.”

What gives you butterflies? Tweet us @BritandCo!

(Photo via Getty)