When Kyle Burg held my hand for the first time on the school bus in second grade, or when I saw N*Sync in concert for the first time, or when I asked my now ex-boyf if he wanted to hang out or something. All of those moments had one very distinct thing in common. I felt like I had to shit myself and throw-up at the same time. The more romantic description of that strange sensation is feeling butterflies in your stomach. It’s the same feeling you get on roller coasters or any other of those recreational death machines. There’s a fluttery feeling like someone is tickling you from the inside… a nightmare. But what is actually happening when we get these so-called butterflies?

The human body is capable of looking after itself without too much thought. Our automatic nervous system (ANS) regulates heart rate, blood flow and the distribution of nutrients around the body without you having to do anything. Ugh, could you imagine if we had to think about doing that stuff? When would we have time to watch Instastories for 3 hours straight.

The ANS can be split into two roughly equal branches—the sympathetic and the parasympathetic, or the “fight-or-flight” and the “rest-and-digest” branches. Both branches of the ANS are constantly active and act in opposition to each other.

The fight-or-flight system is responsible for increasing your heart rate, while the rest-and-digest system decreases it. So, the rate at which your heart is beating is the balance of the activity of the two branches of the ANS.

So what’s this got to do with butterflies? One of the major roles of the ANS is to prepare you for what it thinks is about to happen. So when you feel like you’re in danger, your “fight-or-flight” system kicks in and becomes dominant over rest and digest activity. This also causes a release of adrenaline, which both increases your heart rate (to pump more blood and faster), releases huge amounts of glucose from the liver, and shunts blood away from the gut. The blood is redirected toward the muscles in the arms and legs which makes them ready to either defend you or run away faster…. Hence “fight or flight”.

However, this acute shortage of blood to the gut does have side effects—slowed digestion. The muscles surrounding the stomach and intestine slow down the mixing of their partially digested contents. The blood vessels specifically in this region constrict, reducing blood flow through the gut.

While adrenaline contracts most of the gut wall to slow digestion, it relaxes a specific gut muscle called the “external anal sphincter”, which is why some people, like myself, feel like they have to poop when they’re nervous. This reduction in blood flow through the gut, in turn, produces the oddly characteristic “butterflies” feeling in the pit of your stomach. It senses this shortage of blood, and oxygen, so the stomach’s own sensory nerves are letting us know it’s not happy with the situation.

So why do we call it butterflies? It certainly does feel like and get described as “fluttering” by a lot of people, and I guess “gaaahhh make it stop!”  just doesn’t sound as fun and flirty. 

The next time someone gives you butterflies, get them a TUSHY to let them know they're the one that makes you have to poop. How romantic?