The possibility of you having a unpleasant feeling of nausea and trembling deep in the gut when something uncertain is about to happen is equal to my mother saying “no” to double cream Oreo while in PMS.

Science often refers to the stomach as the “second brain,” based on findings that the gut contains 100 million neurons linking it to the brain, known as the brain-gut axis.

So, when we feel nervous before a stage debut or even a first date, the brain communicates that anxiety to the gut.

Most of us recognize this feeling by its un-scientific name butterflies in the stomach.

But, to fully understand the reasons behind the butterflies, we may have to look back hundreds of thousands of years.

Back in the days of our predecessor cavemen, when people had to be prepared to run from attacking lions (or other prehistoric beasts), an increased heart rate and tense muscles might have helped them make a quick escape.

Therefore, even though a job interview or meeting a person of your love interest isn’t necessarily a life-threatening situation, the body may deal with the stress the same way it handled the lion chase. It is strange, I know.
The digestive system is closely linked to a person’s thoughts and emotions, so those jitters can quickly turn into stomach circus acrobatics.

Rather than actual butterflies bouncing around your large intestine, of course, there is something sciency really going on — and it’s all down to your clever body systems. The one in charge of this — the nervous system.

The human body is capable of looking after itself without too much voluntary thought.

It quite happily regulates heart rate, blood flow and the distribution of nutrients around the body without you having to consciously intervene in any way – a process run by the autonomic nervous system (ANS).

We can look at the ANS as a control system that acts largely unconsciously and regulates heart rate, digestion, respiratory rate, pupillary response, urination, and sexual arousal. (Find it stress related much?)

The ANS can be split into two roughly equal branches — the sympathetic and the parasympathetic, or, as it is memorized by every first-year medical student, 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 sympathetic (fight-or-flight) system is responsible for increasing your heart rate, while the parasympathetic (rest-and-digest) system decreases it.
Let’s say that the rate at which your heart is beating is the balance of the activity of the two branches of the ANS.

The dominance of the parasympathetic branch is why you feel content and sleepy after a huge Sunday meal at your grandmother’s.

Quite of bit of blood flow from the heart is directed to the stomach, and your ANS encourages you to sit down for a bit to let digestion take place.
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. Back to our cavemen.

ANS actions give us an evolutionary advantage since if you see a saber-toothed tiger about to pounce, you don’t want your valuable oxygen-filled blood to be busy with your last meal.

Ideally, you would want this blood to be temporarily redirected to muscles in your legs so that you can run away slightly faster.
So, your fight-or-flight sympathetic system kicks in and becomes dominant over parasympathetic 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. 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 charmingly called kahm, external anal sphincter.

This little muscle guy in his relaxes mode is why some people report a pressing need to visit a bathroom for the number two when they’re nervous.

Or for a constant or other, as frequent urination is yet another flight or flight “side effect”. In a typical situation, when you’re not feeling nervous or anxious, the bladder is relaxed as it fills with urine from the kidneys. In contrast to our “normal”, the bladder’s external sphincter muscles might be closed to make sure that urine doesn’t leak out.

Also, ever felt a sudden urge to throw up before that interview? Sometimes those butterflies can turn into nausea because of that before mentioned adrenaline rush which can temporarily stop digestion.

Butterflies are usually harmless, but if these fight-or-flight feelings interfere with daily life, as a frequent nervous stomach may be a sign of an anxiety disorder or even a gastrointestinal issue.

One way to deal with butterflies is to convince the body that it’s not in actual physical danger. Take a deep breath and relax. Unless you’re eyeing a position as a flame-thrower in the circus, job interviews aren’t really that dangerous, right?

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