Name: なぜ私たちは胃の中で蝶々を感じるのか？| 蝶々が胃の中にいるのはなぜ？ (Why do we feel Butterflies in our Stomach? | #aumsum)
Uploaded: 2021-01-14T08:09:23.000Z
Duration: 5 min 37 s
Description: VoiceTubeの動画で発音を聞きながら英語表現を覚えよう！学べる英語：

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Why do we feel butterflies in our stomach?

Butterflies in our stomach are basically caused by our autonomic nervous system or ANS.

ANS regulates our involuntary functions like heartbeat, blood flow, digestion, etc.

Also, during stressful situations such as
when a ferocious animal comes in front of us.

A part of ANS called the sympathetic nervous system prepares our body for fight or flight.

This means, it redirects blood from other
parts of the body to mostly our hands and legs.

So that they get sufficient oxygen and nutrients and thus, help us fight or flight.

So then, why do we feel butterflies in our
stomach?

It is believed that since blood is redirected
from the stomach.

Millions of sensory nerves in it detect a sudden decrease in oxygen.

Hence, in response to this, the nerve cells
create the feeling of butterflies.

Also, because of blood redirection, it is
thought that the stomach contracts.

Thus contributing to the feeling of butterflies.

Mirage is an illusion in which it appears
as if there is water present on the ground.

On a hot day, the land heats the layers of
air closer to it.

However, as we move higher, the layers of
air get relatively cooler.

Thus, the hot lower layers of air near the ground form rarer media and cold upper layers form denser media.

Now, when light coming from sky travels from denser to rarer media.

It bends more and more until it exceeds the critical angle.

That is, the angle beyond which light gets reflected.

This phenomenon is called total internal reflection.

When this reflected light reaches our eyes,
our eyes trace it backward as a straight line.

Hence, the reflection of blue sky appears
on the ground and our brain thinks that there is water.

Rain is just water and water doesn't have
any smell.

The distinctive smell which frequently accompanies the first rain.

After a dry weather is scientifically called petrichor.

It basically comes from plants and bacteria called actinomycetes which live in the soil.

Now during a long dry spell, the plants release oils into the soil to block other seeds from germinating.

Whereas, the actinomycetes produce a chemical called geosmin.

Now when rain hits the ground, it brings up
the oils and geosmin which then mix with air.

The combination of this geosmin along with the plant oils form the smell which we receive after the rain.

It happens because of blood vessels in our
eyes and pupil.

Pupil is a small opening whose size is adjusted by the circular muscle called iris.

In bright light, the iris contracts making
the pupil smaller.

Thus allowing less light to enter into our eyes.

In dark, the iris relaxes making the pupil
larger, thus allowing more light to enter.

Also exposing the blood vessels in our
eyes.

Hence, when we take a photo in such a dark environment.

The flash of light from the camera floods into our eyes at once.

Some of this light gets reflected from the blood vessels onto the camera before our iris can contract.

So that we look more experienced and intelligent.

Smoking makes people look old because things like cigarettes contain nicotine.

Nicotine is a vasoconstrictor which means
it narrows our blood vessels.

When the blood supply is restricted, our cells don't get the required oxygen and nutrients.

As a result, our skin becomes dry and discoloured.

In addition to this, the collagen and elastin
fibers which keep our skin firm and elastic.

Begin to break down much faster, leading to saggy and wrinkled skin.

Also, when we smoke, we purse our lips and squint our eyes.

Regularly repeating these actions may also cause wrinkles on our lips and around our eyes.

In this way, smoking makes our skin dry, saggy and wrinkled, thus making us look old.