B2 中高級 14423 分類 收藏
Our story is about a girl named Iris.
Iris is very sensitive.
So much that she is always in tears.
She cries when she's sad,
when she's happy,
and even tears up when things just get to her.
She has special lacrimal glands to make new tears
and special tubes, called lacrimal puncta,
to drain old ones away.
And she cries so much that she goes through
ten ounces of tears per day,
thirty gallons a year!
In fact, if you look closely,
you'll see that she's crying a little bit all the time.
The basal tears that Iris constantly produces
form a thin coating of three layers
that cover her and keep dirt and debris away.
Right next to Iris is the mucus layer,
which keeps the whole thing fastened to her.
On top of it is the aqueous layer,
which keeps Iris hydrated,
repels invasive bacteria,
and protects her skin, or cornea, from damage.
And, finally, there is the lipid layer,
an oily outer film that keeps the surface smooth
for Iris to see through,
and prevents the other layers from evaporating.
Normally, Iris goes about her day
without really noticing the basal tears
doing their thing.
That's kind of their whole point.
But one day, she meets a girl named Onion.
Iris is immediately smitten.
Onion looks gorgeous in her bright purple jacket,
and she smells terrific.
So, Iris invites Onion to her house for dinner,
but when she comes in and takes off her jacket,
something terrible happens.
You see, when Onion's jacket is removed,
a chemical reaction happens,
converting the sulfoxides that make her smell so great
into sulfenic acid,
which then becomes a nasty substance with a long name:
syn-Propanethial S-oxide.
The gas stings Iris,
and suddenenly, she can't help it,
she starts weeping uncontrollably.
These reflex tears are different from the basal tears that Iris is used to.
Because they're designed
to wash away harmful substances, or particles,
they're released in much larger amounts,
and their aqueous layer contains more antibodies
to stop any microorganisms that may be trying to get in, as well.
Both Iris and Onion are devastated.
They know they can't continue their relationship
if Iris is going to hurt and cry
every time Onion takes off her jacket.
So, they decide to break up.
As Onion walks out the door,
Iris stops crying.
And immediately starts again.
Only now, she's not crying reflex tears
but emotional tears.
When someone is either too sad or too happy,
it feels like a loss of control,
which can be dangerous.
So, emotional tears are sent in
to stabilize the mood as quickly as possible,
along with other physical reactions,
such as an increased heart rate
and slower breathing.
But scientists still aren't sure
exactly how or why the tears themselves are helpful.
They may be a social mechanism
to elicit sympathy or show submission.
But some studies have also found
that emotional tears contain higher levels
of stress hormones,
such as ACTH and enkephalin,
an endorphin and natural pain killer.
In this case, emotional tears are also directly calming Iris down,
as well as signaling her emotional state to others.
Sorry things didn't work out with Onion, Iris,
but don't worry.
As long as you have all three kinds of tears
working to keep you balanced and healthy,
it will get better.
You'll see.



【TED-Ed】我們為何會哭? 三種不同的眼淚 (Why do we cry? The three types of tears - Alex Gendler)

14423 分類 收藏
阿多賓 發佈於 2014 年 3 月 12 日    謝明廷 翻譯    Mandy Lin 審核
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