Why do we cry? The three types of tears - Alex Gendler
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0:07 - 0:10Our story is about a girl named Iris.
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0:10 - 0:12Iris is very sensitive.
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0:12 - 0:13(Bird cawing)
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0:13 - 0:16So much that she is always in tears.
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0:17 - 0:19She cries when she's sad,
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0:20 - 0:22when she's happy,
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0:22 - 0:23(Godzilla roars)
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0:23 - 0:26and even tears up
when things just get to her. -
0:28 - 0:31She has special lacrimal glands
to make new tears -
0:31 - 0:34and special tubes, called lacrimal puncta,
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0:34 - 0:35to drain old ones away.
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0:37 - 0:39And she cries so much
that she goes through -
0:39 - 0:41ten ounces of tears per day,
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0:41 - 0:43thirty gallons a year!
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0:43 - 0:45In fact, if you look closely,
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0:45 - 0:49you'll see that she's crying
a little bit all the time. -
0:50 - 0:53The basal tears that Iris
constantly produces -
0:53 - 0:55form a thin coating of three layers
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0:55 - 0:58that cover her and keep
dirt and debris away. -
0:58 - 1:01Right next to Iris is the mucus layer,
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1:01 - 1:04which keeps the whole
thing fastened to her. -
1:04 - 1:06On top of it is the aqueous layer,
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1:06 - 1:09which keeps Iris hydrated,
repels invasive bacteria, -
1:09 - 1:12and protects her skin,
or cornea, from damage. -
1:13 - 1:16And, finally, there is the lipid layer,
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1:16 - 1:19an oily outer film that keeps
the surface smooth -
1:19 - 1:20for Iris to see through,
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1:20 - 1:22and prevents the other
layers from evaporating. -
1:23 - 1:25Normally, Iris goes about her day
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1:25 - 1:28without really noticing
the basal tears doing their thing. -
1:28 - 1:30That's kind of their whole point.
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1:30 - 1:33But one day, she meets a girl named Onion.
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1:33 - 1:35Iris is immediately smitten.
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1:35 - 1:37Onion looks gorgeous in her
bright purple jacket, -
1:37 - 1:39and she smells terrific.
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1:40 - 1:42So, Iris invites Onion
to her house for dinner. -
1:43 - 1:45But when she comes in
and takes off her jacket, -
1:45 - 1:47something terrible happens.
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1:47 - 1:50You see, when Onion's jacket is removed,
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1:50 - 1:51a chemical reaction happens,
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1:51 - 1:55converting the sulfoxides
that make her smell so great -
1:55 - 1:57into sulfenic acid,
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1:57 - 2:00which then becomes a nasty
substance with a long name: -
2:01 - 2:03syn-Propanethial S-oxide.
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2:04 - 2:08The gas stings Iris,
and suddenly, she can't help it, -
2:08 - 2:09she starts weeping uncontrollably.
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2:10 - 2:13These reflex tears are different
from the basal tears -
2:13 - 2:14that Iris is used to.
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2:15 - 2:16Because they're designed
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2:16 - 2:18to wash away harmful
substances, or particles, -
2:19 - 2:21they're released in much larger amounts,
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2:21 - 2:24and their aqueous layer
contains more antibodies -
2:24 - 2:27to stop any microorganisms
that may be trying to get in, as well. -
2:28 - 2:30Both Iris and Onion are devastated.
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2:31 - 2:33They know they can't continue
their relationship -
2:33 - 2:38if Iris is going to hurt and cry
every time Onion takes off her jacket. -
2:38 - 2:39So, they decide to break up.
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2:40 - 2:42As Onion walks out the door,
Iris stops crying. -
2:43 - 2:44And immediately starts again.
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2:45 - 2:49Only now, she's not crying
reflex tears but emotional tears. -
2:50 - 2:53When someone is either
too sad or too happy, -
2:53 - 2:54it feels like a loss of control,
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2:54 - 2:56which can be dangerous.
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2:56 - 2:59So, emotional tears are sent in
to stabilize the mood -
2:59 - 3:01as quickly as possible,
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3:01 - 3:03along with other physical reactions,
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3:03 - 3:06such as an increased heart rate
and slower breathing. -
3:06 - 3:08But scientists still aren't sure
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3:08 - 3:11exactly how or why the tears
themselves are helpful. -
3:11 - 3:15They may be a social mechanism
to elicit sympathy or show submission. -
3:16 - 3:18But some studies have also found
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3:18 - 3:21that emotional tears contain
higher levels of stress hormones, -
3:21 - 3:24such as ACTH and enkephalin,
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3:24 - 3:27an endorphin and natural pain killer.
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3:27 - 3:30In this case, emotional tears
are also directly calming Iris down, -
3:30 - 3:33as well as signaling
her emotional state to others. -
3:34 - 3:36Sorry things didn't work out
with Onion, Iris, -
3:36 - 3:37but don't worry.
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3:37 - 3:39As long as you have
all three kinds of tears -
3:39 - 3:42working to keep you balanced
and healthy, it will get better. -
3:42 - 3:43You'll see.
- Title:
- Why do we cry? The three types of tears - Alex Gendler
- Speaker:
- Alex Gendler
- Description:
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View full lesson: http://ed.ted.com/lessons/why-do-we-cry-the-three-types-of-tears-alex-gendler
Whether we cry during a sad movie, while chopping onions, or completely involuntarily, our eyes are constantly producing tears. Alex Gendler tracks a particularly watery day in the life of Iris (the iris) as she cycles through basal, reflex and emotional tears.
Lesson by Alex Gendler, animation by The Moving Company Animation Studio.
- Video Language:
- English
- Team:
- closed TED
- Project:
- TED-Ed
- Duration:
- 03:59
Krystian Aparta edited English subtitles for Why do we cry? The three types of tears | ||
Krystian Aparta commented on English subtitles for Why do we cry? The three types of tears | ||
Caroline Cristal edited English subtitles for Why do we cry? The three types of tears | ||
Caroline Cristal approved English subtitles for Why do we cry? The three types of tears | ||
Caroline Cristal accepted English subtitles for Why do we cry? The three types of tears | ||
Caroline Cristal edited English subtitles for Why do we cry? The three types of tears | ||
Caroline Cristal edited English subtitles for Why do we cry? The three types of tears | ||
Jessica Ruby edited English subtitles for Why do we cry? The three types of tears |
Krystian Aparta
The English transcript was updated on 2/13/2015.