Why do we cry? The three types of tears - Alex Gendler
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0:06 - 0:10Our story is about a girl named Iris.
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0:10 - 0:13Iris is very sensitive.
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0:13 - 0:17So much that she is always in tears.
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0:17 - 0:20She cries when she's sad,
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0:20 - 0:23when she's happy,
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0:23 - 0:28and even tears up when things just get to her.
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0:28 - 0:31She has special lacrimal glands to make new tears
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0:31 - 0:34and special tubes, called lacrimal puncta,
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0:34 - 0:37to drain old ones away.
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0:37 - 0:39And she cries so much that she goes through
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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 - 0:50you'll see that she's crying a little bit all the time.
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0:50 - 0:53The basal tears that Iris constantly produces
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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.
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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.
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1:04 - 1:06On top of it is the aqueous layer,
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1:06 - 1:08which keeps Iris hydrated,
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1:08 - 1:09repels invasive bacteria,
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1:09 - 1:13and protects her skin, or cornea, from damage.
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1:13 - 1:16And, finally, there is the lipid layer,
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1:16 - 1:18an oily outer film that keeps the surface smooth
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1:18 - 1:20for Iris to see through,
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1:20 - 1:23and prevents the other layers from evaporating.
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1:23 - 1:25Normally, Iris goes about her day
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1:25 - 1:27without really noticing the basal tears
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1:27 - 1:28doing their thing.
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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 - 1:38Onion looks gorgeous in her bright purple jacket,
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1:38 - 1:40and she smells terrific.
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1:40 - 1:42So, Iris invites Onion to her house for dinner,
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1:42 - 1:45but when she comes in and takes off her jacket,
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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
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1:55 - 1:57into sulfenic acid,
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1:57 - 2:01which then becomes a nasty substance with a long name:
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2:01 - 2:04syn-Propanethial S-oxide.
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2:04 - 2:06The gas stings Iris,
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2:06 - 2:08and suddenenly, she can't help it,
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2:08 - 2:10she starts weeping uncontrollably.
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2:10 - 2:13These reflex tears are different from the basal tears
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2:13 - 2:15that 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,
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2:18 - 2:21they're released in much larger amounts,
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2:21 - 2:24and their aqueous layer contains more antibodies
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2:24 - 2:28to stop any microorganisms that may be trying to get in, as well.
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2:28 - 2:31Both Iris and Onion are devastated.
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2:31 - 2:33They know they can't continue their relationship
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2:33 - 2:35if Iris is going to hurt and cry
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2:35 - 2:38every time Onion takes off her jacket.
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2:38 - 2:40So, they decide to break up.
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2:40 - 2:42As Onion walks out the door,
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2:42 - 2:43Iris stops crying.
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2:43 - 2:45And immediately starts again.
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2:45 - 2:47Only now, she's not crying reflex tears
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2:47 - 2:50but emotional tears.
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2:50 - 2:53When someone is either too sad or too happy,
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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 - 2:57So, emotional tears are sent in
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2:57 - 2:59to stabilize the mood
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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 - 3:04such as an increased heart rate
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3:04 - 3:06and slower breathing.
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3:06 - 3:08But scientists still aren't sure
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3:08 - 3:12exactly how or why the tears themselves are helpful.
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3:12 - 3:13They may be a social mechanism
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3:13 - 3:16to elicit sympathy or show submission.
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3:16 - 3:18But some studies have also found
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3:18 - 3:20that emotional tears contain higher levels
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3:20 - 3:21of stress hormones,
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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,
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3:30 - 3:33as well as signaling her emotional state to others.
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3:33 - 3:36Sorry things didn't work out with Onion, Iris,
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3:36 - 3:37but don't worry.
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3:37 - 3:39As long as you have all three kinds of tears
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3:39 - 3:41working to keep you balanced and healthy,
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3:41 - 3:42it will get better.
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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.