The surprising reason you feel awful when you're sick - Marco A. Sotomayor
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0:08 - 0:12It starts with a tickle in your throat
that becomes a cough. -
0:12 - 0:14Your muscles begin to ache,
-
0:14 - 0:16you grow irritable,
-
0:16 - 0:18and you lose your appetite.
-
0:18 - 0:21It's official: you've got the flu.
-
0:21 - 0:24It's logical to assume that this
miserable medley of symptoms -
0:24 - 0:27is the result of the infection
coursing through your body, -
0:27 - 0:29but is that really the case?
-
0:29 - 0:32What's actually making you feel sick?
-
0:32 - 0:37What if your body itself
was driving this vicious onslaught? -
0:37 - 0:42You first get ill when a pathogen
like the flu virus gets into your system, -
0:42 - 0:45infecting and killing your cells.
-
0:45 - 0:47But this unwelcome intrusion
has another effect: -
0:47 - 0:51it alerts your body's immune system
to your plight. -
0:51 - 0:57As soon as it becomes aware of infection,
your body leaps to your defense. -
0:57 - 1:01Cells called macrophages charge in
as the first line of attack, -
1:01 - 1:05searching for and destroying the viruses
and infected cells. -
1:05 - 1:11Afterwards, the macrophages release
protein molecules called cytokines -
1:11 - 1:12whose job is to recruit
-
1:12 - 1:17and organize more virus-busting cells
from your immune system. -
1:17 - 1:19If this coordinated effort
is strong enough, -
1:19 - 1:23it'll wipe out the infection
before you even notice it. -
1:23 - 1:27But that's just your body setting
the scene for some real action. -
1:27 - 1:30In some cases, viruses spread further,
-
1:30 - 1:33even into the blood and vital organs.
-
1:33 - 1:35To avoid this sometimes dangerous fate,
-
1:35 - 1:38your immune system must launch
a stronger attack, -
1:38 - 1:41coordinating its activity with the brain.
-
1:41 - 1:44That's where those unpleasant symptoms
come in, -
1:44 - 1:46starting with the surging temperature,
-
1:46 - 1:47aches and pains,
-
1:47 - 1:48and sleepiness.
-
1:48 - 1:51So why do we experience this?
-
1:51 - 1:54When the immune system is under
serious attack, -
1:54 - 1:56it secretes more cytokines,
-
1:56 - 1:58which trigger two responses.
-
1:58 - 2:02First, the vagus nerve, which runs through
the body into the brain, -
2:02 - 2:05quickly transmits the information
to the brain stem, -
2:05 - 2:09passing near an important area
of pain processing. -
2:09 - 2:13Second, cytokines travel through
the body to the hypothalamus, -
2:13 - 2:16the part of the brain responsible
for controlling temperature, -
2:16 - 2:17thirst,
-
2:17 - 2:18hunger,
-
2:18 - 2:19and sleep,
-
2:19 - 2:21among other things.
-
2:21 - 2:22When it receives this message,
-
2:22 - 2:24the hypothalamus produces
another molecule -
2:24 - 2:29called prostaglandin E2,
which gears it up for war. -
2:29 - 2:33The hypothalamus sends signals
that instruct your muscles to contract -
2:33 - 2:36and causes a rise in body temperature.
-
2:36 - 2:37It also makes you sleepy,
-
2:37 - 2:41and you lose your appetite and thirst.
-
2:41 - 2:44But what's the point of all of these
unpleasant symptoms? -
2:44 - 2:46Well, we're not yet sure,
-
2:46 - 2:49but some theorize that they aid
in recovery. -
2:49 - 2:52The rise in temperature can slow bacteria
-
2:52 - 2:55and help your immune system
destroy pathogens. -
2:55 - 2:59Sleep lets your body channel
more energy towards fighting infection. -
2:59 - 3:03When you stop eating, your liver can
take up much of the iron in your blood, -
3:03 - 3:06and since iron is essential
for bacterial survival, -
3:06 - 3:09that effectively starves them.
-
3:09 - 3:13Your reduced thirst makes
you mildly dehydrated, -
3:13 - 3:15diminishing transmission through sneezes,
-
3:15 - 3:16coughs,
-
3:16 - 3:17vomit,
-
3:17 - 3:18or diarrhea.
-
3:18 - 3:21Though it's worth noting that if you don't
drink enough water, -
3:21 - 3:24that dehydration can become dangerous.
-
3:24 - 3:26Even the body's aches
make you more sensitive, -
3:26 - 3:30drawing attention to infected cuts
that might be worsening, -
3:30 - 3:33or even causing your condition.
-
3:33 - 3:35In addition to physical symptoms,
-
3:35 - 3:37sickness can also make you irritable,
-
3:37 - 3:38sad,
-
3:38 - 3:39and confused.
-
3:39 - 3:41That's because cytokines and prostaglandin
-
3:41 - 3:44can reach even higher structures
in your brain, -
3:44 - 3:47disrupting the activity
of neurotransmitters, -
3:47 - 3:48like glutamate,
-
3:48 - 3:49endorphins,
-
3:49 - 3:50serotonin,
-
3:50 - 3:52and dopamine.
-
3:52 - 3:56This affects areas like the limbic system,
which oversees emotions, -
3:56 - 4:01and your cerebral cortex,
which is involved in reasoning. -
4:01 - 4:03So it's actually the body's own
immune response -
4:03 - 4:08that causes much of the discomfort
you feel every time you get ill. -
4:08 - 4:11Unfortunately, it doesn't always
work perfectly. -
4:11 - 4:16Most notably, millions of people
worldwide suffer from autoimmune diseases, -
4:16 - 4:21in which the immune system treats
normal bodily cues as threats, -
4:21 - 4:24so the body attacks itself.
-
4:24 - 4:26But for the majority of the human race,
-
4:26 - 4:29millions of years of evolution
have fine-tuned the immune system -
4:29 - 4:33so that it works for,
rather than against us. -
4:33 - 4:35The symptoms of our illnesses
are annoying, -
4:35 - 4:39but collectively,
they signify an ancient process -
4:39 - 4:43that will continue barricading our bodies
against the outside world -
4:43 - 4:45for centuries to come.
- Title:
- The surprising reason you feel awful when you're sick - Marco A. Sotomayor
- Speaker:
- Marco A. Sotomayor
- Description:
-
View full lesson: http://ed.ted.com/lessons/the-surprising-reason-you-feel-awful-when-you-re-sick-marco-a-sotomayor
It starts with a tickle in your throat that becomes a cough. Your muscles begin to ache, you grow irritable, and you lose your appetite. It’s official: you’ve got the flu. It’s logical to assume that this miserable medley of symptoms is the result of the infection coursing through your body — but is that really the case? Marco A. Sotomayor explains what’s actually making you feel sick.
Lesson by Marco A. Sotomayor, animation by Henrik Malmgren.
- Video Language:
- English
- Team:
- closed TED
- Project:
- TED-Ed
- Duration:
- 05:01
Jessica Ruby approved English subtitles for The surprising reason you feel awful when you're sick | ||
Jessica Ruby edited English subtitles for The surprising reason you feel awful when you're sick | ||
Jessica Ruby accepted English subtitles for The surprising reason you feel awful when you're sick | ||
Jessica Ruby edited English subtitles for The surprising reason you feel awful when you're sick | ||
Jessica Ruby edited English subtitles for The surprising reason you feel awful when you're sick | ||
Jennifer Cody edited English subtitles for The surprising reason you feel awful when you're sick | ||
Jennifer Cody edited English subtitles for The surprising reason you feel awful when you're sick |