[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:07.01,0:00:09.58,Default,,0000,0000,0000,,You're standing at \Nthe ready inside the goal
Dialogue: 0,0:00:09.58,0:00:14.23,Default,,0000,0000,0000,,when suddenly, you feel an intense itch\Non the back of your head.
Dialogue: 0,0:00:14.23,0:00:17.94,Default,,0000,0000,0000,,We've all experienced the annoyance \Nof an inconvenient itch,
Dialogue: 0,0:00:17.94,0:00:22.80,Default,,0000,0000,0000,,but have you ever pondered why\Nwe itch in the first place?
Dialogue: 0,0:00:22.80,0:00:27.63,Default,,0000,0000,0000,,The average person experiences\Ndozens of individual itches each day.
Dialogue: 0,0:00:27.63,0:00:29.82,Default,,0000,0000,0000,,They can be triggered by all sorts\Nof things,
Dialogue: 0,0:00:29.82,0:00:31.52,Default,,0000,0000,0000,,including allergic reactions,
Dialogue: 0,0:00:31.52,0:00:32.52,Default,,0000,0000,0000,,dryness,
Dialogue: 0,0:00:32.52,0:00:34.70,Default,,0000,0000,0000,,and even some diseases.
Dialogue: 0,0:00:34.70,0:00:39.33,Default,,0000,0000,0000,,And then there are the mysterious ones\Nthat pop up for no reason at all,
Dialogue: 0,0:00:39.33,0:00:41.97,Default,,0000,0000,0000,,or just from talking about itching.
Dialogue: 0,0:00:41.97,0:00:45.51,Default,,0000,0000,0000,,You're scratching your head right now,\Naren't you?
Dialogue: 0,0:00:45.51,0:00:50.06,Default,,0000,0000,0000,,Anyhow, let's take one of the most\Ncommon sources: bug bites.
Dialogue: 0,0:00:50.06,0:00:51.43,Default,,0000,0000,0000,,When a mosquito bites you,
Dialogue: 0,0:00:51.43,0:00:55.80,Default,,0000,0000,0000,,it releases a compound into your body\Ncalled an anticoagulant
Dialogue: 0,0:00:55.80,0:00:58.53,Default,,0000,0000,0000,,that prevents your blood from clotting.
Dialogue: 0,0:00:58.53,0:01:01.26,Default,,0000,0000,0000,,That compound, \Nwhich we're mildly allergic to,
Dialogue: 0,0:01:01.26,0:01:03.88,Default,,0000,0000,0000,,triggers the release of histamine,
Dialogue: 0,0:01:03.88,0:01:06.98,Default,,0000,0000,0000,,a chemical that makes \Nour capillaries swell.
Dialogue: 0,0:01:06.98,0:01:08.94,Default,,0000,0000,0000,,This enables increased blood flow,
Dialogue: 0,0:01:08.94,0:01:11.96,Default,,0000,0000,0000,,which helpfully accelerates \Nthe body's immune response
Dialogue: 0,0:01:11.96,0:01:14.20,Default,,0000,0000,0000,,to this perceived threat.
Dialogue: 0,0:01:14.20,0:01:15.85,Default,,0000,0000,0000,,That explains the swelling,
Dialogue: 0,0:01:15.85,0:01:19.78,Default,,0000,0000,0000,,and it's the same reason pollen\Ncan make your eyes puff up.
Dialogue: 0,0:01:19.78,0:01:23.54,Default,,0000,0000,0000,,Histamine also activates the nerves\Ninvolved in itching,
Dialogue: 0,0:01:23.54,0:01:27.85,Default,,0000,0000,0000,,which is why bug bites make you scratch.
Dialogue: 0,0:01:27.85,0:01:31.70,Default,,0000,0000,0000,,But the itchy sensation itself\Nisn't yet fully understood.
Dialogue: 0,0:01:31.70,0:01:33.43,Default,,0000,0000,0000,,In fact, much of what we do know
Dialogue: 0,0:01:33.43,0:01:38.16,Default,,0000,0000,0000,,comes from studying \Nthe mechanics of itching in mice.
Dialogue: 0,0:01:38.16,0:01:41.06,Default,,0000,0000,0000,,Researchers have discovered that\Nitch signals in their skin
Dialogue: 0,0:01:41.06,0:01:47.04,Default,,0000,0000,0000,,are transmitted via a subclass of\Nthe nerves that are associated with pain.
Dialogue: 0,0:01:47.04,0:01:52.68,Default,,0000,0000,0000,,These dedicated nerves produce a molecule\Ncalled natriuretic polypetide B,
Dialogue: 0,0:01:52.68,0:01:56.90,Default,,0000,0000,0000,,which triggers a signal that's carried\Nup the spinal cord to the brain,
Dialogue: 0,0:01:56.90,0:02:00.76,Default,,0000,0000,0000,,where it creates the feeling of an itch.
Dialogue: 0,0:02:00.76,0:02:04.39,Default,,0000,0000,0000,,When we scratch, the action of our\Nfingernails on the skin
Dialogue: 0,0:02:04.39,0:02:10.14,Default,,0000,0000,0000,,causes a low level pain signal\Nthat overrides the itching sensation.
Dialogue: 0,0:02:10.14,0:02:15.43,Default,,0000,0000,0000,,It's almost like a distraction,\Nwhich creates the sensation of relief.
Dialogue: 0,0:02:15.43,0:02:19.70,Default,,0000,0000,0000,,But is there actually an evolutionary\Npurpose to the itch,
Dialogue: 0,0:02:19.70,0:02:23.18,Default,,0000,0000,0000,,or is it simply there to annoy us?
Dialogue: 0,0:02:23.18,0:02:28.25,Default,,0000,0000,0000,,The leading theory is that our skin\Nhas evolved to be acutely aware of touch
Dialogue: 0,0:02:28.25,0:02:32.43,Default,,0000,0000,0000,,so that we're equipped to deal with risks\Nfrom the outside world.
Dialogue: 0,0:02:32.43,0:02:33.35,Default,,0000,0000,0000,,Think about it.
Dialogue: 0,0:02:33.35,0:02:37.18,Default,,0000,0000,0000,,Our automatic scratching response\Nwould dislodge anything harmful
Dialogue: 0,0:02:37.18,0:02:40.09,Default,,0000,0000,0000,,that's potentially lurking on our skin,
Dialogue: 0,0:02:40.09,0:02:41.46,Default,,0000,0000,0000,,like a harmful sting,
Dialogue: 0,0:02:41.46,0:02:42.78,Default,,0000,0000,0000,,a biting insect,
Dialogue: 0,0:02:42.78,0:02:45.83,Default,,0000,0000,0000,,or the tendrils of a poisonous plant.
Dialogue: 0,0:02:45.83,0:02:49.43,Default,,0000,0000,0000,,This might explain why we don't\Nfeel itching inside our bodies,
Dialogue: 0,0:02:49.43,0:02:50.91,Default,,0000,0000,0000,,like in our intestines,
Dialogue: 0,0:02:50.91,0:02:53.45,Default,,0000,0000,0000,,which is safe from these external threats,
Dialogue: 0,0:02:53.45,0:02:57.39,Default,,0000,0000,0000,,though imagine how \Nmaddening that would be.
Dialogue: 0,0:02:57.39,0:03:01.12,Default,,0000,0000,0000,,In some people, glitches in the pathways\Nresponsible for all of this
Dialogue: 0,0:03:01.12,0:03:06.07,Default,,0000,0000,0000,,can cause excessive itching\Nthat can actually harm their health.
Dialogue: 0,0:03:06.07,0:03:11.46,Default,,0000,0000,0000,,One extreme example is a psychological\Ncondition called delusory parasitosis
Dialogue: 0,0:03:11.46,0:03:15.51,Default,,0000,0000,0000,,where people believe their bodies\Nare infested with mites or fleas
Dialogue: 0,0:03:15.51,0:03:18.47,Default,,0000,0000,0000,,scurrying over and under their skin,
Dialogue: 0,0:03:18.47,0:03:22.31,Default,,0000,0000,0000,,making them itch incessantly.
Dialogue: 0,0:03:22.31,0:03:24.42,Default,,0000,0000,0000,,Another phenomenon \Ncalled phantom itching
Dialogue: 0,0:03:24.42,0:03:27.58,Default,,0000,0000,0000,,can occur in patients \Nwho've had amputations.
Dialogue: 0,0:03:27.58,0:03:31.87,Default,,0000,0000,0000,,Because this injury has \Nso severely damaged the nervous system,
Dialogue: 0,0:03:31.87,0:03:35.00,Default,,0000,0000,0000,,it confuses the body's normal \Nnerve signaling
Dialogue: 0,0:03:35.00,0:03:40.43,Default,,0000,0000,0000,,and creates sensations in limbs\Nthat are no longer there.
Dialogue: 0,0:03:40.43,0:03:45.06,Default,,0000,0000,0000,,Doctors are now finding ways\Nto treat these itching anomalies.
Dialogue: 0,0:03:45.06,0:03:49.23,Default,,0000,0000,0000,,In amputees, mirrors are used to reflect\Nthe remaining limb,
Dialogue: 0,0:03:49.23,0:03:51.60,Default,,0000,0000,0000,,which the patient scratches.
Dialogue: 0,0:03:51.60,0:03:53.96,Default,,0000,0000,0000,,That creates an illusion \Nthat tricks the brain
Dialogue: 0,0:03:53.96,0:03:58.61,Default,,0000,0000,0000,,into thinking the imaginary \Nitch has been satisfied.
Dialogue: 0,0:03:58.61,0:04:02.18,Default,,0000,0000,0000,,Oddly enough, that actually works.
Dialogue: 0,0:04:02.18,0:04:05.83,Default,,0000,0000,0000,,Researchers are also searching\Nfor the genes involved in itching
Dialogue: 0,0:04:05.83,0:04:09.32,Default,,0000,0000,0000,,and developing treatments to try\Nand block the pathway of an itch
Dialogue: 0,0:04:09.32,0:04:12.00,Default,,0000,0000,0000,,in extreme cases.
Dialogue: 0,0:04:12.00,0:04:16.50,Default,,0000,0000,0000,,If having an unscratchable itch\Nfeels like your own personal hell,
Dialogue: 0,0:04:16.50,0:04:19.00,Default,,0000,0000,0000,,Dante agreed.
Dialogue: 0,0:04:19.00,0:04:21.44,Default,,0000,0000,0000,,The Italian poet wrote about\Na section of hell
Dialogue: 0,0:04:21.44,0:04:28.66,Default,,0000,0000,0000,,where people were punished by being\Nleft in pits to itch for all eternity.