Vision: Crash Course Anatomy & Physiology #18

[@itsjusttravis692]

I remember watching this video SO MANY TIMES for my high school biology tests because I couldn't get it. Now, I'm about to graduate university and start practicing as an optometrist. Thanks Hank 😬

[@lin80085]

This is so cute! Congrats! PS If you want some easy to digest eyeball material, I highly suggest anything by Tim Root.

[@9Epicman]

Im using my eyes to learn about eyes

[@fortimTT]

that's deep, man

[@emilytheweirdo4752]

And your ears to hear Hank talking

[@cheesypizzajokes]

i can respect that

[@MrSnuggelsworth]

Funny how the brain has defined itself as the most particularly superior to other forms of life..

[@amirabawa]

😂😂

[@llawliet2310]

More info (not that anyone asked but here I go) - there are more cones packed in the centre of the retina known s as the fovea. Each cone has a small receptive field (on centre off surround); conversely there's more rods scattered throughout the periphery with larger receptive fields - due to the small receptive field, each cone can pick up information in their reference in great detail (high visual acuity) because each is focused on a small part of the visual field. Vice versa for Rods which is why they are better suited for movement and black and white imagery - our visual field is represented as an image on the back of our retina due to retinotopic organization; this information is not altered - cones attach to parvocellular retinal ganglion cells while rods attach to magnocellular retinal ganglion cells - the optic nerve leaves the retina and travels to the thalamus which is responsible for relaying all incoming sensory information aside from olfaction. Visual information is relayed through the Lateral Geniculate Nucleus of the thalamus to PVC (primary visual cortex) of the occipital lobe - magnocellular pathways in the LGN are relayed through layers 1&2 of the LGN while parvocellular pathways through 3,4,5&6 - when this information reaches the occipital lobe, magnocellular pathways are sent through the thick stripes of the striated cortex (through indirect and direct pathways) - parvocellular pathways are sent through interstripes and thin stripes (visual acuity) of the striated cortex of the occipital lobe - when we see an object we are familiar with, two general things are happening: the occipital lobe sends information through the dorsal and ventral streams to go to the parietal and temporal lobes respectively - once the dorsal pathway reaches the posterior parietal cortex (PPC) this is where spatial recognition happens (exactly where in the visual field the object of focus is) - when the ventral pathway reaches the Inferior temporal gurus (IT) it's responsible for object recognition- what exactly it is what we are looking at - there's more to this than just what I've wrote but it's an extremely interesting sense to study; also easier to study in contrast to cognition because vision is localized to select discrete areas of the brain

[@alkaveenus7883]

Thank you so much for these educative points.

[@aasthasharma3820]

Hank: that you don't want to google Me: IMMEDIATELY googles it extremely disgusted goes back to video Hank: I'll just sit here and wait for you to google it

[@mytaeneedssomesuga9130]

aastha sharma same here

[@sui5000]

aastha sharma so what is it? I'm to afraid to search it 😰

[@isiomam8945]

same when he said that i went googled it but it gross

[@bonnie52229]

I googled this, and I expected worse.

[@jacoblaughslel4765]

SAME!

[@Moontigerlily1]

hey guys you know what would make your videos even better?! if you could include the script in the video description, TO STUDY FROM! That would be amazing. LOOOOVE your videos

[@user-be3hp7he9y]

This is late but if you open KZbin from a computer, you can open the script! Click the three dots below the video and then click "open transcript" :)

[@Mai-tu2cb]

It would be nice, but i wouldn't demand tho 😂 I rewriting everything he says in my notes and its effective in reviewing👌

[@jaymo142]

Came off a bit rude...

[@danielreinaga1727]

mercedez tinney ID love to study you

[@letssacrificetobymarshall1145]

Subtitles

[@DuranmanX]

I didn't see the flag on the white screen, does that mean I'm unpatriotic?

[@therealandrewlund]

***** technically, I guess it just means that our cones are in great physical shape and don't tire easily..

[@grimreefer4366]

***** You moved your eyes I'd guess. I'm a little bit drunk, and me eyes kept shifting around the image. I've seen it before though. You really have to stare at it, not just casually watch it.

[@komali100]

***** No. I think what might have happened is your eyes were still getting light from other sources. Did you by chance watch this video in a well lit room? The effect of the illusion is at its greatest if you look at it fullscreen, with your computer's screen at the brightest level, in a dark room.

[@AzureKite]

komali100 Not only the effect of the illusion is greatest but you'll also go blind a few years earlier if you do too much of that.

[@DuranmanX]

komali100 well I've done all that, even without getting a bit of sleep, and I still couldn't see it could it be because I wear glasses?

[@chrisquisha2429]

I'm a nurse and even I started feeling woozy at those globe luxation pics omg... anyone who isn't in a medical profession, looked it up, and endured the images has my IMMEDIATE respect! Next time you're in emerg let your nurse know of your accomplishment and you'll have a new best friend

[@cakevictim]

I work in surgery- didn't google, don't like getting into globes!

[@conandenz8413]

It's not that bad.

[@IIIUTUBEIII]

I resisted the temptation I didn't google it.

[@oldebricklighting1793]

boobs

[@Ava-ks4yn]

i started to but didnt click on images even though i *really really* wanted to

[@subhashreepanda4189]

I am honestly proud of u U just saved urself from a week filled with trauma

[@Cheese-hi5ix]

Ava Grace do. Not. Click. Images.

[@NeleDeGersem]

me too but i was NOT tempted

[@ghostiegoobie]

I have a psychology exam in two days. Praise this video for making studying pages upon pages of textbook info entertaining and amusing.

[@mjocosta8275]

now i will hold my eyes every time i sneeze for my entire life XD

[@Peanutker]

Hank:You really do not wanna goggle it Me:* Immediately goggles it and cry’s because of the images* Hank:I will just wait for you to goggle it Me:*still crying*

[@christianjames6256]

You literally came back to rods & cones in a minute after you mentioned it (5:13 to 6:13)

[@aasthasharma3820]

5 13 is my birthday

[@miss0noodle]

aastha sharma almost your day!

[@vmlynn875]

Without Crash Course, I would have failed at Anatomy. Thanks so much!! I did very well in the class!

[@fiaa.6539]

Hank: ... called Globe Luxation-- *immedately googles* *cries out in disgust and terror* *Plays video* Hank: That you really don't want to google!

[@teagan_p_999]

And then the "I'll just wait here while you google it" because we all know we will.

[@GetCraftyCrafty]

My eyes!!!

[@TriggerHappyRC1]

Googled it, looked painful but nothing special. Got me curious about some of the common causes for it. Learned that globe luxation can be caused by Grave's Ophthalmopathy which is an autoimmune disease that attacks the fat cells around the eye which swell compressing veins and stopping the drainage of fluid from the eye. Thanks Hank! Got to learn something extra.

[@Emilieeeee1]

Anyone noticed the pics are moving at 1:18?

[@yawsikakawty5871]

That was so obvious sure we did

[@alexchen6875]

yeah. It fits with what he is saying.

[@swatisingh950]

Emiliee yeh

[@thatonemajin3578]

loominati

[@harshilpatel4583]

Yes i did

[@chiedzamatowe4397]

Your lectures are full of energy and easy to follow. Thank you CrashCourse team.

[@adriandanekennym.d.1185]

0:45 yeah, that did not work so well for me. I just saw white on the white screen. but at harvard medical school we did one like this with three circles. one with red, one with green, and one with blue, and that one worked well for me.

[@IAmMrSoup]

Who is watching this for school

[@chloesimonds6510]

Globe Luxation is going to give me nightmares for the next 5 months

[@parkiratsingh4922]

THAT GUY IS INSANE! thanks man such a great video.

[@Buddyb309]

I GOOGLED IT!!! OH GOD WHY?! WHY DID I GOOGLE IT?!!

[@jeffct87]

I can't keep recklessly googling terms I don't know when I already can't sleep

[@Cami96]

It's not that bad...

[@Cami96]

***** I think there's so much worse stuff on the internet... try googling trypophobia

[@jeffct87]

***** and you try googling blue waffle.

[@Cami96]

thanks for supporting my point, now excuse me while I puke

[@larinaboydrn2449]

As an online AP student for nursing pre-reqs you sure made learning and getting to the point so easy! Yes.. I googled it. ugh. eww. lol Next quarter I'll be doing APII online and using you for reference. Thank you! :)

[@palakmehta365]

This channel came like a blessing in my life

[@futhark3]

A couple of months ago I visited Aarhus in Denmark and visited their art museum ARoS. Therre's an installation on top of the museum called "My Rainbow Panorama" by Ólafur Elíasson, where you can look over the city from glass of different colors. Being in there is a perfect example of how your cones are desensitized when overstimulated - If you look at the view from the red part for a while, it looks totally normal, but looking at your phone all the white letters are bright turquoise. Cracks in the glass also show how the colors are off in the "real world" after getting used to the colored version. It is totally confusing and gave me a headache after a while, but so insteresting!

[@TwoStepILY]

Today is my anp final, going in with an 85% just wanted to say thanks hank and here’s hoping I pass!!

[@chasebaldwin7801]

you should do a Crash Course on Microbiology. This is a very good outline for A&P which has helped me alot in my course!

[@dominiqueguzman1447]

I would just like to say I’ve learned more from crash course than I have from my A&P teacher all semester 🥹❤

[@ernitahunter6084]

I am a nursing student, when i watch the videos i have my biology book with me while watching. So far, everything in the videos are the same with my anatomy and physiology book. Thank You . .

[@kayleighfredericks5495]

Here before my biological psychology exam. Thanks Hank (or tHANKs!)

[@syadrinaparamita]

Kayleigh Fredericks omg same

[@fatherofwar1203]

1:17 Anybody else notice the background photos are moving?

[@Richard_is_cool]

No

[@maeen..]

Oop

[@PER2008]

THANK YOU SO MUCH for these! I am currently taking an A&P course online and your videos really help tie everything together for me. Keep up the great work. I really appreciate it.

[@Tonydaling]

Now every time before I sneeze, I will become very afraid. BTW I googled it.

[@d̈̇̃r̈̇̃]

UberGamingHD In allergic to Grass 😭 It's really hard . I feel ya.

[@carni3665]

I always try to keep my eyes open when I sneeze. Now I'm going to do otherwise.

[@minaghoshdastidar1981]

Me too 😏😏

[@otogigulis7260]

If everything is ok your eyelids will always close when sneezing so you wont damage your eyes.

[@zekeboy24]

This was probably the most interesting of the first 18 A & P videos so far! Amazing stuff, our vision.

[@jj-wz1im]

Great work... it's been two years since this was published and it is still helping people

[@mongolianpearlove]

Thank you so much for this simple and fun breakdown of vision. So helpful in studying anatomy and physiology!

[@farahm1469]

Haha never googled something faster. You got me Hank. That is fascinating stuff

[@AngelValis]

I have Ocular Albinism (at least a minor form of it because I don't present all of the symptoms listed in the wiki page, but that's what my eye doctor called it *shrugs*), so my retina doesn't contain enough pigment to completely stop light from bouncing around when it enters my eyes. As a result, even with brand-new glasses, there's usually a slight blur to the edges of things.

[@Red-ci3te]

Man I have an anatomy and physiology midterm and your videos have helped SO much.

[@aubreybanguis3616]

I always watch crash course before starting a new chapter to give me a general overview :) Thanks crash course!

[@ILoveAlice1918]

After two lectures and two books I finally understood stuff thanks to this video! Thank you!

[@geniusmp2001]

Something was bugging me about the graphic showing the cells in the retina. It took me awhile to realize what it was, but I figured it out. The photoreceptors are behind the neurons. And as soon as I realized that that was bugging me, I remembered that it's not wrong. That's actually where the cells are in the retina. Light has to go through the neurons and blood vessels to get to the photoreceptors. And the neurons have to punch a hole through the retina to get the optic nerve back to your brain, giving you a blind spot. It bothered me not because you got it wrong, but because that's a stupid way to build an eye. Cephalopods do it the other way around, because their eyes developed from the skin inward, instead of from the brain outward like vertebrates. Evolutionary baggage is everywhere.

[@S23K]

Matthew Prorok I had the same thoughts, in fact I'm not even done with the video, I had to check the comments to make sure it wasn't a mistake.:P

[@XxSeedOfEvilxX]

Matthew Prorok If only the eye was intelligently designed...

[@cuckoophendula8211]

Matthew Prorok I remember having that same thought when studying for a med school exam many years ago.

[@IMadeOfClay]

Cuckoo Phendula I remember thinking that was a stupid design too but I came across this a few months ago: m.bbc.co.uk/news/science-environment-31775458

[@ConradJD777]

+Matthew Prorok Ha look, all the people ready to hate on creationists when they don't realize that if blood vessels weren't in front of our eyes the radiation from the sun would burn through our rods and cones and we would be blind in a week.

[@KevinHosley]

3:55 I've done more than just scratch my cornea. I once had my cornea completely taken out. It took weeks for me to not be light sensitive in that eye. Luckily, I didn't lose my vision. I don't wish my injury upon anyone.

[@jenryann8183]

When Hank said: "We are going to mess with you brain." , I remembered Jason Silva and Brain Games lol hahahaha.

[@madisonkrawczyk7225]

I absolutely HATED doing the visual pathway in class, this just made it so much easier to understand I friggen love hank

[@91mezz]

Dear Hank and Crash Course, Thank you, THANK YOU, THANK YOU, THANK YOU, THANK YOU! Did I mention thank you? Seriously, your videos on anatomy and physiology have made my bio med subject way more interesting and understandable.

[@daffenieru2867]

thank you so much !! you spend a great 10 mins explaining eye function and structure in which my lecturers spend 2 hour on these .....

[@crashcourse]

Pssst... we made flashcards to help you review the content in this episode! Find them on the free Crash Course App! Download it here for Apple Devices: apple.co/3d4eyZo Download it here for Android Devices: bit.ly/2SrDulJ

[@ahcokris]

I don't want my eyes to get tired, so I don't look at the screen all through each episode. I like this cousre since i'm a "nurse" =)

[@naomigodwin865]

Hi, I'm training to be a nurse and I use Crash Course possibly more than I should admit to my lecturers, I was wondering if you could please do one on enzymes and catalyst reactions? also, thanks for saving my ass on my last assignment, I got a distinction thanks to Crash Course!

[@snkit3436]

B52 2:38 3:38 B53 0:54 1:41 5:42 6:12 7:40

[@TaiChiKnees]

Oh yay! My favorite body part! Great episode!!! Also, I have to add that when I was in training, I had a very nice patient who had very shallow orbits and I was examining his retina with a special lens that sat right on his cornea. When I was finished looking and moved to pull off the special examining lens, it had generated a little suction and pulled his globe forward and his lids drew back past his eye's equator... and wow. I knew it might happen, and knew how to fix it, and had pulled many eyes forward in surgical procedures, and completely understood there was no way possible that it would fall out like in a horror movie... but it still startled the hell out of me. It evidently happened occasionally to this patient due to his shallow orbits and he just laughed at my reaction. :-)

[@v.dargain1678]

Love it bro . What you see is definitely what you get . So don't take it for granted . Got it !

[@OrionFyre]

"Which you REALLY do not want to google." I start moving the mouse to hit the pause button "...I'll just sit here while you google it." 'Thanks Hank. be right back'

[@dulcimerrafi]

I once partook in a lab exercise in college where I was asked to sit still and keep my focus forward. Another student would slowly pass a piece of colored paper into my field of vision and I had to say when I perceived the presence of the paper and when I could definitively say what color the paper was. There was a fleeting moment when I could see the paper out of the corner of my eye, but I couldn't for the life of me tell what color it was. It was a freaky experience.

[@sharonarruda2518]

These videos are helping me so much with my biology course! I wish I discovered them months ago.

[@alinameanslight2897]

BOOM!! That was amazing!! I've been trying to learn all of this through various sources, and this video single handedly brought it all together and made it click... Thank you so much!

[@scotchbonnet7]

This was incredibly interesting and helped clear up a couple of areas left vague in my uni course about the structures of the eye. Thanks for the video :D

[@hehebwoy4132]

You really help me in my science class.

[@Bram06]

Hank: ill just sit here while you google it... me: *sight* what am I doing with my life? edit: alright I just googled it and HE REALLY WASNT LYING. DO *NOT* GOOGLE IT

[@kitsunekyubino9345]

Bram06 I COULDN'T STOP LAUGHING!!!! I don't know why. Maybe I'm just desensitized to everything the internet can throw at me?

[@nathandevotta4453]

its better than ASMR

[@digiexploration530]

@@kitsunekyubino9345 that's weird. the pics are horrenouds. you are not supposed to laugh...

[@vulpinedeity3379]

Made me laugh.

[@suhaa6164]

Dunno what I would do without you sir

[@lordspoice5192]

Personally I saw Gold and White in the after effects.

[@blackmesa232323]

It's black and blue!!!!!

[@benchapman4881]

Lord Spoice Not This Again It Has Been Proved To Be Black And Blue So Everyone Shut Up. There Have Been Other Pictures Of It And They Where Black And Blue.

[@lordspoice5192]

Ben Chapman its a joke

[@VCheesey]

Ben Chapman Okay Jayden Smith

[@benchapman4881]

Lol Sorry Just Re Read And Saw How Agrresive It Was. My Apolgies. I Also Thought You Were Talking About The Dress Which Is Getting Old. My Sincere Apolgies

[@thundermontero]

I LOVE listening to this guy. I laugh pretty much very single time.

[@RianKashfi]

I'm unable to see the flag on the white background, obviously because I'm Canadian. lel

[@zhnkbr]

how is "Faiyaz" spelt with so much enunciation but "Rian" so bland (frm bd tooo}

[@gaylecheung3087]

Faiyaz Kashfi Rian it’s to close to your eye, that’s why...

[@abood2010ize]

my teacher spent 3 weeks explaining this and you managed to make me understand in 9 minutes, how are you so good at this?

[@blkpik4993]

Is there something wrong with me, I don't see the ghost effect of the flag. I just see the white screen

[@MrJ3]

You should focus on a point in the middle of the image. It doesn't work if you let your eyes flicker around the screen, it gives your receptors time to adapt and rest.

[@sergiosanchezpadilla1418]

The same happened to me. I do see the ghost but for like .01 seconds. I would say some of us have more resilient cones :P But I don't know, maybe we need more "controlled" conditions :)

[@lobe48]

it helps if you blink quickly while looking at the white screen

[@Emanuel-sl7cd]

It helps if you stand upside down

[@centrifuged0355]

Even I couldn't see any color... 😮

[@stephaniew.5366]

I ❤️ CRASH COURSE!!!!!

[@4_Science]

Wait does light have a varying amplitude? My understanding is that brightness is controlled by the NUMBER of photons, not a variance in the amplitude of those photons.

[@Gigi_Ouija]

The 3D rendition of the eye receiving images was exactly what I needed to be able to conceptualize the different functions of the layers! Thanks :D

[@gabbyavery420]

Wish I knew this information before my AP Bio exam (aka frq1)... Oh well

[@mz00956]

Could you get somehow into the System where the information gets from the eye to the brain and add some signals? Like attach a small cable that can send signals in? If you could decode how your individual eye converts the light into signals, you could then add something to the image that your brain gets. Like Information from a camera for blind people or just a small windows 10 tab where you can see that you are to late for your flight to Europe.

[@federicobau8651]

haaa you killed me when you said : I will just seat here while you google it. hahahaa

[@martagoncalves5605]

Who else is binge watching the entire series?

[@Mattteus]

"You've got sphincters everywhere" it's funny because it's true

[@jediknight533]

It is comforting to know that when our eyes attempt to pop out of our heads that they look like squish/dog toys. The more you know!

[@39ocean]

This is great, but I wished you had talked about lens shape in relation to focusing and vision. That's something I find tricky.

[@Davnyissocoollike]

Using this for my GCSE revision

[@jacoblee6079]

Hank: Tells us to not look up Globe Luxation Me: *Stress levels increasing*

[@Durakken]

Question... If you pop your eyes out randomly should you try to put them back in or call a doctor first? It seems like a bad idea to let your eye just hang there, but trying to get it back in also seems like it might cause damage... So which should you do?

[@ionicwoodsman2855]

When It turned to the blank screen, I just noticed all the floaters in my eyes :(

[@SashKaLakers]

Same here! :((

[@chocolatez9042]

All I saw was a blueish rectangle

[@poolplexer]

same

[@iwuvmuffinz]

You might have aphantasia like me

[@robinchesterfield42]

"Don't Google that." (no pause at all) "I'll wait here while you Google it." Oh, you know us so well...I love all that optical-illusion stuff. A related one is where you stare at a red circle for a long time and then not only do you see this BRILLIANT cyan aura around it, but the aura at one point seems to _squeeze in and shrink the red circle_! Awesome. :)

[@vividvenom7299]

Love how he knows us all so well he knew we were all going to google Globe Luxation.

[@nathandevotta4453]

SCARRED FOR LIFE

[@valeriewalsh4900]

I literally watch crash course for fun. I love these videos more than anythingggggg

[@dm_nimbus]

Fun fact: even talking about globe luxation was almost enough to make me faint. As curious as I may be, I don't think I could make myself google it.

[@alexsitaras6508]

James Craver cover your eyes when you sneeze

[@serenisabella]

Anatomy test on the eye tomorrow! Perfect timing!

[@MsDreamGirl098]

thank you so much for this informative video. I took a few screenshots of the video for my presentation, but I credited you if that's okay. Keep up the good work, you literally saved me in bio :)

[@Melecie]

3:21 for anybody wondering about why you should’t research _Globe Luxation_

[@GamebossUKB]

I fuckin googled it. You want to huh. WELL FKN DONT

[@davidndiulor8428]

Why

[@GamebossUKB]

David Ndiulor you googled it. i can sense you did

[@xitlallimarysolgarcia1822]

+Gameboss UKB OH MY FUCKING GOOD I GOOGLED IT I'M CRYING THE IMAGE HAS BEEN SEARED INTO MY BRAIN

[@xitlallimarysolgarcia1822]

+Xitlalli Marysol Garcia GOD NOT GOOD

[@GamebossUKB]

Xitlalli Marysol Garcia lol internet logic (tells someone not to do it (does it anyway))

[@merlokiii]

Changed the speed to 1/2. Thanks, I like the explanations and the illustrations!

[@101falcon]

Nope I ain't googling it my imagination is cursing me enough as it is with an image

[@abhsk25]

I am a 3rd year medical student but still come to this channel just to get nostalgic about my school years when I was regular here

[@aaronprince8652]

Hank: "Don't Google Globe Luxation" Me: Immediately googles it, Freaks out, Goes back to Video.

[@tefy7632]

omg just in time for my anatomy exam! thank you!!

[@Leroyglasingicbts]

WHY DID I GOOGLE IT

[@sozyarjemil2742]

I love you ,you help me sooo much and although sometimes it's hard to understand and you make me happy and make me to try more to be a doctor

[@rhyannahcielos731]

CrashCourse: Some produce ghost effects... Oh, like how he ghosted me lol

[@colemanliam1]

best timing ever i had biology homework to learn about the eye and then this video came out

[@robmckennie4203]

I didn't see the flag after image. Some kind of indication that you shouldn't move your eyes would have been helpful

[@azn0azn0azn]

Rob Mckennie or you can just do it again

[@InquisitorThomas]

I didn't see anything either and I tried twice

[@robmckennie4203]

Derek Chen Yeah, because my point was that I now can't experience it. Dipshit, the whole point is that when you start watching the video you experience it without having to rewind, it wouldn't have been hard to stick a dot in the middle of the screen and tell people to look there.

[@blast4310]

Rob Mckennie Try blinking while looking at the white screen.

[@robmckennie4203]

George Holland I have very little patience for stupidity.