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 😬
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
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
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
***** 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.
***** 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.
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
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.
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*
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!
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! :)
Vision scientist here. That was a great video, I imagine I'll use that in some of my teaching in future. I really recommend adding a fixation cross to that flag at the start though in order to make it more effective, the illusion can be basically extinguished if people are moving their eyes all over the place.
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.
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
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.
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 . .
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
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!
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.
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.
"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'
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.
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
+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.
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.
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
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.
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
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!
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.
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.
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 :)
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?
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 :)
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. :-)
Very nice crash course! What about the tendency of vision adjusting to staring at the same movement, like scrolling text or playing guitar hero. Is that also the photoreceptors and the optic nerves "getting tired" and keep firering after the movement is actually gone?
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.
so about 2 months ago i was in a store parking lot, looking into the visor mirror and the sun hit my eye at the perfect angle, and I COULD SEE EVERY DETAIL in my iris and it was like looking at a crumbled piece of brown paper...also that's the first time ive seen my eye color.
Yea tht was same for me but after actually staring at one spot for the 30 seconds you'll def see it. I stared on it for a minute and even whole typibg this i'm seeing the dull red lines
