Vision: Crash Course Anatomy & Physiology #18

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Next stop in our tour of your sensory systems? VISION. With a little help from an optical illusion, we take a look inside your eyes to try to figure out how your sense of vision works — and how it can be tricked.

Pssst… we made flashcards to help you review the content in this episode! Find them on the free Crash Course App!
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Chapters:
Introduction: Optical Illusions 00:00
How Does Light Work? 1:31
Structure of the Eye 2:31
Layers of the Eye: Fibrous, Vascular, and Inner Layers 3:33
The Retina 4:56
Rods and Cones 6:07
How do Optical Illusions Work? 7:15
Review 8:33
Credits 9:14

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43 Comments

  1. the content is so well structured, but it's a shame that every single pause is edited out. I find it quite stressful to watch because there is not a tenth of a second between sentences. In addition why is he speaking so fast?

  2. God is so complex!!!!! by the way you are the king of the nerds! memorizing whole books, Jesus Christ!!!! you never stop talking not even to take a breath.

  3. also, just an FYI the photoreceptors don't directly connect to the bipolar cells, same with how the ganglion cells connect to the bipolar cells. There's another layer of amacrine cells and horizontal cells that allows the information from the photoreceptors to converge onto the ganglion cells. It should look like this, ganglion cells –> amacrine cells –> bipolar cells –> horizontal cells –> photoreceptors

  4. maybe someone else can confirm, but I don't think the explanation for afterimages is correct. In order to explain the phenomenon of afterimages you'd need to introduce the idea of colour opponency. From what i've learned, prolonged exposure to a certain colour (like red), will cause bleaching of the photo pigment. Then looking at a neutral surface (like white) will cause a rebound effect, where the ganglion cell fires below base rate causing you to perceive the opposite colour (hence, green)

  5. I sort of saw a phantom image of the flag although I looked away from it. So weird of our eyes can be easily fooled. I enjoy these videos so much.

  6. I always thought invisible light leaves the eye, bounces off the object, returns and the brain tells you what you're seeing. I can't find that no where on the web. Darn it

  7. 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*

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