Let's take a look, this is the eye. The eye ball, if we look of course, these structures we know this is a lens cornea. [FOREIGN] The most important thing actually here is the yellow tissue here. [FOREIGN] tissue. [FOREIGN] The neuron responsible for the detectance of a photon. [FOREIGN] Actually other neuron types other than. This neuron is a output neuron and this sends its axon to the brain. Well [FOREIGN] let take a look here. [FOREIGN] Make it a section. [FOREIGN] You can see this deep in the layers [FOREIGN] is a structure. [FOREIGN] Okay, this side is this side okay? Is close to this black one, you see this is a black tissue here. [FOREIGN] This photoreceptor and then here. [FOREIGN] This one, this is a, In the nuclear layer [FOREIGN] mainly bipolar cell. [FOREIGN] Horizontal cell and endocrine cell. [FOREIGN] Output a neuron, send to the brain to have it's axon go to the brain. Okay, this is the another cartoon to show this neurons, this is actually the photoreceptor, okay? There are two types of photoreceptors you can see, one is actually very long and very thin. This one is called a rod photoreceptor [FOREIGN] now this one is a different one, okay? [FOREIGN] photoreceptor [FOREIGN] okay? These two type of cells should be responsible for transduce the light into the electric signal, okay? Detector and then you have bipolar cell, this vertical pathway. [FOREIGN] Your bipolar cell to ganglion cell. [FOREIGN] In this outer flexible layer. [FOREIGN] You get kind of horizontal cell. [FOREIGN] very special, they don't have the axle send the information to downstream neuron. And what they do is actually make the [FOREIGN] formation modulation [FOREIGN] okay? [FOREIGN] Okay, so let's take a look actually how this guy, this photoreceptor detects the light. [FOREIGN] This is a cartoon of the photoreceptor. Of course you know its easy to [INAUDIBLE] photoreceptor, right? [FOREIGN] This is a cone for the receptor, and the light detection region only happened at this region. [FOREIGN] Outer segment [FOREIGN] this we call [FOREIGN]. We call segment here [FOREIGN] this is outer segment. [FOREIGN] Terminal [FOREIGN] [FOREIGN] Okay. Why you need to make such a system with too many discs there? [FOREIGN] With the tender, harder surface area [FOREIGN] detector, right? [FOREIGN] Design using a principle [FOREIGN] in the olfactory system [FOREIGN] [FOREIGN] Region here, there is a pocket [FOREIGN] is this chemical able to absorb the photon, okay? This is important, it's not the protein, this is an 11 Cs. 11 Cs is actually between the [FOREIGN] okay, cyst. [FOREIGN] If we have a photon, here this molecule, this chemical where as absorbed with the photon energy. The energy will be used to break the bond [FOREIGN] what will happen to the protein? [FOREIGN] The whole [INAUDIBLE] protein act, this confirmation [INAUDIBLE]. Now protein, [FOREIGN] activate the protein, time to bind it to the protein [FOREIGN] okay. [FOREIGN] Professor [FOREIGN] okay, the photoisomerization, [FOREIGN] okay? [FOREIGN] Okay? Yeah, the same thing, [FOREIGN] okay? This actually, the lighting effect, so let's further take a look at this structure. This is the ROD photoreceptor out the second one, in the second one, right? So, [FOREIGN] increases the surface area to, [FOREIGN] this direction or this direction or that direction. [FOREIGN] Now let's take a look actually about the disk membrane [FOREIGN] this is the real disk inside. This is actually the [FOREIGN] It's not connected to the disc [FOREIGN] electric activity of the neuron, coming from where? [FOREIGN] Here is coming from a very important concept [FOREIGN] so, you have a photon. [FOREIGN] How do you have electric signal on this [FOREIGN] so you need something to connect theses two processes. So why is happening here, why is happening here? That means that you have to have a second messenger [FOREIGN]
