and this video, we're going to begin our lesson on neuro transmitter release, and this process occurs via XO site Asus. And so a well studied example of Exocet Assis is again the release of Nure Oh transmitters in the final step of a neuron signal. And so nure oh, transmitters, as their name implies with the nure oh prefix and the transmit route here are just chemical substances that are released by the end of a neuron in order to transmit a signal or in order to send a signal from one cell to another cell. And a classic example of a neuro transmitter is the molecule called a Seattle coleene and so down below notice that we're showing you this structure of a Seattle cooling and really a settle. Colin gets its name from its structure and so you can see that there is a coleene group right here and in a Seattle group over here and again. That is how a Seattle Colin gets its name. And so one thing to note is that a Seattle cooling is stored in vesicles at the end of a neuron, and it's released by neurons via the process of Exocet Asus in order to trigger a muscle contraction. And we'll be able to see this down below in our example image. And so notice up at the top here. What we have is a neuron or a cell of our nervous system. And so you can see here we have the body of the neuron and hear what we have is the Exxon of the neuron which ends in the bulbs, the ax on bulbs that we have here in the end. And so notice that this this image that we have down below is really just zooming into the bulb of the accent. And so you can see that this here represents the end of the Exxon of the neuron. And so, as we mentioned up above, a Seattle cooling is packed into vesicles at the end of the neurons Exxon. And so notice that we have these vesicles that air right here. And these vesicles again are packed with the acetyl Colin molecule that we described up above. And acetylcholine is going to be the neuro transmitter in this case. And so notice over here on the right hand side of our image, what we have is a muscle cell in this red line represents the muscle cells, plasma membrane and embedded in the muscle cells. Plasma membrane. We have these acetyl Colin receptors, and so what needs to happen is when an action potential makes its way down the Exxon of the neuron. Ultimately, that action potential is going to trigger calcium to be released into the cell. And calcium we know acts as an interest cellular signal. And this calcium ultimately is going to be responsible for these vesicles to fuse with the Exxon's plasma membrane via the process of Exocet Asus in order to release those acetyl Colin neuro transmitters. And so that's exactly what we're seeing over here on the right hand side. So notice calcium comes into the cell and triggers the X aside toe sis of these vesicles. And so here. What we can do is write in Exocet Assis, and so you can see that all of these acetylcholine neuro transmitters air being released into the space. And there's acetyl Coleene molecules are capable of binding to the acetylcholine receptors, and when they do that, they can trigger a muscle contraction within the muscle cell. And so what, you can see here is that Exocet Asus plays a big role in the, uh triggering of a muscle contraction. And so this year concludes our introduction to Nure Oh transmitters. And as we move forward in our lesson, we're going to talk more details about exactly how nure oh transmitter release occurs. And so I'll see you guys in our next video.

in this video, we're going to introduce snare fusion proteins. And so you might recall from some of our previous lesson videos where we first introduced endo psychosis and exocet. Oh, sis. We briefly mention that these integral membrane proteins called fusion proteins are important for allowing membranes to fuse together during the process of endo psychosis and exocet. Oh, sis! And so here we are talking about very specific fusion proteins called snares. Now, it's also very important to note that vesicles and plasma membranes will actually naturally repel each other. And so the reason for this natural repulsion is because vesicles and plasma membranes are both made of phosphor lipids and those phosphor lipids have negatively charged phosphate groups. And so the negatively charged phosphate groups in the vesicles will repel the negatively charged phosphate groups in the plasma membranes. And so that is why there is this natural repulsion between the two. And so in order for endo psychosis or exocet, oh, sis such as neuro transmitter exocet doses to occur. Uh it is going to need to overcome this natural repulsion between the vesicles and the plasma membranes. And in order to overcome that natural repulsion, it is going to require many different types of proteins. Now moving forward. We're not going to talk about all of the different types of proteins that are involved with. Overcoming the repulsion however, we are going to focus in on the integral membrane fusion proteins called snares. And so really there are two main types of snares that you should be familiar with. And we have them numbered here number one and number two. And so the first snare that you should be familiar with is called the V snare. Now, as its name implies with the v. The v snares are going to be found on the intracellular vestibule cytoplasmic surface. And so you can see that the V. And vesicles is for the V. And V snare. And so by intracellular vesicles, cytoplasmic surface. We are really saying that the V snares are found on the outside of the intracellular vesicles. Now it's also important to note that sometimes V snares are referred to as our snares. And the reason for that is because Argentine, who's one letter code is r is a critical amino acid residue in the snare protein. And so it's important to know that V snares and our snares are the same type of snare. And so one way that helps me remember that V snares and our snares are the same type of snare. Is that when I think of the snare and our snare I think of VR or virtual reality. And so notice down below we're showing you this kid with these virtual reality reality goggles. And so you can see that the virtual reality can remind you of the V snare and the arson air and that the V snare and arson there are the same thing, they're referring to the same thing. Now the second type of snare is called the T snare and the t snare is not going to be found on the intracellular vesicles, cytoplasmic surface. Instead the T snare as its name implies, is going to be found on the target membrane cytoplasmic surface. And so you can think the T. And target membrane is for the T. And T. Snare. Now T snares are also sometimes referred to as Q. Snares. And the reason for that is because a glutamine residue is critical for the function of the protein and Q. Is the one letter code for glue to me. And so one way that helps me remember that T. C. Snares and Q. Snares are the same type of snare is I remember this cartoon character here looking at himself in the mirror and saying hey there, cutie looking good. And so that will help you remember, Hopefully that Q. Snares and T snares are the same type of snare. And so here in the middle, what we have is a representation of the end of an axon. To help you better understand the difference between the T. Snare and the Q. The snare and the V. Snare. And so notice here we have the axon of the neuron here and at the end, what we have here is a vessel and the vessel is going to perform exocet, oh sis to exit the end of this neuron. And so packed inside the vesicles is going to be some kind of neurotransmitter, perhaps acetylcholine. And so notice here in green these green structures that are on the outside of the vesicles uh we call these the vis the V snares. And the V snares are also known as our snares. And so we could have put either V or are into this blank. And then over here on this side on the target membrane uh central on the target membrane, cytoplasmic surface. What we have is the T. Snare. And again, the T snare is also known as the Q. Snare. So we could have put T or Q into either of those blanks. And so as we move forward in our course, we're going to talk about the specific steps that are required in the process of Exocet Oh, sis where the V snare will come into contact with the T snare in order to allow the vestibule to fuse with the target membrane and release the contents of the vestibule, release the neurotransmitter. And so again, we'll be able to talk about that step by step process as we move forward in our other videos. But for now this year concludes our brief lesson on snare fusion proteins. And I'll see you all in our next video

All right. So now that we've introduced the snare fusion proteins the V snare and the T snare and this video, we're going to talk about the process of Nure Oh, transmitter, Exocet, Asus and so nure Oh, transmitter release via Exocet Asus occurs in a four step process that we have number down below in our text. And of course, the numbers that we have in our text here correspond with numbers that we have down below in our image. Now, over here on the far left, what we have is a little reminder of the snare fusion proteins from our last lesson video. And so we know that here, what we have is the V snare on the vesicles membrane. And so this green structure here represents the V snare, and we know that the V snare and some of your textbooks is also referred to as the R snare. And we remember that because the are is like virtual reality. And then, of course, over here and the target membrane, what we have is the T snare, and the T snare is this blue structure that you see here in the target membrane and again, and some of your textbooks. The T snare is referred to as the Q snare, and we remember that because we think about a cutie. And so now that we refresh our memories on these snare fusion proteins, we can talk about the first step of this four step process to neuro transmitter Exocet toasts. And the very first step is snare binding. And, of course, during snare binding, the V and the T snare are going to bind to each other and induce confirmation. Allchin changes and these confirmation all changes are going to draw the two membranes closer together. It's going to draw the vesicles membrane closer to the target membrane, even though they have this natural tendency to repel each other again. It's the snare proteins, fusion proteins that play a big role in allowing these two membranes to be drawn together and so down below. And our step number one, which again corresponds with step number one up above you can see that we have V and T snare binding and so noticed that over here we have our vesicles, and over here we have our target membrane and noticed that the V Snare and T snare are now bound to each other here, and they are inducing confirmation. All changes in each other that again are drawing the two membranes together. The vestibule membrane and the target membrane are being drawn closer together. So now moving on to the second step, What we have is Hemi fusion, and this is when changes in the curvature and the latter lateral tension and both the vesicles membrane and the target membrane are going to induce Onley the outer sheets of the membranes to fuse with each other. And so it's not the inner sheets it's on Lee, the outer sheets that air fusing. And so it's on. Li, like part of the membranes, are fusion, partial fusion. And that's exactly what Hemi Fusion is referring to because the prefix Hemi means partial and so Hemi fusion means partial fusion. And again, that's why it's on Lee inducing the outer sheets of the member interviews, not the inner sheets just yet. And so if we take a look at our step number two down below, which again corresponds with step two up above, we have Hemi fusion again, partial fusion, and so you can see that the vesicles Liz, right here. And the target membrane is right here and notice that it's the outer sheets that are fusing. So you can see here the outer sheets are fusing and the inner sheets are still not fusing yet. And so you can see that we have this gap here where the membranes are beginning to fuse. And so really, that is it for step number two and and step number three. What we have is the creation of a fusion poor and so continued changes and curvature and lateral tension. And again, both the vesicles membrane and the target membrane are ultimately going to fuse both of the membrane sheets, the outer and the inner membrane sheets so that the vesicles is completely fused to the target membrane. And this is going to create a small opening or a small poor in the, uh, membranes. And so this is referred to as the fusion poor. And so, if we take a look at our step number three down below, which of course, correspondence will step three of above, we have the generation of the fusion poor and so notice that now both membranes have been merged. Both sheets of the membranes have been merged. And so it creates this little tiny fusion poor here where neural transmitters can begin to make their way out to, uh, the extra cellular space. And so, in step number four, what we have is release narrow transmitter release to be more specific. And so this is when the fusion poor is going to expand. And, of course, release Nure oh transmitters, uh, into the extra cellular space. And then the fused membrane is going to take a more relaxed position. And so if we take a look at stop number four, notice that we have release of the neurotransmitters and so notice that the membranes are now completely fused and it's starting to take more of a relaxed state, the fusion poor has expanded. So now all of the neuro transmitters can be released into the outside of the cell. And so really, this is the four step process for Nure Oh transmitter Exocet Asus, and we'll be able to get some practice applying some of these concepts as we move forward in our course. So I'll see you guys in our next video