When the action potential reaches the axon terminals, something needs to happen in order to transfer that signal from one neuron to another.
Watch as Leslie explains the role of neurotransmitters and how their release results in a signal in other cells, organs, or glands.
Enjoy!
Transcript of Todays Episode
Hello and welcome to another episode of Interactive Biology TV, where we’re making biology fun! My name is Leslie Samuel. In this episode, Episode 16, I’m going to be talking about the neurotransmitter. We’ve been talking about the nervous system, we’ve been talking about neurons, and we’ve been talking about the action potential and how that travels along the neurons all the way to the ends of the neurons. What we’re going to do today is we’re going to focus a little more closely at the end of the neurons, the place that we call the axon terminal.
Now, neurons do not exist in isolation. They are interconnected, they connect to other neurons, as you can see right here. There’s a connection here, you can see there’s another connection here. Basically, when there’s a signal in one neuron, that can send a signal to many other neurons or glands or organs. This is the way the nervous system communicates, and there needs to be these connections, and signals need to go from one neuron to the next.
What I’m going to do is I’m going to zoom in on this connection here and we’re going to take a closer look at it. So we’re looking at that connection, and there are a few terms that you need to understand. The connection between the neurons, we call that the synapse. The synapse is the connection between one neuron and another neuron, or between one neuron and another cell, organ, or gland. We are basically talking about the place where neurons connect with other cells.
Another term that you need to know is the synaptic cleft, and the synaptic cleft is basically this space here that’s between the neurons. Most neurons don’t connect physically. There’s a small space between those neurons where they connect and there are some important things that are happening there, and we’re going to look at those things today.
Another term that you need to know would be the synaptic vesicles, and you can see there are a number of vesicles in here. What’s unique about these vesicles is that inside of those vesicles, we have neurotransmitters. You can see examples of neurotransmitters here. This is a neurotransmitter, and we have 3 in here, 2 in here, 1 in here. These are all neurotransmitters.
Another term that we need to be familiar with would be the receptor. The receptor is the protein or the part on the receiving cell that binds to the neurotransmitter. You can see a perfect example of one here.
Some other terminology that’s not on this image is, since we’re calling this the synapse, we have 2 membranes. We have this membrane here, and we have this membrane here. The membrane that comes right before the space, we call the pre-synaptic membrane. So that’s this membrane here. And the membrane that comes after the space, and that would be this membrane here, you guessed it! We call that the post-synaptic membrane. So those are the terms that I want you to be aware of as we go into talking about what happens when the action potential reaches the axon terminal.
We’ve spoken about the action potential, and the action potential travels along the axon. I want you to imagine with me an action potential coming down this axon and reaching the axon terminal. Now, there are a number of things that happen when the action potential reaches the axon terminal. One of the most important things that’s happening is we have voltage-gated calcium channels that open. When voltage-gated calcium channels open, calcium ions that are concentrated outside (I’m going to write Ca++) are going to rush into the cell.
This is a very important event because it causes something that’s very significant. It causes these synaptic vesicles to fuse with the pre-synaptic membrane, and you can see an example of that happening right here. When the synaptic vesicle fuses with the pre-synaptic membrane, that causes the neurotransmitter to be released into the synaptic cleft. You can see an example of a neurotransmitter that’s released right here, and of course, there’s another one right here.
Now, what then happens is also very important. The neurotransmitter binds to the receptor. When the neurotransmitter binds to the receptor, that can cause a signal in the receiving cell. So we can have a signal in this cell because neurotransmitters are being released and that binds to the receptors, and that causes a signal in the receiving cell.
This is how we can go from one neuron to the next neuron. Signals are travelling rapidly and they need to be routed to the right place. The way the neurons are going to communicate with each other is by this process of releasing neurotransmitters. That’s all the content for this video. If you have any questions about it or any comments, go ahead and leave a comment beneath this video in the comment field. I’d be happy to answer your question, or even make a follow-up video to answer your specific question. That’s all for this video, and I’ll see you in the next one.
About The Author Leslie Samuel
Leslie Samuel is the creator of Interactive Biology. He created this site to help Make Biology Fun and has the goal of making this the biggest and best biology resource on the net.
We have videos on most of that. Check the site listed in the description. Go to the videos page!
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@neemasch We have videos on most of that. Check the site listed in the description. Go to the videos page!
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We have videos on most of that. Check the site listed in the description. Go to the videos page!
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This is really helping me understand everything soooooooo much better! Thank you so much!
I’m gonna keep watching for fun too!
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This is really helping me understand everything soooooooo much better! Thank you so much!
I’m gonna keep watching for fun too!
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Leslie,
This video is very helpful, but I have three questions:
1. What is it about the Ca+ entering the axon terminal that signals the synaptic vesicles to fuse with the presynaptic cleft and release neurotransmitters? How do the Ca+ ions interact with the vesicles to make them do that?
2. How do the neurotransmitters know to bind to the receptors on the postsynpatic cleft and not just float away in the extracellular fluid? Is there a charge drawing them toward the receptors?
3. You said that once the neurotransmitters bind to the postsynaptic receptors, that causes a signal inside of the cell. If this cell is not the final destination of the action potential, does the signal initiate another action potential within the cell to send down its axon? Or, in general, I guess I just want to know an example of what kind of signal the neurotransmitters would be sending.
I know these questions are a bit involved. I’d appreciate your explanations though! Thanks
Melissa
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Lrsamuel Reply:
January 24th, 2012 at 10:04 pm
WOW, that’s A LOT to answer in a comment. Not sure I’ll be able to answer them fully, but here are my quick responses:
1. Calcium interacts with proteins in the membrane of the vesicles and on the presynaptic membrane (SNAP-25, Syntaxin, Synaptotagmin, Synaptophysin – if I’m remembering correctly), causing them to interact in a way that helps the membranes fuse. In terms of the underlying exact mechanism, I don’t know more than that.
2. The space is VERY SMALL. There isn’t an attraction, but the transmitters fit into the receptors in a way that causes the changes necessary. Some of the transmitter may leak out, but the transmitters don’t stay around long. They are broken down by enzymes.
3. Yes, it can cause another action potential in the postsynaptic cell, which is then the presynaptic cell for the next postsynaptic cell.
Hope that helps!
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Melissa Fling Reply:
January 25th, 2012 at 12:10 am
Perfect,
Thank you!
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Ok so I am a premedical student in college and these videos are soo useful for physiology class! thanks for your work.
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Jeanna Dalton Reply:
February 15th, 2012 at 6:26 pm
We are studying the nervous system right now in physiology, and I agree with you that they are proving very useful! My professor is a med. doctor and sometimes she speaks as if we are a group of professors too! I love these videos because they are helping me to understand what she is trying to help us learn!!!!
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Leslie Samuel Reply:
February 16th, 2012 at 9:03 am
Great to hear Jeanna, glad you are getting value from the videos. Stay tuned for more!
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Ok so I am a premedical student in college and these videos are soo useful for physiology class! thanks for your work.
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I liked it when students were INTERACTING in the lectures…
now is alot more boring than before 
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I liked it when students were INTERACTING in the lectures…
now is alot more boring than before 
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Leslie, thank you so much from the bottom of my heart! Ur amazing!
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Leslie, thank you so much from the bottom of my heart! Ur amazing!
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keep posting nervous system videos please, i love your videos so much XD
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keep posting nervous system videos please, i love your videos so much XD
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Release of neurotransmitters usually follows arrival of an action potential at the synapse, but may also follow graded electrical potentials.
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Release of neurotransmitters usually follows arrival of an action potential at the synapse, but may also follow graded electrical potentials.
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May I ask what will happen to the neurotransmitters after they have stimulated the channels on the dendrite of the next neuron? Will they go back to the vesicles? If no, how can they deal with the coming next signals????
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Leslie Samuel Reply:
May 1st, 2012 at 3:41 pm
They are usually broken down by enzymes and then taken back into the presynaptic terminal and reassembled for reuse.
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I loved it thank you do much
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I loved it thank you do much
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Thank you very much Leslie, you’re a BOSS.
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Thank you very much Leslie, you’re a BOSS.
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omygod. this video saved my life
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omygod. this video saved my life
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what controls the amount of neurotransmitter released?
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action potential is an all or none concept. for more neurotransmitter to be released you need more action potentials. hope that helps!
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You ROCK you are a great teacher and thank you for what you do
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You made physio that much more fun and easier to learn. I just may pass my class!
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Great video! I do have a question: what is the role of magnesium in this process?
Thanks in advance!
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Thank you so much
I wonder how people figured all this out in the first place!!
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Great vids!thanks so much!
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THANK YOU SO MUCH
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Leslie Samuel… we meet again..
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This is a very good video. You explained the process very well. Our Anatomy book made the release of neurotransmitters very unclear because it did not distinguish between the postsynaptic/presynaptic membranes. Thanks for the informative video!
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I love your pronunciations and your style of explaining things. For someone who speaks English as a second language , is important to understand clearly (as you wonderful do ) terms and names. I am looking for a lesson with how neurotransmitters are retrieved.
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Thank you so much for your videos. They are very helpful! I have a question with regard to the action potential. Is it correct that the action potential is caused by the neurotransmitters bringing EPSP and IPSP where the summation is sufficient to depolarize the membrane to its threshold of exicitation? Is the Action potential also generated by the neurotransmitters binding to ionotropic receptors which cause sodium to rush in? And at last, can you tell me what is the case for Serotonin? Thanks!
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VERY HELPFUL!!!
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Very helpful! can you go into more detail about how protein kinase in here.
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Thank so much, it’s so much easier to understand with a narration and diagram, thank you!
I was just wondering how are the Neurotransmitter made? Serotonin is produced for example by exercise, how is it that the serotonin neurotransmitter is produce in neurons?
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like a boss thanks
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thank you very much. Mr Samuel
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GOOD DAY, CAN YOU GIVE ME THREE WAYS IN WHICH A NEURONE IS SIMILAR TO OTHER ANIMAL CELLS
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Thank You soooo much, I got an “A” on my last A&P exam!;~) You explain things very well. Do you have any …more(?)… interactive lessons? For example clicking on a word in the image to see it defined or labeling exercises?
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Thanks a lot, I’m currently doing my psychology A level and your video was a lot of help. I also wanted to ask how do the synaptic vesicles fuse with the presynaptic membrane. I haven’t watched your previous videos so I don’t quite understand what exactly the synaptic vesicles are and what is the pre-synaptic membrane made of etc.
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Thank you so much! This video and the previous videos have helped me a lot!
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