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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.
1. February 2011 at 1:04 pm
@Skoty6 That’s a great question. Yes, exocytosis is the process that is used to release the neurotransmitter from the axon terminal. This isn’t the only example of exocytosis, but it definitely is one.
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Amélie Reply:
January 14th, 2012 at 6:39 am
I’ve learned that during the proces of this specific exocytosis, a snare complex is formed. Could you please explain to me what a “snare complex” exactly is?
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4. February 2011 at 7:23 pm
What happens to the vesicle once it releases the neurotransmitter?
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4. February 2011 at 7:28 pm
Does the synaptic vesicle necessarily release ALL of its contents?
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5. February 2011 at 8:31 pm
@jmlevins1 In order to release the neurotransmitter, the vesicle actually fuses with membrane. Once it fuses with the membrane, that causes the content to be released, which in this case would be neurotransmitter.
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5. February 2011 at 8:32 pm
Yes, once the synaptic vesicle fuses with the membrane, it releases all its contents. However, all of the synaptic vesicles don’t necessarily fuse with the membrane to release Neurotransmitter. Some of them remain in the synaptic terminal. Hope that helps
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5. February 2011 at 8:32 pm
@jmlevins1 Yes, once the synaptic vesicle fuses with the membrane, it releases all its contents. However, all of the synaptic vesicles don’t necessarily fuse with the membrane to release Neurotransmitter. Some of them remain in the synaptic terminal. Hope that helps
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28. February 2011 at 8:24 pm
I can’t believe how much your videos have helped! I could not make sense of any of this until I watched a few of your episodes! Thank you so much for taking the time to post these videos! I look forward to watching more!
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28. February 2011 at 8:49 pm
That’s so awesome to hear. There are definitely many more coming, so stay tuned
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28. February 2011 at 8:49 pm
@kpollock313 That’s so awesome to hear. There are definitely many more coming, so stay tuned
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4. March 2011 at 1:33 pm
How many Action Potentials are needed in order for a neurotransmitter like glutamate to be released?
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Leslie Reply:
March 4th, 2011 at 3:14 pm
Hi Stephanie,
It only takes 1 Action Potential in order for a neurotransmitter to be released, and that’s the same with Glutamate.
All the best!
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7. March 2011 at 1:02 am
definitely agree, these are helping. Thanks!
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7. March 2011 at 5:36 am
@stephpina2 You’re welcome!
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10. March 2011 at 2:32 am
thank you!
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10. March 2011 at 6:58 am
You are welcome
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10. March 2011 at 6:58 am
@polygontaco You are welcome
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12. March 2011 at 6:46 pm
@megaloveistheanswer That’s so awesome. Glad the videos have helped you. Now go and get that A+ and make sure to come back and tell me about it
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19. March 2011 at 5:01 pm
This video is very informational and explains all the details needed for any test related to the process of how the neuron works. Thanx
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12. April 2011 at 9:26 am
Hello, I liked your video, it explains things simply and clearly.I have a question though:
When a signal traveling on the axon reaches the synapse a neurotransmitter is released.This can be let’s say dopamine or GABA or smth else, and is either inhibitory or excitatory, correct?Then the receiving neuron binds this neurotransmitter with its receptors and sends an electrical signal to the core of the cell, am I correct?The question is what kind of signal is this one – excitatory or inhibitory?10x
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12. April 2011 at 6:17 pm
It depends on the ion channel it opens. If it opens a Na+ channels, that causes an excitatory signal. If it opens a Cl- channel, that causes an inhibitory signal. GABA is usually an inhibitory Neurotransmitter. Dopamine can be either excitatory or inhibitory. However, they have different receptors that can open different channels that allow different ions to flow in. This can result in an excitatory or inhibitory signal. Hope that helps.
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12. April 2011 at 6:17 pm
@diimtarsh1 It depends on the ion channel it opens. If it opens a Na+ channels, that causes an excitatory signal. If it opens a Cl- channel, that causes an inhibitory signal. GABA is usually an inhibitory Neurotransmitter. Dopamine can be either excitatory or inhibitory. However, they have different receptors that can open different channels that allow different ions to flow in. This can result in an excitatory or inhibitory signal. Hope that helps.
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13. April 2011 at 2:55 am
Hello, thank you for your answer, that really helped me. Have a nice day
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13. April 2011 at 2:55 am
@InteractiveBiology Hello, thank you for your answer, that really helped me. Have a nice day
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13. April 2011 at 6:20 am
@diimtarsh1 You are very much welcome!
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17. April 2011 at 8:33 am
very nice video!! But could please distinguish between an electrical synapse and a chemical synapse and the way the impulse travels along them??
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Leslie Reply:
April 17th, 2011 at 9:22 am
Sure Varsha,
Electrical Synapse: Gap junctions connect the cells so that they are essentially “electrically connected”. When there is a signal in one cell, the ions flow to the next cell causing a signal in that cell.
Chemical synapse: This is the one described in the video, and relies on Neurotransmitters that are released into the synapse. The neurotransmitter binds to receptors and a signal is generated in the next neuron.
Hope that helps!
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varsha Reply:
April 17th, 2011 at 11:15 am
so does that mean that there isnt any need of a neurotransmitter in the case of an electrical synapse??
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Leslie Reply:
April 17th, 2011 at 11:27 am
That’s correct.
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17. April 2011 at 12:00 pm
thanks for that.
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Leslie Reply:
April 17th, 2011 at 1:36 pm
You’re very much welcome!
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18. April 2011 at 3:31 am
great video helped me alot but i have another problem that is related to the classification of neurotransmitters and the drugs effecting them like Ach effected by botulium toxin or GABA by allyglycine etc that is very complicated can you tell me an easy way to understand it…plz
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19. April 2011 at 9:46 am
Glad the video helped. Unfortunately, I don’t have a good summary of that at the moment. Will probably get to doing something like that the next time I cover the Nervous System, but that won’t be for a while. Hope you are able to find good resources. Do a google search and see what you come up with (if you haven’t already).
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19. April 2011 at 9:46 am
@hadooish Glad the video helped. Unfortunately, I don’t have a good summary of that at the moment. Will probably get to doing something like that the next time I cover the Nervous System, but that won’t be for a while. Hope you are able to find good resources. Do a google search and see what you come up with (if you haven’t already).
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23. May 2011 at 8:58 am
this video is very grate
but i have question : what the job of mitochondria the found in presynaptic membrane?
thank you very much
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Lrsamuel Reply:
May 23rd, 2011 at 3:46 pm
Cells need energy for all of their functions to happen. There are a number of things happening in the presynaptic cell that requires energy. The Na/K pump is one example. It’s found everywhere and requires ATP. Also, in order for the Neurotransmitters to be taken back into the presynaptic cell, that also requires ATP. ATP is made in mitochondria.
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23. May 2011 at 6:24 pm
What about the Na+ ions that rush in when ACh attaches to receptors?
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4. September 2011 at 3:41 pm
the action potential is caused by an electrical signal..but now the next neuron recieves a neurotransmitter..which is a chemical..then how does the signal go furthur??
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5. September 2011 at 6:36 am
Check out episode 015. That answers your question.
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5. September 2011 at 6:36 am
@juhidgenius Check out episode 015. That answers your question.
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9. September 2011 at 9:15 am
thanks a lot
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18. October 2011 at 1:35 pm
Hello I would like to See some videos about EPSP & IPSP and also about the Summation which classified into temporary and simultaneously
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18. October 2011 at 9:15 pm
We have videos on most of that. Check the site listed in the description. Go to the videos page!
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18. October 2011 at 9:15 pm
@neemasch We have videos on most of that. Check the site listed in the description. Go to the videos page!
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25. October 2011 at 1:41 am
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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24. January 2012 at 6:41 pm
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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5. February 2012 at 1:38 pm
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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7. February 2012 at 11:12 pm
I liked it when students were INTERACTING in the lectures…
now is alot more boring than before 
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27. February 2012 at 3:45 pm
Leslie, thank you so much from the bottom of my heart! Ur amazing!
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3. March 2012 at 5:33 pm
keep posting nervous system videos please, i love your videos so much XD
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14. April 2012 at 12:04 am
Release of neurotransmitters usually follows arrival of an action potential at the synapse, but may also follow graded electrical potentials.
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1. May 2012 at 9:57 am
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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4. May 2012 at 3:25 pm
I loved it thank you do much
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