016 The release of Neurotransmitter
When the action potential reaches the axon terminals, something needs to happen in order to transfer that signal from one neuron to another.
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.