022 Re: Akbar – Inactivation of V-gated Sodium Channels

This is a video answering Akbar’s question regarding the difference between the inactive and closed states of voltage-gated sodium channels.

Watch as Leslie explains this difference using a box.

Enjoy!

Transcript of Today’s Episode

Welcome to another episode of Interactive Biology TV, where we’re making biology fun! My name is Leslie Samuel. In today’s episode, I’m going to be answering a question that was left on my blog. On Episode 12 where I spoke about the absolute and relative refractory periods, a question was left by Akbar, and his question was, “Can you please elaborate a bit more on the inactive state of the sodium channel? How does it differ from the closed state?” That’s a very good question and I’m glad he asked it.

In order to illustrate the difference, I’m going to use this box here. The type of box doesn’t matter too much. Let’s say that this box is a voltage-gated sodium channel. There are 3 states that this box can be in. It can be closed, which you can see right now, and it can be open, and it can be inactivated. The way this works is we have 2 gates. These are the 2 gates. I’m going to call this the activation gate, and I’m going to call this the inactivation gate.

So we have a stimulus that comes along, and the stimulus causes the membrane potential to become more positive, and it reaches the threshold. Now, the cool thing about this activation gate is that it’s positively charged. Imagine that you have a bunch of positive charges inside here, and let’s say it’s inside the cell, what is that going to do to the positive charge of the gate? Now, you probably know that like charges repel, and opposite charges attract. Well, we have like charges here, and as that charge builds up, that positive charge is going to cause the positively charged activation gates to open.

When that happens, within 0.5-1.0 millisecond, the inactivation gate automatically closes. That has to do with the structure of the gate, the structure of the channel, and a few different properties that I’m not going to go into. But basically, the idea is once it opens, this just closes automatically after a certain period of time. That period of time would be 0.5-1.0 millisecond. Once it’s inactive, you can’t re-stimulate it. The only way for you to re-stimulate the channel is that it needs to be reset to the closed state. As we said, the activation gate is positively charged, so when the second phase of the action potential happens and potassium rushes out of the cell, the cell becomes more negative, and as it becomes more negative, this gate now gets pulled in so that the channel closes.

So the difference between inactive and closed is: inactive means that the inactivation gate is closed; when it’s fully closed, it’s when both gates are closed, so the activation gate now is closed, and it’s ready to start another action potential.

I hope that clarifies it for you, Akbar, or anyone else that’s listening. If you have any more questions about any of the topics, please feel free to leave them in the comments below, and like I said, like you’re seeing here, I’d be more than happy to make a follow-up video or answer your question in the comments. That’s it for this episode, and I’ll see you in the next one.



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  • Thank you, this was very helpful. All of your videos have been helpful in studying for an upcoming exam.

  • Hi Susan,

    I’m really glad you are finding value in the videos I’m producing, and I’m also glad it was helpful in studying for your upcoming exam. Make sure to stay tuned to the site because I’m trying to post Biology Videos on a regular basis to expand the video library. Thanks for leaving your comment 🙂

  • your videos are awesome.. your explanation explains more than what it is inside the book.. These videos are very good.

  • Hi Alanie,

    First off – thank you for your comments.

    To answer your question, the typical resting potential of a neuron ranges between -50 and -80 mV, mostly around -70 mV. Hope that helps. All the best!

  • Thanks man, this video helped us a lot. Definitely subscribing to your channel. =]

  • Hi Leslie I have created a youtube account specificlly so that I can post this comment. I have got a biology exam next week and your videos have been the xornerstone of my revision I need to meet an offer from the University of Cambridge in the UK and your videos have helped me more than anything. Most importantly, they are consistently really interesting and you can definitely be credited with enthusing hundreds about biology. You can see by the amount of views your videos get that you have be

  • en an inspiration to many, most of whom will not have a youtubd accont to express their gratitude. You enable thousand of people who do not have access to high quality education to have access to well thought out presentations of fascinating topics, or rather topics hat become fadcinsting when you present them! You are a great ambassador for biology, keep on educating and inspiring future generations. Another fantastic video! We all appreciate what you are doing Leslie.

  • Hi Leslie I have created a youtube account specificlly so that I can post this comment. I have got a biology exam next week and your videos have been the xornerstone of my revision I need to meet an offer from the University of Cambridge in the UK and your videos have helped me more than anything. Most importantly, they are consistently really interesting and you can definitely be credited with enthusing hundreds about biology. You can see by the amount of views your videos get that you have be

  • en an inspiration to many, most of whom will not have a youtubd accont to express their gratitude. You enable thousand of people who do not have access to high quality education to have access to well thought out presentations of fascinating topics, or rather topics hat become fadcinsting when you present them! You are a great ambassador for biology, keep on educating and inspiring future generations. Another fantastic video! We all appreciate what you are doing Leslie.

  • you seem to be really working hard on these videos
    so really thanks
    my a2 biology exam is after 2 days and the stuff about the action potential was really helpful

  • @100100100509 Wow, thanks for that feedback. So glad that you are finding so much value in the videos. I will continue working to make it even better 🙂

    All the best on your biology exam. Let me know how it goes.

  • Wow, thanks for that feedback. So glad that you are finding so much value in the videos. I will continue working to make it even better 🙂

    All the best on your biology exam. Let me know how it goes.

  • Wow, thanks for that feedback. So glad that you are finding so much value in the videos. I will continue working to make it even better 🙂

    All the best on your biology exam. Let me know how it goes.

  • Wow, thanks for that feedback. So glad that you are finding so much value in the videos. I will continue working to make it even better 🙂

    All the best on your biology exam. Let me know how it goes.

  • I will, thank you for ypall your hard work. Even though i am not doing biology at uni i will watch every one f your videos over the summer hols as they are an absolute delight. Thank you!!!! Will let you know how it goes.

  • I will, thank you for ypall your hard work. Even though i am not doing biology at uni i will watch every one f your videos over the summer hols as they are an absolute delight. Thank you!!!! Will let you know how it goes.

  • the video was enlightening. my question is, what is the characteristic of lidocaine why it would stop or block the sodium ion channel.?

  • the video was enlightening. my question is, what is the characteristic of lidocaine why it would stop or block the sodium ion channel.?

  • @MrKubaron I’m not sure what the characteristic is that causes it to block it, but I do know that it blocks V-gated sodium ion channels in the open or the inactive state. I assume that it has to do with structure, but I can’t tell you specifically.

  • I’m not sure what the characteristic is that causes it to block it, but I do know that it blocks V-gated sodium ion channels in the open or the inactive state. I assume that it has to do with structure, but I can’t tell you specifically.

  • I’m not sure what the characteristic is that causes it to block it, but I do know that it blocks V-gated sodium ion channels in the open or the inactive state. I assume that it has to do with structure, but I can’t tell you specifically.

  • the video was enlightening. my question is, what is the characteristic of lidocaine why it would stop or block the sodium ion channel.?

  • I’m not sure what the characteristic is that causes it to block it, but I do know that it blocks V-gated sodium ion channels in the open or the inactive state. I assume that it has to do with structure, but I can’t tell you specifically.

  • hey i was just wondering about the deactivation gate and what charge it is? i dont really understand why it cant be opened again if it is positively charged would it not just repel again and then open?

  • @hannnahhhh1 I’m not sure what the charge of the deactivation gate is. What I do know is that it closes automatically after the opening of the activation gate. There has to be some kind of structural thing as to why it happens that way. It would be interesting to look at that further.

  • I’m not sure what the charge of the deactivation gate is. What I do know is that it closes automatically after the opening of the activation gate. There has to be some kind of structural thing as to why it happens that way. It would be interesting to look at that further.

  • I’m not sure what the charge of the deactivation gate is. What I do know is that it closes automatically after the opening of the activation gate. There has to be some kind of structural thing as to why it happens that way. It would be interesting to look at that further.

  • hey i was just wondering about the deactivation gate and what charge it is? i dont really understand why it cant be opened again if it is positively charged would it not just repel again and then open?

  • I’m not sure what the charge of the deactivation gate is. What I do know is that it closes automatically after the opening of the activation gate. There has to be some kind of structural thing as to why it happens that way. It would be interesting to look at that further.

  • Thank you so much . I’m medical student and now I’m studying about cardio system. Your knowledges help me slot

  • Hi, I don’t quite understand what my textbook Vander’s physiology 12th edition says: “When the membrane repolarises, the channel closes, forcing the activation gate back out of the pore and allowing the channel to the closed state..” What do they mean by “forcing the activation gate back out of the pore”? And why can we visualise it as a “ball and chain”? Any clarification would be great and thank you in advance! : D

  • Hi, I don’t quite understand what my textbook Vander’s physiology 12th edition says: “When the membrane repolarises, the channel closes, forcing the activation gate back out of the pore and allowing the channel to the closed state..” What do they mean by “forcing the activation gate back out of the pore”? And why can we visualise it as a “ball and chain”? Any clarification would be great and thank you in advance! : D

  • Hi, I don’t quite understand what my textbook Vander’s physiology 12th edition says: “When the membrane repolarises, the channel closes, forcing the activation gate back out of the pore and allowing the channel to the closed state..” What do they mean by “forcing the activation gate back out of the pore”? And why can we visualise it as a “ball and chain”? Any clarification would be great and thank you in advance! : D

  • @Roxrockereyl Hi! Unfortunately, Leslie’s been busy with so much work to be able to answer any of the inquiries he’s getting from the overwhelming emails he receives everyday. But, there are actually other videos on repolarization and sodium channels from the website at Interactive Biology, which you might find helpful. We hope you’ll find something from there. Thanks!

  • Hi! Unfortunately, Leslie’s been busy with so much work to be able to answer any of the inquiries he’s getting from the overwhelming emails he receives everyday. But, there are actually other videos on repolarization and sodium channels from the website at Interactive Biology, which you might find helpful. We hope you’ll find something from there. Thanks!

  • Hi! Unfortunately, Leslie’s been busy with so much work to be able to answer any of the inquiries he’s getting from the overwhelming emails he receives everyday. But, there are actually other videos on repolarization and sodium channels from the website at Interactive Biology, which you might find helpful. We hope you’ll find something from there. Thanks!

  • Thank you so much I was confused with inactive and closed, and now I understand it. Thank you!

  • hi, I am an egyptian medical student… i am fully surprized how biology can be so fun like this.. you are really great teacher
    i hope you teach me one day..and good luck with your work

  • hi, I am a medical student from egypt. I am really surprized how biology can be so fun like this.you are a great teacher .. i hope you teach me one day.and good luck with your work

  • hi , here is a question confusing me alot: how a memmbrane can be
    more pemeable to certain ions than others ?does it depend on number of channels or diameter of these ions? i hope you answer this

  • Yes, it has to do with the number of channels. For example, there are many more K+ channels in the membrane than Na+ channels. So the membrane will be more permeable to K+.

  • you are the best. thank you for sharing your knowledge and talent. you are a great teacher!!!

  • Thanx for all your video’s Lesley, they’re great! I still have one question for this video, can sodium ion’s travel trough the gate when it’s inactive?

  • I love your videos, and I find the box analogy really one of the most memorable explanations I have heard. Just a small comment, that the inactivation gate should be open during the closed state. Did you consider having the inactivation gate was on the bottom of the box so that the analogy would model the channel more accurately?

  • I’d love to see something on all the molecules that form the sodium pumps themselves. Most videos only talk about the sodium and potassium ions and refer to all other structures without mentioning their molecules.

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