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015 Saltatory Conduction

The action potential travels rapidly down the axon. Why? Because of the process of saltatory conduction.

In this video, I talk about how that process works.

Question? Comments? Leave them below :)

- Leslie Samuel

Transcript of Today’s Episode

Hello and welcome to Interactive Biology TV, where we’re making biology fun! My name is Leslie Samuel, and in this episode, I’m going to be talking about saltatory conduction. We’re going to look at how this process is responsible for having the action potential move quickly down the axon.

We’ve been talking about the action potential, and we’ve shown that in order for an action potential to happen, voltage-gated sodium channels need to open. And once those voltage-gated sodium channels open, sodium ions rush in, causing the membrane potential to become more positive and initiating the action potential.

Now, there’s something that you need to understand here. The process of voltage-gated sodium channels opening is significantly slower than sodium rushing along the axon once it’s in the axon. So sodium moving along the axon happens much quicker than the voltage-gated sodium channels opening.

You can think about it like this: if you’re in your car, and you’re trying to get into your garage, you can do that really quickly. However, in order to get into the garage, you have to wait for the garage door to open. And it’s a similar concept: voltage-gated sodium channels need to open, and that’s a little slower than the movement of the ions along the axon. Keep that in mind as we look at the example that I’m going to give right now.

To illustrate this, I am going to step back all the way back here. What I’m going to do is I’m going to take 4 steps forward. And I’m going to just go 1, 2, 3, 4. Now, those were 4 very small steps, and I’m going to take 4 steps backwards now again. 1, 2, 3, 4, and I’m in the starting position. Now, what I’m going to do is I’m going to repeat the same process but I’m going to take bigger steps. 1, 2, 3, 4, and you can see I’m much closer to the camera. I’m going to do the same thing and go back now. 1, 2, 3, 4.

Now, which one of these is faster motion? Of course, you’re going to say the second time, when I took the bigger steps, I was moving significantly faster. If we look at the axon, and let’s just look at a picture of an axon right now. What you will see is that we have Schwann cells that cause myelin sheaths to wrap around the axon. What you will notice by looking at this is you will see that there are little spaces between the myelin sheaths. These spaces are called the nodes of Ranvier. At these nodes, this is where we have voltage-gated sodium channels and voltage-gated potassium channels, but here is where the channels can open and allow ions to come in.

Because these channels are concentrated in these nodes of Ranvier, these are the places along the axons where the channels are going to open to allow sodium to come in. Once sodium comes in, it can jump from that node to the next node very rapidly. And then when sodium comes in at this point, it can go from that node to the next node very rapidly.

In other words, it’s as if the signal is jumping from one node to the next node to the next node, and that causes it to go faster, because it doesn’t have to wait for voltage-gated sodium channels to open all along the axon. It’s just like I was showing before. When I took bigger steps, I moved significantly faster.

Saltatory conduction is like taking these bigger steps, jumping from one node to the next node to the next node, and that helps the action potential to travel significantly faster. I hope that makes sense. As usual, if you have any questions, you can go ahead and leave your questions or your comments in the comments section below, and I’d be happy to answer your questions. That’s it for this video, and I’ll see you in the next one.

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Leslie Samuel is the creator of Interactive Biology. His mission is to use this site to Make Biology fun for people all over the world.

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Leave An AWESOME Comment

60 Responses to “015 Saltatory Conduction”

  1. Bruceistheboss1017 January 18, 2011 at 11:40 pm #

    Very clear video! learning this in biology, this really explains what we’ve been learning

  2. Bruceistheboss1017 January 19, 2011 at 4:40 am #

    Very clear video! learning this in biology, this really explains what we’ve been learning

  3. InteractiveBiology January 19, 2011 at 5:36 am #

    @Bruceistheboss1017 That’s awesome Bruce. Glad I can help to clarify what you’ve been learning!

  4. InteractiveBiology January 19, 2011 at 5:36 am #

    That’s awesome Bruce. Glad I can help to clarify what you’ve been learning!

  5. InteractiveBiology January 19, 2011 at 10:36 am #

    That’s awesome Bruce. Glad I can help to clarify what you’ve been learning!

  6. nicodube23 January 26, 2011 at 1:19 pm #

    but why would the steps be bigger in myelinated vs unmyelinated axons? that’s the real question… what is the conceptual explanation for insulation increasing speed of conduction?

  7. nicodube23 January 26, 2011 at 6:19 pm #

    but why would the steps be bigger in myelinated vs unmyelinated axons? that’s the real question… what is the conceptual explanation for insulation increasing speed of conduction?

  8. InteractiveBiology January 27, 2011 at 1:00 pm #

    @nicodube23 Great question. I answered your question with a video. Check out the video I just posted – Episode 24. Hope that helps!

  9. InteractiveBiology January 27, 2011 at 1:00 pm #

    Great question. I answered your question with a video. Check out the video I just posted – Episode 24. Hope that helps!

  10. InteractiveBiology January 27, 2011 at 6:00 pm #

    Great question. I answered your question with a video. Check out the video I just posted – Episode 24. Hope that helps!

  11. LUNurses February 5, 2011 at 1:50 pm #

    Why would saltatory conduction occur as opposed to waiting for the next voltage gated sodium channel to open? What triggers saltatory conduction?

  12. mikebradlydavis July 28, 2011 at 7:05 pm #

    Leslie, you make my life better! I love you!

  13. InteractiveBiology July 28, 2011 at 7:06 pm #

    @mikebradlydavis LOL. Thanks. Glad I can make life better in some way ;)

  14. InteractiveBiology July 28, 2011 at 7:06 pm #

    LOL. Thanks. Glad I can make life better in some way ;)

  15. mikebradlydavis July 28, 2011 at 11:05 pm #

    Leslie, you make my life better! I love you!

  16. InteractiveBiology July 28, 2011 at 11:06 pm #

    LOL. Thanks. Glad I can make life better in some way ;)

  17. IHateSarsi August 6, 2011 at 8:26 am #

    Hmm so the Na+ that comes in from the channels in a previous node travels down thru the myelin to the next node very quickly right?

  18. IHateSarsi August 6, 2011 at 12:26 pm #

    Hmm so the Na+ that comes in from the channels in a previous node travels down thru the myelin to the next node very quickly right?

  19. juhidgenius September 4, 2011 at 3:31 pm #

    are the only ion channels working in the neuron?? whether it is saltatory or contiguous conduction..is it like we have less channels in the saltatory conduction??

  20. juhidgenius September 4, 2011 at 7:31 pm #

    are the only ion channels working in the neuron?? whether it is saltatory or contiguous conduction..is it like we have less channels in the saltatory conduction??

  21. InteractiveBiology September 5, 2011 at 6:37 am #

    @IHateSarsi It doesn’t go through the myelin, it travels down the axon.

  22. InteractiveBiology September 5, 2011 at 6:37 am #

    It doesn’t go through the myelin, it travels down the axon.

  23. InteractiveBiology September 5, 2011 at 6:38 am #

    @juhidgenius It’s not that you have less, but they are blocked by the Myelin Sheaths.

  24. InteractiveBiology September 5, 2011 at 6:38 am #

    It’s not that you have less, but they are blocked by the Myelin Sheaths.

  25. InteractiveBiology September 5, 2011 at 10:37 am #

    It doesn’t go through the myelin, it travels down the axon.

  26. InteractiveBiology September 5, 2011 at 10:38 am #

    It’s not that you have less, but they are blocked by the Myelin Sheaths.

  27. Bas September 8, 2011 at 6:17 pm #

    Hello Leslie, is there a decrease in amplitude while traveling down the axion? or do the nodes of ranvier act like a “traject amplifier”?

    if yes, becouse you explaned that the voltage-gated sodium channels are much slower, does that not influence the travel time down the axion to the axion terminals?

    • Lrsamuel September 9, 2011 at 6:37 am #

      Yes, the v-gated channels do act like little amplifiers at the Nodes of Ranvier. Yes, they are a little slower, but it’s a trade off between their relative slowness and the decreasing altitude of electrotonic conduction. Keep in mind though that slow is relative. We’re still talking about milliseconds here.

  28. NeedsAHardOne November 29, 2011 at 6:16 pm #

    OH!
    I’ve known that AP travels fastest in myelinated axons, and I was always told it was because it jumps from node to node.
    But FINALLY someone gives me a more thorough explanation.

  29. InteractiveBiology November 29, 2011 at 7:57 pm #

    @NeedsAHardOne Glad to know we’ve cleared that one out for you :) DO stay tuned! There are more fun Biology videos coming very soon!

  30. InteractiveBiology November 29, 2011 at 7:57 pm #

    Glad to know we’ve cleared that one out for you :) DO stay tuned! There are more fun Biology videos coming very soon!

  31. NeedsAHardOne November 29, 2011 at 11:16 pm #

    OH!
    I’ve known that AP travels fastest in myelinated axons, and I was always told it was because it jumps from node to node.
    But FINALLY someone gives me a more thorough explanation.

  32. InteractiveBiology November 30, 2011 at 12:57 am #

    Glad to know we’ve cleared that one out for you :) DO stay tuned! There are more fun Biology videos coming very soon!

  33. alexharrison101 March 4, 2012 at 11:25 am #

    this is brilliant – thanks. i couldn’t figure what it was about saltatory conduction that made it faster, but you’ve really helped!

  34. alexharrison101 March 4, 2012 at 4:25 pm #

    this is brilliant – thanks. i couldn’t figure what it was about saltatory conduction that made it faster, but you’ve really helped!

  35. Uchchash March 15, 2012 at 5:28 pm #

    it’s really simple…the myelin sheath actually prevents wastage of resources which would have been spent in formation of Na/K ATPase pumps all along the axon.During depolarisation,the Na+ conc just below the pumps gets really high and so by simple diffusion,they travel laterally along the axoplasm,wrapped in myelin,until it reaches adjacent Node and causes threshold.The behind node cant get depolarised since it’s in refractory period and resting potential hasn’t established there yet.

  36. Uchchash March 15, 2012 at 9:28 pm #

    it’s really simple…the myelin sheath actually prevents wastage of resources which would have been spent in formation of Na/K ATPase pumps all along the axon.During depolarisation,the Na+ conc just below the pumps gets really high and so by simple diffusion,they travel laterally along the axoplasm,wrapped in myelin,until it reaches adjacent Node and causes threshold.The behind node cant get depolarised since it’s in refractory period and resting potential hasn’t established there yet.

  37. afiste March 19, 2012 at 6:30 pm #

    I’m already falling for you!!! You definitely rock and makes life much easier!!!

  38. afiste March 19, 2012 at 10:30 pm #

    I’m already falling for you!!! You definitely rock and makes life much easier!!!

  39. Hasan Dilhan Bingöl May 4, 2012 at 6:58 pm #

    Thanks for your these videos, but I’m having really big troubles with the understanding of the physics part of the action potential and the other membrane stuff.What I mean is that I have some troubles about properties of the cell membrane.One of the properties of the membrane is that membrane is a capacitor to separate electrical charges and this feature affects its length constant and tau value.Therefore, it affects the velocity of the action potential along the axon.I guess my knowledge is so superficial for a medical student.I gave my e-mail adress. Could you help me about this problem by sending me an e-mail or making a video please ?

    • Leslie Samuel May 7, 2012 at 5:02 pm #

      Glad you are finding value in the videos. Unfortunately, I’m not able to answer specific questions due to time limitations.

  40. Donna May 17, 2012 at 12:08 am #

    I love the flow of the video and thank you so much your videos have help me greatly in A&P

    • Leslie Samuel May 17, 2012 at 2:03 pm #

      You are very much welcome. Glad the videos are helping you.

  41. ninjaofginga May 28, 2012 at 10:55 pm #

    WOW you make all these concepts soo much easier to understand. Thank you very much, its seriously helping with my study :) hope you’re getting paid the big bucks, cause you really are a talented teacher and communicator!

  42. ninjaofginga May 28, 2012 at 10:55 pm #

    WOW you make all these concepts soo much easier to understand. Thank you very much, its seriously helping with my study :) hope you’re getting paid the big bucks, cause you really are a talented teacher and communicator!

  43. sottroll June 2, 2012 at 1:42 pm #

    Wow, thanks! It really did make sense now.. Great work, your brilliant !! :)

  44. sottroll June 2, 2012 at 1:42 pm #

    Wow, thanks! It really did make sense now.. Great work, your brilliant !! :)

  45. ApparentlyNick June 3, 2012 at 7:18 pm #

    Thanks this helped a lot! A question: Why are there still nodes of ranvier, would the proces not be even faster if there was only myeline sheaths? So basically, what is the purpose of the nodes of ranvier, is it necessary to regenerate an AP repeatedly for some reason?
    Thanks a lot!

  46. ApparentlyNick June 3, 2012 at 7:18 pm #

    Thanks this helped a lot! A question: Why are there still nodes of ranvier, would the proces not be even faster if there was only myeline sheaths? So basically, what is the purpose of the nodes of ranvier, is it necessary to regenerate an AP repeatedly for some reason?
    Thanks a lot!

  47. kmarie923kb September 4, 2012 at 1:10 am #

    You are the best! I have been watching a lot of your videos and I feel well prepared for my huge exam tomorrow! Thank you!

  48. Luke Cutts September 4, 2012 at 6:48 pm #

    I have a question why and how does the action potential seem to “jump”.
    Thanks

  49. wendyhirschi October 13, 2012 at 9:28 pm #

    Now why can’t other teachers, who you pay lots of money in college classes, explain it that way!!!!! That is such a great way to explain it!!!

  50. Zoelis17 October 27, 2012 at 12:58 am #

    wow! you are really good..thanks

  51. anita November 13, 2012 at 6:38 pm #

    Thank you SO much! I love your videos and have recommended them to all of my classmates. You are making my life in anatomy & physiology SO much easier to understand.

  52. Duh Dun February 23, 2013 at 8:45 pm #

    A better example will be having a messenger travel the entire distance from point A to B versus, lighting beacons that are over vast distances but close enough to be seen from one another (like in LOTR where Gondor asks Rohan for help).

    Thank you this made much more sense than I have been taught in the past.

  53. christy benhaim April 6, 2013 at 11:02 pm #

    so simple all of the sudden!!

  54. apatty94 May 22, 2013 at 8:18 pm #

    you rock!

  55. Christina Kresge November 5, 2013 at 2:55 pm #

    I love u. I was so stressed about my lack of confidence on this chapter… Thank you so very much. I am touched by your kindness to share!

  56. Brittany November 7, 2013 at 2:40 pm #

    I second what anita said! I’ve recommended my students watch your videos as well to supplement what I am teaching in class. Keep up the great work!