024 @Nicodube23 How Myelin Sheaths speed up the Action Potential

[2ManuBoy2]

Hi good video. i have a different way of thinking about why it speeds up conduction. basically in myelinated neurones the actional potentials only has to depolarise the nodes of ranvier and not the mylein sheath since the mylein sheath is impermeable to Na+ ions and node of ranvier are premeable. Therefore allows for saltatory conduction. However in unmyleinated neurons the action potential must depolarises the entire area of the axon. therfore resulting in slower conduction. is this right?

[bohdanmaks]

@2ManuBoy2

No, see, Na+ wouldn't 'need' to wait around to depolarise every Voltage Gated Sodium Channels in order, but would travel down the axon triggering all of VGSC's as the ions diffused along. What slows it down is that Na+ actually leaks back out in uninsulated areas, shortening the effectiveness of each action potential event, slowing down transmission despite the fact that more VGSC's are available to provide a Na+ infusion.

[yattrich49w]

Peculiar responses for this video once again.

[airfergz18]

hey, I really appreciate this! it helped me out a lot and I had the same type of question. I will watch episode 3 now. Do you also get into the CNS and PNS?

[InteractiveBiology]

@airfergz18 Glad to know that it helped :) Yes, there are more videos in the website at the Interactive Biology site. And, there are those focused on the nervous system touching on topics about the CNS and PNS... We hope you'll find what you need :) And, stay tuned because we have more coming soon!

[SpiralsHappen]

Consider the assault to our myelin sheaths by the globalist bankster and corporate controlled and corrupted criminal US political elite onto the American people today. In the form of Chemtrails that contain aluminum oxide and barium oxide. Fluoridated water and vaccines that contain mercury. GMO foods etc. The list of assaulting substances goes on and on. To dumb us down while they conspire to cull us all to a manageable number.

[dadalacks]

So, is it that the Na + moves down the axon following the negative charges distributed along the length of the axon?

[shuffle224]

Great video, that makes a lot of sense. Thanks for explaining it so well!

[zackboomer]

@InteractiveBiology hey, just something about terminology - in class our prof stressed that the sodium ions were not literally "jumping" from node to node, rather just moving very quickly. is this correct?

[InteractiveBiology]

@zackboomer Semantics my friend. He says moving quickly, I say jumping. We both mean the same thing!

[Djalitana]

I guess during the impulse travelling along the axon the strength of the impulse need to be kept the same. As we know that is an all-or-none response. so at each node of Ranvier (the no myolinated point the sodium channel will be widely open for sodium NA+ to get in the membrane. I would really like to c a clip about the absolute and relative refractory period. thank you so much.

[InteractiveBiology]

@Djalitana Hi, I see that you already found the refractory period video, so you should be good. In terms of suggestions about videos, I make them as I need them for my classes. That's all I have the time to do. I receive a lot of great suggestions, but unfortunately, I'm not able to do them unless they are relevant to my classes that I'm preparing for.

[emeskaykay]

@InteractiveBiology Hello. Thank you for your nice videos. I would like to state something which was not so clear from the video. Regarding conduction within the sheathed part of the membrane, it should be emphasized that this takes place at speeds comparable to the speed of light. ie: it is an electromagnetic disturbance (spike) in a medium.

[emeskaykay]

@InteractiveBiology (contd from prev post) The actual charged particles move extremely slowly. This electromagnetic disturbance (spike) dies out very quickly. The myelin sheath helps the spike last for a longer distance, but it will still eventually die out within a few millimeters, unless it is able to trigger a new spike.

[emeskaykay]

@InteractiveBiology (contd from prev post) A new spike cannot be generated until there is a gap in the myelein sheath, so that the spike can trigger an ion exchange which in turn triggers a new electromagnetic spike. In this way a signal is propagated. I emphasize again that the intra-sheath signal is virtually instantaneous. Most of the time is spend in the gaps.

[emeskaykay]

@InteractiveBiology (contd.) Thus the fewer the gaps, the faster the overall speed of the signal. On the other hand you cannot have too few gaps since there is a limit to how long the electromagnetic spike can propagate without decaying completely (even with the insulation). So there needs to be just the right number (as you mentioned) of gaps per unit length to optimize the speed of the signal. END

[InteractiveBiology]

@emeskaykay That was a LONG comment, but WELL worth it! Thanks for adding your two cents!

[ingelix]

The voltage gated ion channel density is much larger in nodes of ranvier than in unmyelinated axons. What effect does this have?

Is it really so that beneath the myelin sheat there are voltage gated ion channels? Isn't the myelin sheat there to reduce the leakage that occurs outside of the voltage gated channels?

[InteractiveBiology]

@ingelix You should watch my video on Saltatory conduction. That explains some of that.

[rushnl2e]

thank you!!!!

[cateb1]

Excellent videos :D thank you very much!! X

[lolipopcupcake]

Thank you very much!

[Flabmeister]

(continued) action potential to almost instantly jump between the nodes at about every 3mm, hence the overall speed of transmission is greatly increased. I hope that helps with any general confusion :)

[Flabmeister]

As I understand it, in unmyelinated neurones electrotonic conduction causes localised circuits of +ve ions between neighbouring V-gated Na+ channels (which relies on ion exchange between axon and extracellular fluid), causing them to open as the p.d surpasses the threshold potential and they open. However, in myelinated neurones, there can be no ion exchange under the myelin sheath, so localised circuits can only be established between adjacent nodes of ranvier, and it is this that causes the a

[krudolph2000]

(cont.) If that is the case, that would explain what happens in demyelinating diseases where the myelin is attacked but the neuron remains intact. if the myelin is destroyed, nerve conduction slows or stops. If the myelin is completely gone, perhaps the ions leak out through the leak channels (LC) that were previously covered, but it seems logical that the myelin might still cover the LCs but the capacitance is higher so electrotonic conduction slows. Any thoughts?

[InteractiveBiology]

@krudolph2000 When you put it like that, it makes even more sense. That would definitely cause an increased capacitance, and since it's more likely to hold the charge, there's more charge to travel, which would help the signal travel as quickly as possible.

[krudolph2000]

This relates to some questions I've had about neuron membranes (Mb). The Mb acts like an RC circuit ie input resistance (R) relates to the # of leak channels, diameter, length of the axon and the capacitance (C) relates to the circumfrence of the mb. and distance between inside and outside of the cell. Is it that the C of the Mb "holds" the ions along the Mb slowing their movement? So, myelin reduces the C by creating more distance between in- & outside of the cell so ions don't get stuck?

[MaxPayne909]

You mentioned the perfect balance between electronic conduction and the boosting effect of the V-gated Na+ channels make it go faster. Please explain how this "boosting effect" works. What is happening physically to make it go faster? What Nicodube23's explanation of the Na+ leak channels made sense, but I don't think that's the whole explanation for this phenomenon. If you know the answer please be very specific. My curiosity is killing me!

[InteractiveBiology]

@MaxPayne909 A lot of people seem to be curious about that. All that I know about the topic is in the video and in the comments below, including what Nicodube23 explained. Unfortunately, I don't have anymore to add.

[brukernavn1]

Thank you for a wonderful video! One question... Do potassium-ions play a role in this other than restoring the resting potential?

[InteractiveBiology]

@brukernavn1 You are very much welcome. Potassium is definitely involved in two ways:

1. It's involved in repolarization (it leaves the cell making it more negative). Check out my video on Repolarization.

2. The Sodium Potassium pump pumps 2 Potassium ions in for every 3 sodium ions it pumps out. This happens all throughout the action potential and is the reason why Potassium is more concentrated on the inside (generally speaking).

Hope that helps.

[pirateXhunterXzoro]

Wouldn't electrotonic conduction exist in unmyelinated axons? If so, it would make sense for unmyelinated to move faster since there is no myelin sheath preventing Na to enter. Therefore, there would be an endless amount of Na and the electrotonic conduction would not slow down.

[InteractiveBiology]

@pirateXhunterXzoro Yes, it would still exist. The myelin sheaths just gives it the perfect balance of electrotonic conduction and the boosting effect of the V-gated Na channels. In cases where the axons are unmyelinated, Voltage-gated channels are opened all along the axon, and that is slower. When one channel opens, that triggers the one next door to open. In addition to the speed benefits, it also uses more energy to open v-gated channels.

[pirateXhunterXzoro]

@InteractiveBiology So in other words, the Na traveling through the axon in myelinated is faster than Na gates opening one by one in unmyelinated?

[InteractiveBiology]

@pirateXhunterXzoro Exactly, because it's the perfect balance of gates opening to give a boost and saltatory conduction, which is super fast :)

[nicodube23]

@InteractiveBiology thanks for your reply to my question!! unfortunately, like pirateXhunter i wasn't quite satisfied with the answer since electrotonic conduction (the faster one) is present in both myelinated and unmyelinated neurons. upon futher reading, the explanation i found that worked for me was that the electrotonic conduction in slower in unmyelinated axons because the Na+ leaks out along the way (due to the lack of insulation), effectively creating a greater resistance. THANKS AGAIN!

[InteractiveBiology]

@nicodube23 You are very right there. That also plays a factor, and that was something I forgot about. Thanks for adding that bit of info to the conversation. You contributed value.