The Schwann Cell and Action Potential

This video demonstrates the development of myelin in the peripheral nervous system and the propagation of action potential along a myelinated axon. The video was completed by Marziah Karch as her 2008 sabbatical project from the script and voiceover of Professor Marilyn Shopper.

This is close captioned, but in some cases a few of the words were left out to make it possible to read it at all.

Category:

Education

Tags:

• JCCC
• biology
• action
• potential
• neuron
• fluid
• mosaic
• model
• myelin
• axon
• Scwann
• cell
• CC

[PuraVid4]

@pirateXhunterXzoro Think of it like a train. The unmyelinated axon has 20 stations on its route and at every station it must stop and unload/load passengers. This slows down the total time the train is moving towards its destination.

The myelinated axon is a train with fewer stops. It only has to stop at a smaller number of stations (nodes of ranvier). This allows the the train to get to its destination faster.

[cjcurry222]

Now I understand, please teach my Professor, lol

[MrsPoker]

Nice, but no real explanation of why it's faster.

Comparing it to a train, or with 'tabs' instead of 'spaces' doesn't explain anything, it just makes it easier for the mind to accept.

[lonesomexheartbrokn]

@PuraVid4 Regarding @verosun12 's comment: Also, my textbook says that nodes of ranvier cannot be more than 1-2 mm apart b/c the cable properties of axons can only conduct depolarizations up to this distance.

[PuraVid4]

@verosun12 Theoretically yes but there would need to be a Schwann Cell large enough to cover the length of the axon. The Nodes of Ranvier are actually the junction between two Schwann Cells (myelin).

[lolajohnson1]

awesome

[mizhotmaplesyrup]

Beautiful, simple, ez to understand explanation w/ gorgeous animation! Wow!

[aznnaruto777]

I understand the train example above, but can someone explain in further detail? Like does the action potential start and end (resting) at each node and start again in the myelinated axon or does the influx of sodium in the axon keep the action potential from reaching resting state thus causing it to continually travel until it reaches the synapse? Or am I completely wrong?

[PiinoySolja]

music makes me want to fall asleep.

[Gugguggug]

This video is very good, but I didn't think it is clear on exactly HOW the myelin causes or transmits the signal from one Node of Ranvier to the next. Thanks.

[verosun12]

@PuraVid4 if the whole axon was covered in myelin would it travel faster since theres no stops?

[vikasbr94]

awesome video