Factors affecting the speed of an Action Potential: The Speed of Conductance Along an Axon.

There are three factors that affect the speed of conductance:
Myelination and saltatory conduction
The diameter of an Axon
The temperature
Watch the video to find out how and why.
** 1.24min corrections- the myelin sheath in a Schwann cell is a lipid.
For past paper questions linked to this topic click these links.
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[@drhaneenali]

thank you so much Miss Estruch!! I've just started learning the nervous system so this was perfect timing :)

[@MissEstruchBiology]

Ah amazing timing 🙌 Hope it helps you. I have another 3 or 4 videos in the topic 6 playlist on the nervous system you may find helpful. kzbin.info/aero/PLOfYYgIrtVMhMzU-UpZbHJrGAnFIn2ArB

[@girishravi6731]

Hiya, I just wanted to point out that this was part of the playlist for unit 8, anyways thank you very much for the videos! They're really helpful and I really love the way they are set out and formatted!

[@MissEstruchBiology]

Hello Glad you liked it. Thanks for pointing that out to me, I've swapped it to topic 6 now 😊

[@Wasteman365]

Where the music at 😨

[@sebwilliams4677]

hi ive got a question, so when the first node of ranvier is depolarised, does the local electric charge/Na+ ions travel through the membrane to the next node to be depolarised? everyone says the impulse jumps so not sure if that means the local electric charge/Na+ ions jump between nodes outside of axon membrane?

[@MissEstruchBiology]

Hello, Great question! It jumps outside. The parts of the axon covered by myelin sheath will remain at -70 mV or resting potential continually. Only the nodes will vary in membrane potential.

[@raman7095]

Do we need to know this for OCR A?

[@markdean6174]

Thank you

[@MissEstruchBiology]

You're welcome 😊

[@solomonmarshall7851]

Thanks For The Video! I know you must not have time to answer every question- but I'd appreciate if you could do this one! If you have a wider Axon Diameter, the axon will have a higher surface area. If the axon has a larger surface area- then surely there would be more ions leaking through the plasma membrane. Unless we are talking about less leakage per unit volume of axon due to SA:V Ratios.. but if the depolarisation during action potential is localised, i don't see how this would have a significant effect. If we ignore that for the moment- is the reason action potentials travel faster, due to a lower potential difference between the inside and outside of the neurone- and therefore having a higher range of influence, and effecting more voltage-gated Na+ channels?

[@solomonmarshall7851]

I Also looked into Khan Academy's explanation- which I assume is uni level, and it talked about how in wider axons, Na+ have more pathway options to travel down the neurone thwt don't involve cellular collisions,, and contribute to the active potential. While this is likley beyond our specification- I'm curious as to why the explanations are so different

[@solomonmarshall7851]

...Unless.. it is that offers less pathways for the Na+ ions to collide with The plasma membrane and Na+/K+ pumps In the membrane membrane, and thus less Na+ ions are lost?

[@solomonmarshall7851]

Wow that was a brain teaser and a half

[@solomonmarshall7851]

I'd appreciate your thoughts 😅

[@MissEstruchBiology]

hey its partly due to SA:V ration but also due to less resistance in the movement of ions (just like in physics when learning about wires in electricity)

[@Fadibiology]

Thank you..question please, if u have two axons, the first one mylinated but has small dimeter, the second non-mylinated but has wider diameter, which one will be faster?

[@MissEstruchBiology]

ha ahh good question! You'd need to experiment to see, no set answer. Depends on exact diameter I guess. I would predict being non-myelinated would be slower

[@Fadibiology]

@@MissEstruchBiology thanks alot, that means we cant generalize that the myelinated axons are always faster ? Regardless the diameter is wide or small?

[@chinrxhh6707]

Hello,Miss Estruch.I wanna ask why wider diameter will not leak the ions out?And if the ions leak,where will the ions leak to?

[@Charlotte-pd2wl]

Ions would leak into the tissue fluid surrounding the neurones

[@Allahkimuhabbat]

👍