014 The Journey Down the Axon

[@InteractiveBiology]

@MsNany17 We're glad to know that you are finding value in our videos. Unfortunately, Leslie is no longer taking requests for specific videos, but he will definitely get to more topics in the future. He has many to work on at the moment. So stay tuned for more.

[@InteractiveBiology]

@shootingstars1511 That sounds nice, but it's not possible right now. If all I did was this, then maybe, but it's not. The best I can do is make the videos as I need them for the classes I teach. I will continue adding more, but since I'm just 1 person doing this for free, I can't do as many as you'd like.

[@MCxplained]

I spent 2 hours looking at different videos trying to find what i was looking for and nothing explained it the way I needed, your video did thank you!

[@InteractiveBiology]

@Emelyme Thanks for your comment. An action potential usually lasts around millisecond or less.

[@marccocke9924]

Your videos are a life saver! I really appreciate you taking your time to share these with those of us who are trying to navigate the A&P jungle!

[@InteractiveBiology]

@byerscha7015 Great question. When the Na+ crosses the membrane and travels downstream, remember that it's traveling by diffusion. As a result of that, it's basically spreading out, and the positive charge decreases. However, it's still positive enough to open more channels downstream and cause more Na+ to rush in. That of course gives more of a boost. Hope that helps!

[@87solovely]

Thank you, you have gotten me through both undergrad and grad school, thanks to your videos!

[@InteractiveBiology]

@aburmeis Oh gotcha. I remember that experiment. Here's the thing - If you stimulate it at the opposite end, you can be stimulating axons that have a different diameter. If the diameter is larger, that will have a higher velocity. If it's smaller, the velocity will be slower. The velocity will depend on the ratio of larger to small. One end might be thicker and the other end might be thinner. That's the only way that I can think that the velocity would be different.

[@shootingstars1511]

@InteractiveBiology i do understand , i should mention that i wasnt trying to attack you in any way or well "tell" you what to do .. it is hard to make videos especially that you are a teacher. thank you for what youve put up so far though :)

[@InteractiveBiology]

@acf431 You are very much welcome

[@dannichols6261]

Thanks for this, but I wish you had titled it something like the Journey of the AP down the axon, as I was looking for axonal transport of vesicles, and misunderstood initially what it was about from the title. But I do understand the work people put into these, and am grateful for that work.

[@InteractiveBiology]

@aburmeis Hi there. Thanks for asking the question. However, I'm not 100% sure what you mean when you say "whether or not you can put the nerve in either direction". Can you explain? Also, check out my video on Saltatory. That might help to explain what you are trying to figure out. It's episode 015.

[@InteractiveBiology]

@dhads420 That's great to hear :) THere are more Biology videos in the website that you may find useful. And, we have more coming soon! Have fun!

[@Emelyme]

U r a wonderful teacher. Thank you very much.... I had a question. How much time does it take for an actional potential to take place....??

[@marcusl.4404]

Hi, Mr. Samuel (hope I spelled your name correctly). I'm still in the early episodes of your series (great series, by the way) and I'd like to know, in the later videos, do you talk about neuroanatomy?

[@MilyAlcantar]

Why does the AP start in that part of the axon? I mean Why can't it start like in a Na channel that is in the middle of the axon and go from there on?

[@dannichols6261]

@Milagros, because the AP has to be stimulated by a sufficient voltage in order to open the voltage gated ion pores which would allow the AP to progress down the axon, and the axon hillock (or first segment of a myelinated axon) is where the signals (voltages from ions) from the dendrites accumulate (summate) in the soma to present to the axon. Those signals don't GET (directly) to the middle of the axon because it's too far away from the soma/axon hilllock/first segment. (I presume that by 'middle' you meant at a portion somewhere along the LENGTH of an axon, not a part INSIDE the 'middle' of a cross-section of an axon, as the events of an AP happen on/at the MEMBRANE of the neuron, not the interior.) And if you're concerned about axo-axonal synapses, those don't, as far as I understand, happen to the middle of an axon, but only at an axon TERMINAL, where one axon terminal synapses to another axon terminal, and modulates the exocytosis of neurotransmitters from that 'main' terminal.

[@InteractiveBiology]

@hupper12345 You're VERY much welcome!

[@InteractiveBiology]

@ligiabatista86 Glad to hear you are enjoying learning biology. It's fun stuff :)

[@InteractiveBiology]

@aburmeis Awesome. Glad to know that it helped :)

[@MsNany17]

I want an explanation for Supernomal phase & Subnormal phase in action potential .......PLEASE...... thank u 4 ur great efforts

[@USA01930]

you are the man great videos you saved my life!!!

[@InteractiveBiology]

@sketchybananas Yep, every single time!

[@jensicampos180]

Hi, I’m confused as to how the influx of Na+ causes the opening of more Na+ voltage channels down the axon. If the inside because more +, then why does it let more Na+ in? I get that it needs to carry on the action potential but… 😵‍💫😵‍💫 please help! Love the video btw!

[@InteractiveBiology]

That's a great question. The influx of Na+ opens the Na+ channels. This has to do with the structure of the channel. It has a positively charged "gate". So that positive charge pushes the gate open and since that allows more Na+ to rush in. It now has a pathway to enter.

[@ligiabatista86]

You make biology so much fun! xD

[@byerscha7015]

Great series but just one question: Those Na+ ions (positively-charged) rushing across to achieve Donnan equilibrium into a negatively-charged space *and* traveling in the direction towards the axon terminals are depolarizing the membrane and making it less likely for Na+ to cross the membrane "downstream" (towards the terminals) correct? I guess I'm struggling to see how this effect can continue propagating down the axon.

[@shootingstars1511]

@InteractiveBiology @MsNany17 it would be great to have one for what she suggested. in the end we are only suggesting , to make this channel the place to find everything,instead of having to go look for another user.. subnormal/supernormal is part of Action Potential. its like you cut out part of it.. if youre gonna explain 3/4 of it , might as well continue. nonetheless i love those videos. Great work.

[@howtomakemoneyeasy0]

Why doesn't the action potential travel backward? Please write the answer.

[@jgordin1982]

Can sodium traveling toward the soma move past channels in their inactive states (arp) and stimulate channels closer to the soma, thus getting a new action potential?

[@citytalkwithDJTOR3LL]

compare and contrast the propagation of electrical signals down the axon and transmission of signals across a synapse.

[@ruellalaylo6411]

What if the first sodium channel that was made open by an action potential was in the middle of the axon? Will it then be able to travel in two ways, since the sodium channel s before it is NOT in the refractory phase?

[@discordant8543]

Ruella Laylo I believe so, but I don't think that happens naturally.

[@annabelledavis4675]

hello, i have a question to ask if you dont mind, "Can you give three ways in which a neurone is similar to other animal cells

[@sketchybananas]

So this kind of thing happens everytime it's simulated? If it's not simulated what happens?

[@MilyAlcantar]

Thanx u so much for doing this i love your videos

[@InteractiveBiology]

@spicymeatsandwich umm, that's definitely something else.

[@InteractiveBiology]

@aburmeis Hope that's what you are looking for :)

[@Claire-wy2pd]

where are the voltage gated potassium channels repolarizing on the neuron?

[@InteractiveBiology]

They are all along the axon.

[@InteractiveBiology]

@jgordin1982 All questions are answered in the Interactive Biology community forums from now on. Go to the website in the description and then visit the community. This is to make it as efficient as possible as we have multiple people over there to help answer questions. All the best

[@hupper12345]

Thankyou!!!! :D