007 What is an Action Potential

What is an Action Potential?

That’s the question I’m answering in todays Interactive Biology Episode. Watch the video above to find out 😉

This is the first in my new video format and I really hope you enjoy it.

Once you have finished watching the video, go ahead and leave your comments below.

If you have any questions, that would be the place to ask them.

– Leslie Samuel

Transcript Of Today’s Video

Welcome to another episode of Interactive Biology TV. My name is Leslie Samuel. In this video, I’m going to be answering one basic question: What is an action potential? You’re probably going to notice that it’s a little different than the 6 episodes that I’ve done before. And the 2 main differences that you’re going to notice are:

  1. I no longer call it BioVid. The reason for that is “Biovid” doesn’t really tell what this is all about. I’ve changed it to Interactive Biology TV, because it’s going to be interactive, it’s going to be about biology, and it’s going to be a video. So from now on, you’re going to hear me say “Interactive Biology TV” as opposed to “BioVid.”
  2. You’re going to notice that I’m on camera this time, and that’s a little different because in the past, I’ve done slides and animations and so on. The reason I’m making this change is basically because I wanted to do something that I can produce much quickly. In the last year, I only made 6 episodes, and I want to be doing episodes on a regular basis and this is just easier for me to produce and I can put together a relatively professional-quality video in a short period of time.

I hope you enjoy this new format. Please let me know in the comments below, and if you have questions or comments about it, you can just do that. It’s going to be relatively laid-back and I’m just going to be talking to you about these different concepts.

So, let’s get into the content for today. Today, I’m answering the question “What is an action potential?” If you’ve looked at any of the previous episodes, you’ve seen that I’ve given an introduction to the nervous system and to neurons. That introduction to neurons basically comes right before this in terms of understanding the concepts, the different parts of the neuron.

Now, the main part of the neuron that we’re going to be talking about today is the axon. I have a very amazing device here that I’m going to be using to illustrate that. The axon is the part that sends the signal. A signal starts in the soma, there’s processing that happens in the soma, and we’re going to talk about that later on. It sends a signal via the axon, to the ends of the axon, the axon terminals, and then that signal can basically go to the next neuron.

How I’m going to illustrate this is really simple. If someone touches your hand, you feel it. And the reason you feel it is because there are signals that start at that point, and the signals go to your spinal cord, and then up to your brain. These are electrical signals that happen relatively quickly, so that your brain can interpret that stimulation, and your brain tells you “Okay, someone is touching you.”

That is an action potential. You can call it an action potential, you can also call it a nerve impulse, but it’s basically that electrical signal that goes from that stimulation point all the way to the brain. And these signals are going on throughout the body, doing a bunch of different things, and we’re going to talk about that.

So, here we have my handy-dandy iPhone 4. I’m going to turn it on. And I have my earbuds, I’m going to put these on. I’m assuming you guys know how this works, but the iPhone 4 is an amazing device. It has built-in an iPod, and I’m going to assume you know what an iPod is. You know what, I’m going to tell you what an iPod is, just for some strange reason you don’t know what an that is. It’s an MP3 player that allows you to play music and audio books and a whole bunch of other stuff.

Anyhow, I’m going to stimulate this iPhone, and it’s going to send an electrical signal via this cable to the earbuds, and we’re going to assume as if it’s going to my brain. And it is going to my brain. So, here we have a cable sending signals, and then there can be a response. The brain can interpret that stimulation. Okay, so I’m going to press Play, and this is me stimulating. And as soon as I press Play, I can hear music. I can dance to the music, I can do a whole bunch of stuff. Let me stop that for now.

But basically, here we have that wire, and these are the axons of the neurons sending signals to the brain, to different parts of the body. It’s basically how the nervous system communicates with the different cells and organs and the glands. So, really simple, the action potential is that signal that goes through the axons along the nerves and basically takes a signal from one place to another place, whether that’s from the brain to my hand that pulls away, whether it’s from the stimulation point all the way to my brain.

I hope that makes sense for you. That’s basically what an action potential is. If you have any questions, comments, leave it below in the comments field. I’d be happy to follow up and answer your questions, or even make a video about it. That’s it for this episode, and I’ll see you on the next one.



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  • Leslie

    I like the new format. It is very clear and interesting. Thanks for continuing to do this.

    Mr. Khoury

  • Thanks for the Feedback Mr. Khoury. Glad you find it clear and interesting. I’ll be trying to post a video every weekday, so stay tuned!

  • loved your video, im very confused with compound action potential can you help me out with that

  • Hi Naqqiya.

    An action potential is what happens in an individual axon. Nerves are bundles of axons. In other words, there are MANY axons in one nerve. The compound action potential shows you the sum of all of the action potentials in all of the axons of that nerve. That being said, the more axons in the nerve that reach their threshold to result in an action potential, the bigger the resulting compound action potential. If all of the axons in that nerve are firing, you will have the strongest compound action potential.

    Hope that helps!

  • Thank you so much for this video. I FINALLY understand the definition! I hope I’ll be able to explain it back on the test.

  • I’m still confused on the action potential source. The membrane potential creates a local graded potential in a cell and when excitable cells recieve a stimulus they create an electrical action potential that travels from the stoma to the axon to the synapse?? Is this correct?

  • dude.. you are awesome….simple simple ….easy.
    I’m not a doctor or a nurse and i am not gonna be.(unfortunately or …!).
    but i had to take an anatomy class …and it is killing meeee…BUT YOU MAKE MY LIFE SO EASYYYYYYYYYYYYYYY.
    best of luck to you 😡

  • hey you did a great job. listen i don’t speak english very well but i have a question and i hope it will make sense
    when sodium ions go inside the cell and potassium.. does it happen through the sodium potassium pumb????
    i hope you answer

  • hey you did a great job. listen i don’t speak english very well but i have a question and i hope it will make sense
    when sodium ions go inside the cell and potassium ions go outside.. does it happen through the sodium potassium pump????
    i hope you answer

  • @ojay12341234 Thank you! Unfortunately, Leslie no longer have the time to go through all of the overwhelming emails he has been receiving. He’s busy with the site working on more Biology videos. So, please stay tuned!

  • @ojay12341234 I hope you ended up getting the information, but its quite a bit more difficult than just the sodium potassium pump. there are specific pumps that open during an action potential called “ligand gated channels”, “voltage gated channels” “mechanical gated channels and leaky channels. I’d advise looking into the ligand gated and voltage gated as they are the most important.. Feel free to message me if you want more information.

  • Seriously, you are great. You make it so clear! Textbook is ridiculous, wish I thought to look concepts on youtube early, but made it in just before my final! Thanks!

  • man you are super-duper cool teacher, that is what we all students need!!
    and your videos are really helping me a lot!! thanks a lot!

  • @punkvijay224 Thank you 🙂 Glad to know the videos are helping. Please stay
    tuned for more Biology videos to be uploaded to the site. have fun!

  • Thanks a ton for the video! Can I make one minor suggestion? For future videos, can you find a way to upload it with stereo audio? I only hear it in my left headphone (which is a bit of a distraction… but its a very minor inconvenience, still a great video).

  • thank you so much! I’m an old dude 50+ yrs. I wish I would have had someone like you for a teacher years ago. maybe I did but just didn’t pay attention….haha. keep up the Great work.

  • What a great video! I was confused about Action Potential on my lecture yesterday, I came to you tube for quick look and I found you.
    It was so clear, well presented and well described. I am gone go home now with smile knowing what Action Potential is after spending time by studying in library. Please keep it up ,to help student like me. God Bless you, u make my life a bit easier! thank you 🙂 oh! I also like your smile.

  • What a great video! I was confused about Action Potential on my lecture
    yesterday, I came to you tube for quick look and I found you. It was so
    clear, well presented and well described. I am gone go home now with smile
    knowing what Action Potential is after spending time by studying in
    library. Please keep it up ,to help student like me. God Bless you, u make
    my life a bit easier! thank you 🙂 oh! I also like your smile.

  • Leslie, thankyou so much for explaining biology so simply and easy to understand – your visuals and easy going manner make me feel less pressure about learning this stuff! Wish you the best!!

  • Ive just get my Human physiological proceses egzam results.
    There was a question about rest state of a neuron.
    What movment occurs during the rest state?
    What movments of Na and/or K.
    Ive marked that there is no movemnet at all. But the teacher said iam wrong. Could you please explain me this plzzzzzzzzzzz

  • You are AWESOME! I finally get what an action potential is–I will be watching the rest of your videos. Thanks again–may God bless you abundantly for taking the time to do this!

  • @Lynn1Fargo Hey I can answer :D, there is a K movement only because K ion channels are the only channels that remain opened during resting potential… so any change in the resting potential will depend directly on K..

  • Hey I can answer :D, there is a K movement only because K ion channels are the only channels that remain opened during resting potential… so any change in the resting potential will depend directly on K..

  • No offense but that was a over simplification of this concept. You said nothing about what drives an action potent and it’s functioning. How are you going to explain AP without even mentioning Na+/K+, voltage-gated channels, electrical excitability, etc.

  • @Caribbeanpearl09 No you know that the Na channels are stimulated by the voltage changes..The depolarization state will cause a difference in voltage, this will stimulate any nearby Na channels to open…K channels are slower than Na ones in closing, Na channels on the first end of Action pot. will wait for K channels to be closed, Na chan. won’t open even if there was a stimulus as long as K chan. are opened…This will cause the movement of Action pot. in one direction in the axon..

  • No you know that the Na channels are stimulated by the voltage changes..The depolarization state will cause a difference in voltage, this will stimulate any nearby Na channels to open…K channels are slower than Na ones in closing, Na channels on the first end of Action pot. will wait for K channels to be closed, Na chan. won’t open even if there was a stimulus as long as K chan. are opened…This will cause the movement of Action pot. in one direction in the axon..

  • @Caribbeanpearl09 simpler, at the first end of action potential Na channels have been opened once earlier…It won’t be opened again until the K channels closed…at the second end Na channels haven’t been opened earlier, think of them as virgins, so any change in voltage will open them, then Na chan. will be closed in the new area of the axon, K will open, Na will wait for them to close in order to be able to open again, virgins of the newer area will open…and so on and so on…

  • simpler, at the first end of action potential Na channels have been opened once earlier…It won’t be opened again until the K channels closed…at the second end Na channels haven’t been opened earlier, think of them as virgins, so any change in voltage will open them, then Na chan. will be closed in the new area of the axon, K will open, Na will wait for them to close in order to be able to open again, virgins of the newer area will open…and so on and so on…

  • Hi! We use your episodes in our cardiology class in Belgium! They are really helpfull, although in the beginning we thought our teacher was a bit lazy.. 😉
    Greetings!

  • i don’t think, that black ppl should think about things like that… come on… seriously… u should sell drugs or shit like that dog!

  • if you have a problem with black people, then hop off the vid. ignorant
    people like you NEED to DIE!

  • Please tell me apple are paying you for this! 😛
    Anyways, awesome vid, keep it up.

  • our teacher use this video’s for the lesson’s in the university. it makes the lesson’s more amusing 🙂 and it makes studying a little bit easier 🙂

  • our teacher use this video’s for the lesson’s in the university. it makes the lesson’s more amusing 🙂 and it makes studying a little bit easier 🙂

  • SO GOOD! I’ve found a video that makes learning this stuff easier. Thank you 🙂 Top shelf!

  • Hey,
    Awesome videos can you please do one on blood,red and white cells and plateletes

  • thanks for video but the explaination of action potential is more than what he said.

  • Glad I found your video because I couldn’t grasp the reading material and when I saw your video I then felt kind of like wow I can understand that LOL..anyways I look forward getting educated by your videos. 🙂 God Bless

  • Glad I found your video because I couldn’t grasp the reading material and when I saw your video I then felt kind of like wow I can understand that LOL..anyways I look forward getting educated by your videos. 🙂 God Bless

  • Dude, this is so great! Thanks a lot for putting so much time into all this. It’s so helpful!

  • you forgot the actual action potential with a sodium potassium pump

  • This guy is cool. Is it racist that I always think black people are cool?

  • studying for the AP bio exam and this is really helping me clarify a lot of stuff that weren’t as clear as before! thanks for these videos!

  • studying for the AP bio exam and this is really helping me clarify a lot of stuff that weren’t as clear as before! thanks for these videos!

  • Hi
    I really like your explanation in your videos you made everything complicated much easier for me. Please if you can talk about the cable theory of the neuron and the spatial constant and time constant and how the neuron works as a capacitor and resistor that would be of great help. I will take my PhD first level exam soon and I have some problems in understanding the cable theory of the neuron.
    Thank you so much

  • Wow, this is a really helpful video. I am in year 9, and I love science and want to go into the neuroscience side. You have helped me so much, and i appreciate it.

    Thank you!!

  • Wow, this is a really helpful video. I am in year 9, and I love science and want to go into the neuroscience side. You have helped me so much, and i appreciate it.

    Thank you!!

  • Thank you so much for uploading this! I have my end of semester exam on Tuesday next week and action potentials are something that have also proven to be a pain to try remembering but you have given me an easier way to remember!

  • Thank you so much for uploading this! I have my end of semester exam on Tuesday next week and action potentials are something that have also proven to be a pain to try remembering but you have given me an easier way to remember!

  • I think you’re brilliant. Thank you so much for giving this to the world.

  • Handy Dandy…….Iphone! (blues clues) lol ur so kool… ur vids make me excited about learning and are really helping alot my lecture professor seems more confused than me sometimes lol

  • Handy Dandy…….Iphone! (blues clues) lol ur so kool… ur vids make me excited about learning and are really helping alot my lecture professor seems more confused than me sometimes lol

  • simple, short, and using props, pictures, ect…. you did a great job and you made it seem fun not boring. it take 7 times to remember something so being easy to understand and fun helps

  • Your videos are very helpful. Just wondering why you don’t have a video for graded potentials or the differences between the two (action and graded potentials). Keep up the great work!

  • Get to the point! Too much dialogue explaining what you will talk about…it takes you almost 3 minutes into the video to answer the question.

  • The audio on this video is not working on my end. I do not know if I am the only one with this problem. Can you check to see what seems to be causing no sound on my end. Thank you.

  • It’s perfectly working on our end. You might want to check your settings and try it again.

  • just started physio and your videos are very helpful and you make concepts easier to understand (compared to my professor just reading off powerpoint slides)! Thank you!

  • Hi, just want to say I was really impressed by your presentation, I suggest you send some of your videos to TV broadcasters, I think you would be a really refreshing and inspirational TV Science presenter to lots of young people! Good luck and success with whatever you do…

  • omg u explain sooo well ! totally understood. i was having some trouble with the action potential !!!

  • thanks professor samuel. you are genius! i hope you can make a video about clinical and ontogenetical division of encephalon. thanks 🙂

  • can’t you put the sound on both speakers in sony vegas or something? it’s so annoying as I’m wearing headphones.

  • Too long before getting into what the video is supposed to be about. Halfway in I still didn’t under what an action potential is.

  • I had a Bio final tomorrow, and I was super stressed out because I didn’t know this, but thank you! You helped me a lot! Can you explain to me what sodium pumps are, and what role they play in this process?

  • I had a Bio final tomorrow, and I was super stressed out because I didn’t know this, but thank you! You helped me a lot! Can you explain to me what sodium pumps are, and what role they play in this process?

  • An action potential is generated by a sudden momentary increase in the permeability of the axon membrane to Na+ ions which enter the axon.

  • I would never in my life subscribe to a biology channel until I found you. Your methods or describing information is so entertaining to the point where I understood it! Thank you so much.

  • You…just made me understand a 90 minute class lecture…in 5 and a half minutes. O…M…G. My mind is blown.

  • wow ..so intrestin nd easy way to understnd action potential……or…music potential

  • I love you, you are the best. All your lectures are very clear to me 🙂 You have a way to make your lectures very easy to understand. Thank you

  • why cant you just shut the fuck up bro and start talking, gosh… what is action potential

  • How rude of you! You should be ashamed of yourself 🙁 If you don’t like it… move on!

  • Oh my gosh, I seriously want to take you home in my pocket! My husband might not mind!

  • Youtube should make a university using your videos. They explain way better than my lecturer and in less time as well! Thank you very much.

  • My lecturer’s notes and explanations are a mess, missing basic information and the notes not even referring to the meanings of some acronyms she uses. With my exam around the corner and none of what my lecturer says making sense i’m in a lot of trouble. Fortunately a friend pointed me to your videos which is really helping me out a lot and I could definitely use any help I can get.

    I really appreciate these videos as they’re of tremendous help. Thanks a lot!

  • Great videos, love how your aim is purely to teach instead of adding to much unnecessary information. I’m subscribed well done. And Thank you.

  • Thank you so much! Need more teachers like you. Love the easy to understand example.

  • Great channel. Great videos.
    I waswondering if this is the place to ask about LTP, NT, and in general some issues in neurophysiology.

  • Its just mono on my headphones… only the left ear works. Kind of Annoying, fix if if you can. but otherwise still awesome videos.

  • I love your videos. Thank you so much, you totally helped me through my veterinary medicine examns.

  • Its nt working here too… all the other youtube sound are working… only ur vid

  • I have sound on this video but it’s blurred, like only the bass is on…
    I’m watching a video under water, awesome!

  • Also, mine. It is only coming through on one channel. So if you have head phones or stereo speakers it should come through on one channel.

  • all videos have been very interesting……..keep up the good work frnd…cld u send me a video of the receptors of the human body.thank u

  • hey bra i jst wanted to thank u for your videos they are really helpful

  • Thank you so much for making these videos, they are so helpful! Wish you were my real bio teacher 🙂

  • THANK YOUUU FOR THE VIDEOO OMGGG
    it is so helpful 🙂
    i always like videos like this ^^
    please keep making more videosss!!!! 😀 😀 😀

  • How can I find the list or Playlist of related topic video in series so that i can move back and forth

  • This is a really simple video. You do not go through the sodium/potassium pumps, depolarization, refractory period nor resting state. This are core topics that average biology students would learn so please make videos about these.

  • . I have to train my mind to determine how I will interpret the signals I am receiving.

  • audio only working in one ear bud = action potential only travels through one of the axon terminals xD

  • thanks Mr Leslie,you made me understanding physiology easier than before.you’re such a great guy.thanks a lot

  • Amazing video, I had watch several videos about the same topic and it is kind of I rehearsed them without making any sense and relating the information to everyday activity, thanks for all the visuals you have used.

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