008 The All-or-None Action Potential

008 The All-or-None Action Potential

Leslie Samuel IBTV, The Nervous System 150 Comments

Ever wondered why people refer to the action potential as “all-or-none”?

Well, I guess you’ll just have to watch the video above to understand. In this video, I use the kitchen sink, a paper towel and marbles to bring the concept home.

If you have any questions/comments, feel free to leave it in the comments field below.

- Leslie Samuel

Transcript of Today’s Video

Hey, this is Leslie Samuel again and I’m kind of excited today. I just posted a poll on my blog, and it was for you guys to help me to decide what the subtitle or slogan for Interactive Biology will be, and the one that you guys decided on was “Making biology fun.” So this is the first time I get to use this introduction. Are you ready for it?

Hello and welcome to Interactive Biology TV, where we’re making biology fun! I like the ring of that. I wasn’t going for that title before, but when you guys suggested it, when you guys voted on it, it really started getting me excited.

Anyhow, in today’s episode, we’re going to be talking about the all-or-none nature of the action potential. We’ve been talking about the nervous system, and depending on which book you read, it might say “all-or-none” or “all-or-nothing.” Either way, we’re talking about the same thing. Now, there are two terms that I want you to know for this episode. The first one is the axon hillock, and the second would be the threshold, okay? We’re in my kitchen today, and I’m going to be using a high-tech device to illustrate these concepts. So, let’s look at what we have here today.

Alright, so this is my high-tech device for today. I’m not going to be doing any dishes even though we’re by the sink, but hopefully, this will get you guys to understand the concept of the all-or-none nature of the action potential. So the two terms I said were the axon hillock and the threshold. Axon hillock is the place where the axon starts. We looked at the neuron and the parts of the neuron, and right where it goes from the soma to the axon, we have the axon hillock. That’s the first place we see voltage-gated ion channels. In a previous episode, I spoke about the proteins in the membrane, and you can go back to that and see what these voltage-gated ion channels do.

But anyhow, this is where action potentials can start. However, in order for them to start, the stimulation needs to be enough to bring it to the threshold. So this, we’re going to imagine that this is my axon hillock, and in order for an action potential to happen, this needs to break, and when this breaks, voltage-gated channels open and ions rush in, and we have that electrical signal.

So, these are my ions, the little blue marbles, and I’m going to put the first one on here and nothing happens, that’s not enough to cause an action potential. I’ll put the second one and nothing happens. This is a pretty strong piece of paper towel. It’s Brawny, and I think that’s the one where you see a really strong man on the plastic wrap, so that should say something about the strength, I think.

Anyhow, I’m going to continue putting, still no action potential. It has not reached threshold just yet, so I’m just going to continue putting these ions. I’m trying to bring it to threshold, but it’s not there as yet. And we’re going to put some more. Evidently, Brawny is pretty strong. No insult against Bounty or any of those other paper towels. But here we go, I’m going to continue putting more stimulation, more stimulation, nothing happens. It’s pretty strong, so let’s dump some more on there. At a certain point, it’s going to reach a point where…

Oh! There we go . . . it breaks and those ions get through. That point was the threshold. Now, up until that point, nothing happened. But once we reached that point, we reached the threshold, it’s enough stimulus to cause the action potential to happen. That is why we call it all-or-none.

So there you have it, it’s all-or-none. It’s either going to happen or it’s not going to happen. If there’s enough stimulation to reach the threshold, as you saw with this elaborate set-up, if there’s enough stimulation, it will cause an action potential. If there isn’t enough, it will not cause an action potential. That’s why we call it all-or-nothing, all-or-none. I hope you enjoyed this episode. If you have any questions or comments, leave them in the comments field below. I’d be happy to answer your questions. Who knows, I might even make a video to answer your specific question. That’s it for this video, and I’ll see you in the next one.

Comments 150

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      Author
  1. Rafaela Marques

    Your videos are just great!!! I’m a medicine student and they are helping
    me a lot at my physiology classes. Thank you very much (:

  2. naqqiya

    is all or none potential same as difference between action and graded potential?
    Thanks and loved you video….u rock…!!!!

    1. Post
      Author
      Leslie

      Hi Naqqiya,

      Glad you loved the video. All or none simply refers to the fact that the action potential either happens fully or doesn’t happen at all. The graded potential is not an action potential.

      That has to do with the fact that we can get different levels of membrane potential change depending on the stimulus. If those graded potential changes add up to reach the threshold, that will cause an action potential.

      All the best!

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  3. InteractiveBiology

    @megaloveistheanswer WOOOHOOOOO. That is SUPER AWESOME! Congratulations on passing your Biology exam. I’m so glad that the videos have helped you, and I will continue working like crazy to deliver more value.

  4. Farzana

    Thank You SOOOOO much for making these videos. You are really helping me understand difficult concepts!! your the best!!

    1. Post
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  5. justanotheranatomystudent

    man, i have my anatomy test tomorrow, and I would not have been able to understand anything about how action potential works if it hadn’t been for your videos.

    thank you so much!

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      Author
    1. Post
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  6. DevX

    When you said Hi Tech device I thought it’s going to be an iPhone again ;)
    Anyway your videos are great keep it going keep them coming ;)

  7. InteractiveBiology

    @vestraya 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.

  8. EmpressLee75

    WOWWWW. Your examples are so clear, simple and direct. I enjoy listening to such an enthusiastic teacher, unlike my Uni lecturers. I was concerned about a test I have this coming Monday. I’ve been watching you for the last two days and I’m now looking forward to the test. Many, many THANKS to YOU. Blessings in ABUNDANCE :)

  9. jdillla93

    your videos are amazing. Im doing psychology & were currently learning about the CNS and the brain. I hated this and put it off for a whole week or two, im 19 and thats not good. I just want to say your practical videos & explaination is great. You really do make it fun ..well for me. im reffering everyone i know doing bio too you !

  10. jdillla93

    your videos are amazing. Im doing psychology & were currently learning about the CNS and the brain. I hated this and put it off for a whole week or two, im 19 and thats not good. I just want to say your practical videos & explaination is great. You really do make it fun ..well for me. im reffering everyone i know doing bio too you !

  11. toloveanatomy

    Wow! You are FANTASTIC! Your explanation is FANTASTIC! I wish you were my teacher!!!!! I am in love with you and your lectures!!!!!

  12. lynexeye

    Just like everybody, I would love to say too that Thank you so much. You are so helpful and easy to understand. Love your Videos… Please Upload more Videos about Different other Parts/Organs of the Body… Keep looking for your incoming videos..Loves and Regards from Pakistan <3

  13. AimeeleForain

    Thank you so much! You are so nice and everything is easy to understand! I am from
    Germany ;) keep up the good work!

  14. divoniarosemond

    love what you are doing but i have adhd so please stick to the subject and get to the point a little faster……. please i need you to pass my nremt exam !

    1. Post
      Author
  15. JanisRNdream

    Thank you, Love your stuff Only negative is adding in what kind of ions they are , sodium ions rush in.. I already knew but some may not know those facts, I subscribed and have a test on Monday 4 chapters so I will be watching you all weekend :)

  16. JanisRNdream

    Thank you, Love your stuff Only negative is adding in what kind of ions they are , sodium ions rush in.. I already knew but some may not know those facts, I subscribed and have a test on Monday 4 chapters so I will be watching you all weekend :)

  17. berryhouseful

    Could you please be my tutor? I would definitely get a 4.0! You are amazing..definitely gonna watch all your vids! Thank you! :)

  18. MHCOCC

    This was a great way to explain this concept-thanks for making this a very visual explanation-now I won’t forget the ‘all or none’ aspect!

  19. ai18able

    Peace be upon you Mr. InteractiveBiology :)
    can you make a video on mechanism of muscle contraction and relaxation?really hope you can help me.
    thank you! :)

  20. InteractiveBiology

    Hi! You’ll find Episodes 041 to 043 at Interactive-Biology about muscle contraction. Hope they’ll help. Have fun!

  21. Lisa Ledwidge

    Could you add in a note to the video on what you mean when you say “stimulus”? Thanks. Your videos are helpful! I like that they are short. I’m planning to recommend them to my A&P students.

  22. Lisa Ledwidge

    Could you add in a note to the video on what you mean when you say “stimulus”? Thanks. Your videos are helpful! I like that they are short. I’m planning to recommend them to my A&P students.

  23. SaraSiraj

    Thank you very much, I read my text book many times & couldn’t clearly understand the concept until I watched your video. Keep the amazing work & God bless you!

  24. SaraSiraj

    Thank you very much, I read my text book many times & couldn’t clearly understand the concept until I watched your video. Keep the amazing work & God bless you!

  25. blueBruSea

    Your video is amazing. What’s amazing is that a concept I had to reread multiple times was answered just by watching your video once. Great job with all the videos so far. They’re fun, interactive, easy to grasp, and concise. Thank you :D

  26. yasminhabibty

    Amazing, and I really mean it. Thanks a lot. I was moved by the creativity of this episode. Just like you hoped that we enjoyed this show. I thoroughly enjoyed it.

  27. missrej123

    Im learning a lot from your vids Sir. Im a nursing student and I stopped for a year, and Im refreshing my mind from the things that arent clear from me before. now I fully understand these things now:))) I will prepare myself from passing board exam;)

  28. RainbowxxMartini

    Thank you so much for picking up the slack of my bio teacher. He is so lazy and condescending. I’m so happy that I stumbled upon your videos! You are definitely helping my mark :)

  29. Barbi32105

    you are a very good teacher.. i like the method you use to teach.. i am going to take microbiology next semester i hope i can find more videos that can help me get a good grade =)

  30. Hyperiontje

    Hats off to you for answering every question out there. All your videos are very well structured and easy to understand difficult concepts. Big up!

  31. googke101

    Is that a Southern Adventist University water bottle by the sink?
    Mind = Blown
    I go to Union College, another Adventist college in Nebraska. Thanks for your videos!

  32. hristo hristov

    Hey guys. Nice film.

    My older brother had been obese. He went from 283 lbs of fat into 200 lbs of purely natural muscle mass. I used to be shocked. I just subscribed personally as I must greatly improve my overall physique. He used the Muscle Building Bible (Search on Google)…

  33. jkmissa

    this video is awesome. I laughed so hard when you talked about the big strong brawny man. You really do make biology fun!

  34. TheMysthicalWhore

    Hi I need an answer for question – what is the difference between AP in musle fibre (or nerve fibre) and whole musle (or nerve). I think, in the first case, it is about this law (all or nothing), and in the second case it is about summation of APs of each fiber?? But Im not sure…thank you! Silvia.

  35. Ali Stratton

    Hahaha! I love your paper towel jokes! Thanks so much for posting fun, interesting, and easy to understand videos! They are absolutely wonderful!

    God bless!!!

  36. Ghosty Coman

    Your home is gorgeous, by the by. Mine looks nowhere near so neat, even the corners that you probably didn’t expect to get videotaped, haha.

  37. Nikhil Thomas

    Yo yo… Awesome clip clip.

    My close friend was once a flabby. He went from 284lbs of pure fat into 217lbs of genuine muscle. I couldn’t believe it! I just joined personally coz I’m working to get stronger muscles. He made use of the Muscle Building Bible (Look in Google)…

  38. Nadinakin

    I got a question regarding the voltage threshold.
    Does a stimulus bring ions? Otherwise, where do the sodium ions that cause
    a rise in the voltage (to reach the certain threshold) come from? ?

  39. Nadinakin

    I got a question regarding the voltage threshold.
    Does a stimulus bring ions? Otherwise, where do the sodium ions that cause
    a rise in the voltage (to reach the certain threshold) come from? ?

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