011 Hyperpolarization: Last Phase of the Action Potential

IBTV, The Nervous System
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First there’s Depolarization, then Repolarization and finally – Hyperpolarization. Want to know what it’s all about? Watch the video.

It’s only 2 minutes and 33 seconds, but it packs a punch.

Any Questions or Comments? Leave them in the comments section below.

Transcript of Today’s Episode

Hello and welcome to Interactive Biology TV, where we’re making biology fun! My name is Leslie Samuel, as usual. In this episode, Episode 11, we’re going to be talking about the last phase of the action potential, and that’s called hyperpolarization. If you watched the previous two episodes, we spoke about the first two phases, depolarization and repolarization. Now we’re talking about the last phase, hyperpolarization. Where we ended off in the last episode, potassium was rushing out of the cell, because voltage-gated potassium ion channels opened, and potassium wanted to leave, so potassium is now gone.

Now, potassium, as it’s going out of the cell, it’s trying to reach its equilibrium potential, which is somewhere around -93 millivolts. The resting membrane potential is somewhere around -70 millivolts, so we’re going lower than that resting membrane potential, and that process is called hyperpolarization. In other words, it’s over-polarized. It’s overshooting the resting membrane potential and going even more negative towards the equilibrium potential for potassium, because that’s where potassium wants to be.

Now, once we start heading towards that really negative -93 millivolts, there’s another process that’s still happening in the background, and that’s the sodium-potassium pump. It’s still doing its work. If you remember what that is, from the episode where we talked about the channels in the membrane, the proteins in the membrane, the sodium-potassium pump pumps 3 sodium ions out, and it pumps 2 potassium ions in. What that does as it’s working is it brings that membrane potential right back around the resting membrane potential. That’s the end of the action potential.

So we have depolarization, repolarization, hyperpolarization, and then the sodium-potassium pump doing its job to bring it back to resting situations. That’s it for this video, and if you have questions, you can go ahead and leave them in the comments below. I’ll be happy to take a look at those and maybe even answer it in a video like this. That’s all for this video, and I’ll see you in the next one.

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action potential, hyperpolarization, na K pump, nerve impulse, nervous system, Voltage-gated potassium channels

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  3. Thanks so much for this! I was having trouble learning this stuff out of
    the textbook and your explanation was really clear and easy to understand.
    Fantastic!

  4. Thank You So Very Much!! This was Greekology when my Professor was teaching it. How awesome, I expect to pass this module have been really struggling with the first few, but I am glad I found you Samuel. You are so humble yet so smart and talented. May God bless your soul as you continue to help all those who need your help!!

  5. That’s awesome. I’m so glad that the video was able to help you understand the concept. Feel free to share it with your classmates 🙂

    Blessings to you!

  6. One of the best teachers I’ve ever come across! Amazing explanations and demonstrations…thank you 🙂

  8. Thank you that really helped!
    But I have a question I have been wondering about…
    Why do the Potassium ion channels remain open throughout repolarization and depolarisation? In a book i have been reading in, it says they remain open throughout.

  9. Potassium channels aren’t open during depolarization. They open during depolarization and they stay open until the Membrane Potential gets low enough. However, they do start closing during repolarization as the voltage decreases. It’s like this: High membrane potential – open. Low Membrane potential – Close. Check out the video on Repolarization.

  14. ‘During hyperpolarisation, membrane potential inside is less than
    -70mv.say about -72mv. it is then brought back to resting -70mv by sodium potassium pump.’my ques is, if Na-K pump starts working at hyperpolarising state, it should create more negativity inside (as it pushes 3 Na+ out in exchange of 2 K+ inside. thus creating more negativity inside).Then how does the pump brings back the potential to -70mv from -72mv??

  15. Thank you for making it visual with the marbles and plus signs. It really
    helped clarify my confusion =)

  21. How does pumping 3 Na out and 2 K in make the membrane potential more positive? Sounds like it would leave you with a -1 charge, making it more negative…..

  26. @AznViperXT Thank you! We’ll let Leslie know how much you appreciate his way of sharing knowledge with everyone 🙂 Stay tuned for more because there’ll be a lot more Biology videos coming very soon… Enjoy!

  29. @FantasyGrl317 And, thank you too for your support! 🙂 You can go to our website for more Biology videos that you might find interesting. We guarantee you, you’ll learn and understand concepts easily. Stay tuned for more!

  30. Thank you so much for this! I’m taking Anatomy & Physiology right now and we started the nervous system last week. I have understood everything until we got to Hyper-polarization. I couldn’t figure out how we were going from about -90 mV to about -70 mV (less negative, therefore more positive) by decreasing the number of positive ions. But after watching your video about Donnan Equilibtium and this one, I finally get it!!! This has really helped! Thank you sooo much!

  31. Thank you so much for this! I’m taking Anatomy & Physiology right now and
    we started the nervous system last week. I have understood everything until
    we got to Hyper-polarization. I couldn’t figure out how we were going from
    about -90 mV to about -70 mV (less negative, therefore more positive) by
    decreasing the number of positive ions. But after watching your video about
    Donnan Equilibtium and this one, I finally get it!!! This has really
    helped! Thank you sooo much!

  32. @hmelton1247 You’re very much welcome! We are glad to know that you found value on this video and was able to help out. Do come back for more because there are a lot more videos coming very soon! 🙂

  36. I understand that the pump brings 2K+ back into the membrane because too much K+ going out the cell membrane but not the part that 3Na+ going out and altogether increasing the membrane potential

  39. after watching i felt like killing myself for wasting my whole day and night trying to understand from the books this action potential and neurons. Mashallah God bless you dear. Thank you so much for helping 😀

  42. @BDdiva1 You’re very much welcome! We’re glad to know the videos have been
    able to help. Do stay tuned because we have more Biology videos coming very
    soon!

  52. @Jab1113 OH man I am sooo a visual learner and I didn’t understand the
    cacashit textbooks were talking about.

  53. fuck a text book whats the point of going to lectures when i cant fully understand whats going on you are the man keep doing what your doing

  54. fuck a text book whats the point of going to lectures when i cant fully
    understand whats going on you are the man keep doing what your doing

  65. Hey do you happen to know how the A-current is bought about and how it can be influences to change the rate of spike firing… thank you
    P.s revision tends to make me dislike neuro but you’ve reminded me of how much i love it .. so thank you 🙂

  66. Hey do you happen to know how the A-current is bought about and how it can be influences to change the rate of spike firing… thank you
    P.s revision tends to make me dislike neuro but you’ve reminded me of how much i love it .. so thank you 🙂

  69. Great stuff, I really enjoy.
    Why is this last stage called hyper(polarization; a continued decrease in the membrane’s potential), when hyperthermia is an increase in one’s body temperature. It would seem that it should be called hypopolarization, similar to hypothermia (decrease in ones body temp – decrease in the membranes potential). Does it have to deal with the fact that the membrane’s potential is calculated in respect to the extracellular fluid? Thanks!

  70. Great stuff, I really enjoy.
    Why is this last stage called hyper(polarization; a continued decrease in the membrane’s potential), when hyperthermia is an increase in one’s body temperature. It would seem that it should be called hypopolarization, similar to hypothermia (decrease in ones body temp – decrease in the membranes potential). Does it have to deal with the fact that the membrane’s potential is calculated in respect to the extracellular fluid? Thanks!

  71. Thank you so much for sharing your knowledge with us in an understandable way. I do have a question about the Ion channels in the plasma membrane. In your video you talk about the sodium-potassium pump. I remember learning about this when I took A&P about ten years ago. I am taking it again and in my book it does not mention this pump. Instead, it mentions the Mechanically gated channel which opens or closes in response to mechanical stimulation in the form of vibration. Just wondering why I have not read anything pertaining to the sodium-potassium pump in this 13th edition of Principles of Anatomy and Physiology by Gerard J. Tortora and Bryan Derrickson.

  72. Hmm that’s strange. Let me put that on my list of A&P books never to look at. Ok, just kidding (kinda).

    Not sure why it wouldn’t mention sodium potassium pumps. There are various types of proteins in the membrane of cells. Sodium Potassium pumps are just one of them. However, it plays a very important part when it comes to the Membrane Potential.

    Watch my video on the Ion Channels in the membrane.

    Hope that helps!

  73. thank you , for helping me to understand the stages better.

    Q; the inside of the cell aslo contains proteins and negatively charged ions( does that have something to do with action potential?) My teacher wrote this on our notes but did not futher explain
    .

  75. Ok, my bad, the sodium potassium pump is mentioned briefly in two sentences. I went back and read again today. Thank you for your videos, they help so much!

  76. thank you , for helping me to understand the stages better.

    Q; the inside of the cell aslo contains proteins and negatively charged ions( does that have something to do with action potential?) My teacher wrote this on our notes but did not futher explain
    .

  83. Seen all of your videos about CNS all the way up to this point, your enthusiasm and perspectives have really helped me visualize biology of this sort on a new scale! keep it up your the best

  91. thank you!!! very helpful video.
    Is it correct to say then that the sodium pump is always working away in the backgound or just when there is an action potential?

  92. thank you!!! very helpful video.
    Is it correct to say then that the sodium pump is always working away in the backgound or just when there is an action potential?

  96. Thank you so much!! I couldn’t quite grasp the concept until I saw you use the white plus signs and the blue marbles. I feel much more confident about Membrane Potentials now!!

  97. @Zer0PvM Textbooks are so dull and hopefully will become redundant soon. Visual learning is better because it sticks in the brain better. And yes lectures are useless i dont even know why I bother because i learn nothing. Thank God for good online teachers like this young man. Life saver.

  98. Textbooks are so dull and hopefully will become redundant soon. Visual learning is better because it sticks in the brain better. And yes lectures are useless i dont even know why I bother because i learn nothing. Thank God for good online teachers like this young man. Life saver.

  99. Textbooks are so dull and hopefully will become redundant soon. Visual learning is better because it sticks in the brain better. And yes lectures are useless i dont even know why I bother because i learn nothing. Thank God for good online teachers like this young man. Life saver.

  100. Thank you so much!! I couldn’t quite grasp the concept until I saw you use the white plus signs and the blue marbles. I feel much more confident about Membrane Potentials now!!

  101. Textbooks are so dull and hopefully will become redundant soon. Visual learning is better because it sticks in the brain better. And yes lectures are useless i dont even know why I bother because i learn nothing. Thank God for good online teachers like this young man. Life saver.

  107. Please, I do not understand how hyperpolarization gains net positive charge (to return back to resting potential) when the sodium potassium pump gives out 3 Na+ ions for every 2 K+ ions taken in.

  108. Please, I do not understand how hyperpolarization gains net positive charge (to return back to resting potential) when the sodium potassium pump gives out 3 Na+ ions for every 2 K+ ions taken in.

  109. Ah nevermind. Hyperpolarization; sodium voltage gate’s inactivation gate closes, therefore decreasing Na+ permeability while K+ permeability increases. A net loss of K+ and positive charge by the cell is induced then.

  110. Ah nevermind. Hyperpolarization; sodium voltage gate’s inactivation gate closes, therefore decreasing Na+ permeability while K+ permeability increases. A net loss of K+ and positive charge by the cell is induced then.

  112. My oh my, you are a gifted lecturer. I will show up for more of your vids.
    Kind regards from good old germany.

  113. You have taken the complicated activities of the body and broken them down to plain simple processes. Without a doubt the most informative teaching/instruction I have ever received!

  114. You have taken the complicated activities of the body and broken them down to plain simple processes. Without a doubt the most informative teaching/instruction I have ever received!

  115. What amazing videos! I’ve watched all of the action potential videos after trying to understand this concept by listeing to my class lectures, reading my notes and text book and looking at the diagrams. I find your videos and ten minutes later I’ve got it! I’m in a 200 level college bio class! I’ll be telling my class mates about this video for sure!

  116. What amazing videos! I’ve watched all of the action potential videos after trying to understand this concept by listeing to my class lectures, reading my notes and text book and looking at the diagrams. I find your videos and ten minutes later I’ve got it! I’m in a 200 level college bio class! I’ll be telling my class mates about this video for sure!

  121. Your videos are incredibly helpful! Thank you. I do have a question though. Can the Potassium ions move before the Sodium ions or do the Sodium ions always move first? My notes seem to suggest that the potassium is switching first, as it shows a trough in the millivolts graph before the peak as Sodium rushes in, rather than after it.

    Many thanks

  122. Your videos are incredibly helpful! Thank you. I do have a question though. Can the Potassium ions move before the Sodium ions or do the Sodium ions always move first? My notes seem to suggest that the potassium is switching first, as it shows a trough in the millivolts graph before the peak as Sodium rushes in, rather than after it.

    Many thanks

  125. You are exactly the guy that I was expecting to make a website and channel in youtube named “Make Biology Fun”. You are perfect. Congratulations. I hope all my teacher be like you.!!!!!!!!!

  126. You are exactly the guy that I was expecting to make a website and channel in youtube named “Make Biology Fun”. You are perfect. Congratulations. I hope all my teacher be like you.!!!!!!!!!

  127. Hi the videos are really good it help me lot , but i have question what is refractory period

  131. At the Interactive Biology website, you’ll find a “contact me” page where you can send Prof. Leslie Samuel a message. Thank you!

  134. I AM STARTING TO HATE MY LEACTURER!!! Watching these videos are so much easier and clearer!!!

  139. i never thought i would be able to understand this until i watched your videos u are a legend!

  141. Thank you so much for this! I’m studying for my A&P final and I was struggling with this part. I had an “Oooooh! I get it!” moment while watching this. Thanks again! 🙂

  144. Thank you! Thank you! Thank you! Thank you! You cleared everything up! I didn’t even have questions lingering in my mind after this video! Great teaching skills!

  145. I am so greatful for your videos! You have a great way of explaining difficult subjects!

  146. This is what all my college professors are missing in their lectures…teaching with a smile on their face! thanks for the video!

  149. Thank you Professor. I watch your videos over & over for my neurology class. I like that your videos break concepts down into bit sized pieces.

  153. this is sooo amazing and well explained!! I have hope that I’ll pass my course now!!

  156. What happens if you have hyperkalemia, how does it affect the action potential??

  157. Wow I was staring at a lecture slide for 15 minutes trying to get my head around this chart im looking at with depolar, repolar etc. Shoulda saved my 15 minutes and come straight to you now it makes sense!! Cheers mate.

  160. I love your patience and how you relate to the slow process of AP and BIology student brains, in the words of oliver twist, may i have some more sir, please.

  161. WOW! Life seems a lot easier. I had so mush trouble understanding all these re/de/ hypo /polarization. Now I am sure wake me up in the middle of the night I will be more than happy to tell you all about them:)) THANK YOU SO MUCH!!!

  162. If 3 sodium ions go out and 2 potassium ions go in, wouldn’t the end result be negative? So wouldn’t this push the line further below the resting state?

  164. can u kindly give information on AFTER DEPOLARISATION,AND EXACTLY FROM WHICH POINT OF REPOLARISATION DOES THE RELATIVE REFRACTORY PERIOD STARTS AND ENDS

  165. Ok. Hours in lectures and could not understand this. 15 minutes watching your videos and now I understand. THANKS!!!

  168. Hi Leslie, can you please explain to me how the sodium potassium pump works? I have an exam on the 18th of December and one of the topics is on the action potential and neurons.

  170. Hi Leslie,

    Thank you SO much! I have not for the life of me been able to work out action potential and the depolarisation, repolarisation process until right now! Your videos make what I’m sure is a very complicated process, seem so simple and easy to understand.

    Thanks for doing what you’re doing and making it fun : ). There are definitely a lot of people benefiting from your knowledge.

    Really appreciate it.

    Ellie

  171. Thanks for such a session. Its one of the best and easy to understand format I ever experienced, I always prefer the books like Buchanan, Lehninger for these topics but your videos are quite more simpler to grasp the concepts and I am really happy that through such ways advance molecular cell biology and membrane dynamics’ study should’nt be a bourden for a learner. A sincere thanks to you Leslie.

  172. Regarding the polarization of a neuron, when there is a reduction in membrane potential relative to resting membrane, would you call that hyperpolarization or depolarization? I have a text that calls it depolarization, but from my perspective it would seem they meant to say an increase in membrane potential relative to resting membrane since resting is a negative value (approx -70 mV) and a reduction would, in my opinion, mean even more negative making it hyperpolarized. Am I misinterpreting the statement?

  173. @Mark Anthony .Ramos
    its been ages that you asked this question. Surprised that no answer is posted yet. You may found it out but for the others who ask the same questions, answer lies in the fact that K+ has a diffusion potential through its leaky channels. While this whole process is going on and Na+/K+ ATPase is doing its job, K+ is regaining its equilibrium potential. More negativity inside helps some of the escaped K+ to  renter the cell down the electrical gradient. I hope this explains your intelligent question

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