011 Hyperpolarization: Last phase of the Action Potential

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.

- Leslie Samuel

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.

169 Comments

  1. qymj October 2, 2013 at 1:08 am #

    Thank you so much

    Reply

  2. Chilakala pavan October 7, 2013 at 2:03 pm #

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

    Reply

  3. Stephanie Conley October 8, 2013 at 10:26 am #

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

    Reply

  4. nathanb605 October 14, 2013 at 8:12 pm #

    love this man

    Reply

  5. DrAbd El-RaHmAn November 16, 2013 at 6:18 pm #

    you great man
    i love watch you and really i understand all thing from u

    Reply

  6. Daphne Clarke December 12, 2013 at 4:08 pm #

    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.

    Reply

  7. towfiq December 14, 2013 at 12:07 pm #

    you make biology so easy for me
    can you explain to me what the sensory taste pathway is?

    Reply

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