Click Here to Download This Video
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.
About The Author Leslie Samuel
Leslie Samuel is the creator of Interactive Biology. He created this site to help Make Biology Fun and has the goal of making this the biggest and best biology resource on the net.
25. January 2012 at 11:00 pm
textbooks are for visual learners…
[Reply]
25. January 2012 at 11:00 pm
textbooks are for visual learners…
[Reply]
3. February 2012 at 6:39 pm
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
[Reply]
Leslie Samuel Reply:
February 4th, 2012 at 7:07 pm
So glad to know that the videos are helping you.
Stay tuned for more.
All the best!
[Reply]
4. February 2012 at 11:18 pm
You are awesome! Thanks!!!
[Reply]
15. February 2012 at 5:22 pm
i love your videos! u are a savior for making bio simple and easy to understand!!
[Reply]
16. February 2012 at 8:56 pm
thanks so much for these videos, these helped so much!
[Reply]
19. February 2012 at 3:04 am
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?
[Reply]
1. March 2012 at 12:13 am
u just saved me from disaster!!!
[Reply]
1. March 2012 at 12:13 am
u just saved me from disaster!!!
[Reply]
4. March 2012 at 3:22 pm
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!!
[Reply]
4. March 2012 at 7:02 pm
@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.
[Reply]
4. March 2012 at 7:02 pm
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.
[Reply]
4. March 2012 at 7:02 pm
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.
[Reply]
26. March 2012 at 1:11 am
finally understood!
[Reply]
26. March 2012 at 1:11 am
finally understood!
[Reply]
30. March 2012 at 3:39 pm
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.
[Reply]
31. March 2012 at 10:52 am
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.
[Reply]
6. April 2012 at 3:35 pm
My oh my, you are a gifted lecturer. I will show up for more of your vids.
Kind regards from good old germany.
[Reply]
8. April 2012 at 6:40 pm
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!
[Reply]
16. April 2012 at 1:32 am
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!
[Reply]
16. April 2012 at 5:50 pm
thank you for your videos they have helped so much
[Reply]
22. April 2012 at 1:14 pm
You, Leslie Samuel, are a king among men. Thank you.
[Reply]
10. May 2012 at 11:10 am
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
[Reply]