011 Hyperpolarization: Last phase of the Action Potential

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.

199 comments
Todd
Todd

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?

Vaishali Purohit
Vaishali Purohit

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.

Ellie
Ellie

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

towfiq
towfiq

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

Daphne Clarke
Daphne Clarke

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.

DrAbd El-RaHmAn
DrAbd El-RaHmAn

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

Stephanie Conley
Stephanie Conley

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

Chilakala pavan
Chilakala pavan

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

qymj
qymj

Thank you so much

Mark Anthony .Ramos
Mark Anthony .Ramos

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?

Tina46796
Tina46796

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!!!

Nathalie Cladera
Nathalie Cladera

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.

Marbelis Morejon
Marbelis Morejon

thank you so much...everything is clear now ... amazing ;)

JJvideoman
JJvideoman

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.

Linda Holder
Linda Holder

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

chocolateddy22
chocolateddy22

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

mmiracleofGod
mmiracleofGod

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.

Maria Kukushina
Maria Kukushina

great job, thanx a lot:) watching you for two hours b4 test

russtery89
russtery89

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

Judith Koerselman
Judith Koerselman

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

DAHRealTrump
DAHRealTrump

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!

Abbigayle Brown
Abbigayle Brown

These videos have helped me so much! Better than any textbook! Thankyou.

Beth Botwin
Beth Botwin

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! :)

LivingOracles
LivingOracles

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

Tim Hernandez
Tim Hernandez

Thanks a ton, that makes makes so much more sense now.

SplashFlip
SplashFlip

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

mathelida
mathelida

ohh guys!! he is not replying...and i want soon :(

mathelida
mathelida

oh thank you so much ! .. :)

InteractiveBiology
InteractiveBiology

At the Interactive Biology website, you'll find a "contact me" page where you can send Prof. Leslie Samuel a message. Thank you!

mathelida
mathelida

can anybody tell me..?how to directly contact with Mr.leslie samuel??? thanks

NiMI
NiMI

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

MrKwnnos
MrKwnnos

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.!!!!!!!!!

teabag5
teabag5

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

Foinnse
Foinnse

You, Leslie Samuel, are a king among men. Thank you.