012 The Absolute and Relative Refractory Periods

[@weirdpride]

That was so well illustrated and explained. This is the exact explanation I needed, thank you!

[@peterkwolek2265]

You are an incredible teacher, thought I was going to be lost at first based on not knowing all the science terms but you explained everything so well.

[@InteractiveBiology]

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[@NightWanderer01]

A refractory period simply refers to the time frame in which the generation of further action potentials may be hindered (RRP) or may not occur at all (ARP). Hyperpolarization, in contrast, describes an event where the cell's membrane potential drops to levels below its resting potential due to excess K+ leaving the cell. However, it would be correct to say that hyperpolarization could occur during the RELATIVE refractory period (RRP). Hope that helps!

[@warpedoctave]

ive read guyton a couple of times, for hours on end and it finally made sense watching this video, God Bless thanks......... : )

[@TheAbsoluteTruthzz]

During repolarization Na+ channels close and K+ open causing an efflux of K+ and an overshoot of below -70mV. Sodium potassium pump and leak channels are working in the background to re-establish resting potential.

[@InteractiveBiology]

@2Aboody Glad we were able to help. Please stay tuned for more Biology learning and fun. We have more Biology videos to be uploaded very soon!

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[@raneembashar3394]

Iam studying medicine and this video really help me in my studying thank you alot 💚🙏

[@InteractiveBiology]

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[@MMAFAN21]

Awesome video. I'm a new paramedic and this really a great refresher. Thank you, I'm def subscribing

[@naghmetalakoub4089]

This helped me a lot I was so confusef. Now every thing makes sense Thank you

[@chriscrumbley9219]

Thank you so much! I just couldn't wrap my brain around it until I saw this video!

[@alphaWAYNE]

Thank you so much for making these videos... You make biology more fun, easy and very understandable... You are a great teacher. A million thank yous.

[@asseel70iraq99]

Still alive my man?😂😂😂😂😂

[@InteractiveBiology]

@katelayt Well, I'm glad I can help. All the best with your class!

[@rhiannonbreezesturgess9870]

So helpful, thank you so much for posting these videos! A&P would be killer without you!

[@darkscienceyt]

Superb explanation!

[@InteractiveBiology]

Thanks. Glad to help 👍🏽

[@LucifersCounterpart]

the day just smiled at me :D this is the best channel i hav my physiology exam in 2 days n i couldnt understand certain things before finding this channel but as i said grrrrrr8 channel ;D

[@InteractiveBiology]

@crackowacko87 No, the relative refractory period is longer. It starts at the peak of the action potential and continues until the resting membrane potential is restored. Hope that helps!

[@redblueweronika]

10 years later, still an awesome video!

[@ThePhenom94]

MAN THANK YOU! That was so easy and you explained it better than my teacher! ThankYou!

[@bashag5477]

This TOTALLY made sense! Thank you

[@InteractiveBiology]

You're welcome

[@pramvirrathee1751]

5:42 its wrong. Na channels are not closed, but inactivated. You can not use them again until Membrane potential reaches resting potential.

[@NaziFaa17]

BEST TEACHER EVER!

[@InteractiveBiology]

@lindaandjeffsampson Thank you :) Glad to know you appreciate this. There are more Biology videos in the website that you might want to check out. Stay tuned for more new videos! :)

[@bananapete]

No, the refractory period and the hyperpolarization are separate events that overlap. This graph could use 2 more variables: % of Na channels open; and % of Na channels inactive. You would see that as the AP starts to spike most of the channels go to open, then around the peak most of the channels go to inactive. The relative refractory period actually starts as the voltage is coming back down from the peak as Na channels transition back to closed and ready.

[@xwld2971]

Wow, thank you so much for making this easier! I'm really struggling with psychology. Keep making videos!

[@InteractiveBiology]

You are very much welcome, Carl.

[@shanzahiqbal3517]

Me too

[@DavidGreybeard]

This graph might be confusing. The refractory period labelled in the chart is what is called hyperpolarization. I'm not 100% sure but I think the refractory periods are over at that time and the reason why it takes a stronger signal to reach an action potential in a hyperpolarized membrane is because the cell is more negative than normal and takes more sodium ions to reach the threshold. It sounds like the refractory periods have more to do with the voltage gates resetting rather than the charge of the cell.

[@Anne-cc4hn]

yes abt the first remark ! but maybe its not his own graph but for his explaining is convincing

[@004aayushsharma7]

I am very happy to see this video love from 🇮🇳India (my lovely country)

[@mypassioninspiration]

Thank you, Mr. Samuel! You make me confident to get an A for my class! I really appreciate it:]

[@InteractiveBiology]

@Matt18a That's what we do at Interactive Biology - Save Lives, lol. Hey, glad to know that you are getting value from it. Make sure to subscribe and stay tuned :)

[@InteractiveBiology]

@UniGirl9008 Unfortunately, Leslie has a lot of things to do at the moment, getting busy with the site, his work, and personal life. He's not had the time lately to check posts and get back to them. Please do stay tuned though as he'll be uploading more videos soon that may clarify your question. Thank you!

[@InteractiveBiology]

@adeelfromny Glad you find it helpful. Many more coming, so stay tuned :)

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You are a FANTASTIC teacher.

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[@James-jl6rx]

Clear explanation of what I was confused about! Thank you so much! :D

[@nerdyneeds6637]

When will we operate Na+- K+ pump?? Ideally it should happen in the state of repolarization ..but as you said in the wave of repolarization, K+ gated channels remained open which set up the ideal polarity .

[@InteractiveBiology]

Actually, the Na/K pumps are always going. However, depending on the state of the axon, it gets "overshadowed" by what's happening. Even though the Na/K pump is working during depolarization, there are so many Na+ ions coming in due to the V-gated Na+ channels being open that the pumps aren't really having an effect on the membrane potential. And they are working during repolarization, but are being overpowered by the K+ channels. Hopefully, that makes sense.

[@jimmyt1222]

Awesome video. Thanks so much for doing this. It would have taken me hours of reading from a textbook to reach this level of understanding. Thank you, thank you, thank you.

[@rmaissa4045]

thank you so much ... i study in french but because i didn't understand i try your video and it was so helpful .. thank you

[@dibyansukumarpalei8780]

Thanks a lot very helpful after a few days i have my 1st prof mbbs exam

[@SaddieMusic]

Thank you so much! I wouldnt change anything in this vid! Keep up the great work!

[@InteractiveBiology]

@Djalitana No prob. Glad you found it.

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@skinnimelon You're welcome. Stay tuned for more!

[@onlywei1487]

Thank you so much for helping us crush many difficulties

[@27capricia]

you are great. thanks for putting it in a way that i could get the concepts finally.

[@redmanhurricanes]

A black guy teaching Bio I love this brotha! Good video, island vibes lol.

[@laurelfree18]

Thank you, Thank you, Thank you. So easily explained. Life saver.

[@sollehinidris3142]

Hi Leslie, how about Functional Refractory Period?

[@mynameistaken96]

This helped me a lot, thank you!

[@doctor.angela]

Thank you so much. It's better than my books' explaination.

[@johnguillen68]

Thank you for your videos. As I read these chapters its kind of hard to understand what's going on without some kind of picture/video example. But watching your videos and then reading makes more sense.

[@zahraahmood4040]

The graph looks off. Where it says refractory period, it's suppose to say hyper-polarization. The reason main reason why hyper-polarization happens is because the voltage gated potassium ion channels take a long time to close (and open) which means more potassium is able to flow out of the cell therefore, causing our neuron to become hyperpolarized before it can return to resting membrane potential.

[@JesusMartinez-zu3xl]

Thank you!!!! I understood what the periods were but needed a visual aid!!. Thank u!!

[@InteractiveBiology]

@skinnimelon Thank you for watching the video. Unfortunately, Leslie is busy at the moment working a lot on improving the site. He is unavailable to answer any more questions. In the meantime, please go to our site directly for more Biology videos. New episodes will be uploaded very soon!

[@lindaandjeffsampson]

Wow! Great teaching, wish you were my teacher @ school. My teacher goes too fast.

[@berkayekiz9186]

Thanks alot sir, you've explained it quite simply :)

[@inass9713]

Thank you so much. You really saved me 😢❤️

[@AlexanderGuckenberger]

Thank you sir! This was very helpful, in my opinion! Bless you and thank you sir! :)

[@evii1545]

Thank you so much! I am taking this in class and you were incredibly helpful!

[@InteractiveBiology]

@thamer7A7 You're welcome! Stay tuned for new Biology videos coming very soon!

[@InteractiveBiology]

@LaSuraya1 Thanks Laura. Glad you like it :D

[@fireandice5969]

@UniGirl9008 Refractory period = Repolarization. Hyperpolarization are the K+ ions going further down towards the -90mV range before the pump kicks in to return the Na+ and K+ ions to their resting membrane potential.

[@2Aboody]

thank u for help me to understanding what the different between ARP and RRP

[@LSI_MGA]

By "resetting" you mean that the sodium voltage gated ion channels are no longer inactive, but are now deactivated, correct?

[@GlendaPimentelVergeldedios]

Thank YOU, Leslie! God Bless YOU!

[@7amood3abood77]

best video so far

[@shrutipathak2096]

Thank you sir From India🇮🇳🙏

[@shamamalihashim6159]

YOU ARE A LIFE SAVER. THANK YOU!

[@NightWanderer01]

Yes, Na+/ K+ ATPase restores these ion concentrations back to its resting levels.

[@InteractiveBiology]

@goozbye You're very welcome :) Please stay tuned. We have more Biology videos coming to the website soon!

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@TheRobbert1992 You are very much welcome :)

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@r3dfreak You're welcome!

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[@charlenem3371]

Thank you so much,I now understand.Keep up the good work!

[@malakali537]

we take in our physio coarse that the ARP is from the beginning of action potential to the point that soduim channels get close and this point is at resting before beggining of hyperpolarization part

[@ksufler]

Hello, first of all for the great and informative video, I think I'm getting it except one thing. I'm having a hard time understanding the RRP. You said that with only a few Na channels closed it takes a much more stronger stimulus to cause the deporarization again.. but logically it should be easier to open the lesser number of channels, than to open them all when they are all closed in the initial state.. I don't understand :c

[@HxAlabdulla]

dear, as I know you must open all the channels to get the right amount of stimulation in order to get a response..it should be the same amount as the previous stimulation... hope I'm right, this what I understand from the lecture

[@BabyBobRossJalapeno]

ksufler, an older example of relative refractory period is this: envision the flushing of a toilet bowl. upon first flush, the response is very strong, full flush occurs no problem (full depolarization, action potential). In the middle of this flush, you can push your toilet handle again and you will get no response from the toilet (absolute refractory period). but if you wait just past the midpoint of the first flush, you can actually push the handle again, but much harder to get it to start the flush process all over again (relative refractory). thus, relative refractory period is that state when you've already flushed the toilet, and need to exert greater force to flush again before the first flush has finished (returned to resting state). I hope this helps you understand the concepts and why a larger than greater force/stimulus is required to generate another action potential.

[@HxAlabdulla]

exactly thanks for relating this example to real life .. yeah I got it !! good luck to everyone :)

[@mohammadsammie4712]

HamdaSaeed 11s3 It might also be because the K+ efflux making the depolarization Harder and with a Portion of Na+ gates Inactivated there must be a stronger stimulus.

[@yashsaxena1217]

@UniGirl9008 Nah, hyperpolarization is a phase not a phase. When the mV drops below -70mV its called hyperploarization, and when it goes back up to -70mV its called polarization. Refractory period is the time it takes for a Na+ channel to open again. This makes sure the action potential moves in one direction.

[@hmzas3062]

This video helped me a lot. Thank you very much.

[@InteractiveBiology]

@ediniz101 Those questions are answered in Episodes 9 - 11 and 14. Check out those videos. They should help!

[@fehmeedaayoub6559]

I am not able to understand the tranfer of action potential across axon?? How myelinated nerve fibers are fast conductors and non myelinated are slow conductors.

[@colacasados]

Hello, and THANK YOU for your videos!!! They truly simplify information. Would you happen to have videos on ALL of the characteristics of Action Potential (including "nondecremental" & "irreversible")?

[@JBitzz]

Hey I heard ur interview on the Smart Passive Income podcast!! Now I'm studying for my neurophysiology midterm and I coincidentally stumbled to your videos haha. Th

[@Bindasjhakyass]

What is action potential duration? What is the difference between APD and ERP?

[@wahid001]

Interactive Biology The Voltage Gated Na+ Channels open after the threshold potential is reached. So if the membrane potential is lower than -55 mV, all Voltage Gated Na+ channels should be closed. The "all or none" response to reach the threshold potential is due to the summation ( Temporal or spatial) of action potentials. which you have already covered in " 019 What is Summation (2 Types)".

[@ashlu5477]

Thank you, this was so clear and easy to understand!

[@Larethq]

Thanks for the video. It really helped alot in understanding the process

[@Djalitana]

Oh I found it. please disregard my request about making a vid about refractory period. now I understand, the sodium chanel doesn't close like bang. it closes gradually right? and this causes that the second stimulus needs to be stronger than the first one to produce an action potential?! thanks for this clip

[@wahid001]

Interactive Biology Hey Leslie. Got a quick question. So as the neuron is repolarizing, a Relative RP is possible as long as as the repolarization period is between threshold (-55mv) and the resting potential (-70mv), including hyperpolarization (undershoot)?

[@sarahcarlson7916]

I was watching numerous videos from other sources and it was explained that the relative refractory period is from -70 to -70 during the refractory period. during the initial refractory (peak), sodium gated channels are locked and unable to open until -70, then they could restart an action potential with greater stimulus at or after -70 since the potassium is still open and does not close until -90/ hyper repolarization can you explain a little further as to why the refractory period starts at the initial decent? thank you

[@ayatomar9533]

Thank you so much Mr. Samuel

[@InteractiveBiology]

You're very much welcome, Ayat.

[@4thlineforlife]

guys quick question. after a stimulus when sodium ions rush into the cell and potassium rushes out are these molecules actively transported back to where they were in first place or what?

[@milagroswalker3806]

I finally understand this, thanks a lot.

[@e.b5911]

I am a little confused. The sodium voltage gated ion channels are inactive while the membrane is repolorizing. Why would that be relative refractory period and not absolute since the sodium voltage gated channel is still open (inactive) please? Thank you for your time and help.

[@InteractiveBiology]

Great question, Enerjola. Once we're in the repolarization phase, the v-gated sodium channels are starting to reset. It doesn't happen all at once. As you can imagine, if you're closer to the beginning of repolarization, only a few channels have reset. In the middle, more have reset. And by the end, ALL have reset. As they start resetting, it makes it possible for you to re-stimulate them to open. At that point, it's possible to trigger another action potential, but it would take a bigger stimulus to make that happen. For that reason, it's in the relative refractory period. Because while it's harder to trigger another action potential, it's definitely possible. Hope that helps.

[@e.b5911]

@@InteractiveBiology yes it makes sense. For the v-gated sodium channels that have just started to reset would be able to elicit another response, namely generate another action potential while during depolirazation is impossible. Thank you very much Leslie!

[@InteractiveBiology]

You're very much welcome, Enerjola.

[@Marieblue70]

Hi, thanks for the video!! I have a question: What happen to K+ channels at resting potential phase and during depolarisation? do they close during depolarisation but stay open at resting potential?

[@InteractiveBiology]

Which K+ channels are you referring to? V-gated or passive/leaky? If you're talking about V-gated, they are closed during those two phases. If you're referring to passive/leaky, they are always open, but during the action potential, their effect is negligible.

[@MsMoti93]

I totally Understood the concept xD Thank u sooooo muchhhhhhhh :D

[@InteractiveBiology]

@BreatheinStandstill LOL, it's kinda hard to understand gibberish ;) Glad you found value in the videos!

[@carolinespec]

Great video! Thanks so much!! You made it really easy to understand!

[@HildaSalama]

Does that mean that depolorization= absolute? I mean during depolorization, there is no way to start a new action potential...am i right?

[@drzainabtahir3554]

Thanks for explaining it so well.

[@ediniz101]

hi i love thevideos but i have a couple of questions umm firstly what causes the ion gates to open or close or be inactive? and why do the Na+ and K+ gates open at different times? thank you

[@MissAnnieDreamer]

You're amazing, thank you for the great vids! So helpful~

[@aloovertheworld4948]

Very good job explaining!!

[@InteractiveBiology]

Why thank you

[@nadinesp6141]

Samuel thanks for this video finally understood it!!!

[@InteractiveBiology]

You are very much welcome. That's why we create these videos. Glad to hear it helped. Make sure to share it with others who might also be struggling to understand it.