Action Potential in Neurons, Animation.

(USMLE topics) What is Action Potential? How is it Generated in Neuron? Clear and Concise Explanation of Phases.
Purchase a license to download a non-watermarked copy of this video on AlilaMedicalMedia(dot)com
©Alila Medical Media. All rights reserved.
Cells are polarized, meaning there is an electrical voltage across the cell membrane. In a resting neuron, the typical voltage, known as the RESTING membrane potential, is about -70mV (millivolts). The negative value means the cell is more negative on the INSIDE. At this resting state, there are concentration gradients of sodium and potassium across the cell membrane: more sodium OUTSIDE the cell and more potassium INSIDE the cell. These gradients are maintained by the sodium-potassium pump which constantly brings potassium IN and pumps sodium OUT of the cell.
A neuron is typically stimulated at dendrites and the signals spread through the soma. Excitatory signals at dendrites open LIGAND-gated sodium channels and allow sodium to flow into the cell. This neutralizes some of the negative charge inside the cell and makes the membrane voltage LESS negative. This is known as depolarization as the cell membrane becomes LESS polarized. The influx of sodium diffuses inside the neuron and produces a current that travels toward the axon hillock. If the summation of all input signals is excitatory and is strong enough when it reaches the axon hillock, an action potential is generated and travels down the axon to the nerve terminal. The axon hillock is also known as the cell’s “trigger zone” as this is where action potentials usually start. This is because action potentials are produced by VOLTAGE-gated ion channels that are most concentrated at the axon hillock.
Voltage-gated ion channels are passageways for ions in and out of the cell, and as their names suggest, are regulated by membrane voltage. They open at some values of the membrane potential and close at others.
For an action potential to be generated, the signal must be strong enough to bring the membrane voltage to a critical value called the THRESHOLD, typically about -55mV. This is the minimum required to open voltage-gated ion channels. At threshold, sodium channels open quickly. Potassium channels also open but do so more slowly. The initial effect is therefore due to sodium influx. As sodium ions rush into the cell, the inside of the cell becomes more positive and this further depolarizes the cell membrane. The increasing voltage in turn causes even more sodium channels to open. This positive feedback continues until all the sodium channels are open and corresponds to the rising phase of the action potential. Note that the polarity across the cell membrane is now reversed.
As the action potential nears its peak, sodium channels begin to close. By this time, the slow potassium channels are fully open. Potassium ions rush out of the cell and the voltage quickly returns to its original resting value. This corresponds to the falling phase of the action potential. Note that sodium and potassium have now switched places across the membrane.
As the potassium gates are also slow to close, potassium continues to leave the cell a little longer resulting in a negative overshoot called hyper-polarization. The resting membrane potential is then slowly restored thanks to diffusion and the sodium-potassium pump.
During and shortly after an action potential is generated, it is impossible or very difficult to stimulate that part of the membrane to fire again. This is known as the REFRACTORY period. The refractory period is divided into absolute refractory and relative refractory. The absolute refractory period lasts from the start of an action potential to the point the voltage first returns to the resting membrane value. During this time, the sodium channels are open and subsequently INACTIVATED while closing and thus unable to respond to any new stimulation. The relative refractory period lasts until the end of hyper-polarization. During this time, some of the potassium channels are still open, making it difficult for the membrane to depolarize, and a much stronger signal is required to induce a new response.
During an action potential, the sodium influx at a point on the axon spreads along the axon, depolarizing the adjacent patch of the membrane, generating a similar action potential in it. The sodium currents diffuse in both directions on the axon, but the refractory properties of ion channels ensure that action potential propagates ONLY in ONE direction. This is because ONLY the unfired patch of the axon can respond with an action potential; the part that has just fired is unresponsive until the action potential is safely out of range.

[@Alilamedicalmedia]

Love this video? Check out our new A&P course, with more than 80 videos like this (no watermark, no ads), over 40 PDFs and hundreds of images: For student: www.alilaacademy.com/courses/anatomy-and-physiology-for-students For teachers: www.alilaacademy.com/courses/anatomy-and-physiology-for-teachers NEW: Now you can also get access to our courses with our KZbin channel membership (Academy Access levels)

[@hidaayattv]

Always remember the word 'INK', I : Inside the Cell. N : Negative Charge. K : Potassium. ❤️

[@SantoshPatil-ht1cd]

👍👍

[@lara.lara0]

Ty

[@neha17498]

Thank you for this so so helpful and easy to remember 🧡

[@donaldendratrumpodi6225]

Ok ola hu uber

[@blueblood-_-]

Yes bish

[@riddhipatel4747]

Literally saved our lives! Explained in minutes what was confusing us for hours. Thank you so much and keep up the great work!

[@N12Gautam]

Riddhi Patel u mean mentally

[@anyasin9142]

I agree

[@rahulxx2619]

😬

[@halaa9319]

facts

[@Kartik-xw7yt]

Actually..!

[@Alilamedicalmedia]

Thank you for watching! Follow us on Twitter twitter.com/AlilaMedical for instant notification of our new videos!

[@mellisaalvarez4859]

I just learned a whole week of lecture in 6 minutes. Thank you!

[@Sanvideshmukh6118]

Yup....Mee 2

[@izarscharf7845]

More like 5 mins of lecture ...

[@brittanyjin4723]

One of the best explanations I could find. I was really confused about the pumps and refractory periods but now I understand what my text book is trying to explain.

[@user-cn8fi4tv8j]

😂

[@Mouthymensch]

THANK YOU THANK YOU THANK YOU!!!!! When my professor explained this in class I was so confused but this helped me actually understand it!

[@thelabadabada]

This is the most accurate explanation of Action Potential in Neurons .... compared to the other videoeS! thank you!

[@CristianDiPuorto_glockshock]

As an engineer I couldn't find a satisfactory edplanation on depolarization; thanks to this video It now makes much more sense. Thank you and keep up the good work!

[@josephdesensi1919]

Absolutely relieving! Great explanation that was clear and unlike every other explanation, not too many extremely complex words were used in one sentence which is the giving up point for most people. Thank you

[@skawah1995]

Most helpful video I have seen so far. Thank you!

[@ThanhKhoi1999]

I shed a real tear watching this video... 10/10 excellent job

[@mohammadrafiulhoque9183]

Great work! Cleared my concepts finally.

[@akhionline]

Very well explained with supportive visual animation. Simplified and brilliant. Had to subscribe :-)

[@haonhu7884]

Thank you so much. This is the best video that I have found so far for my class.

[@11Tyler]

I have a huge Anatomy final tomorrow and this video was just what I needed. Excellent job. Can't wait for your future videos.

[@und3rcut535]

why do you lean this in anatomy this is physıology

[@maricarmen8776]

Thank you, this video was tremendously helpful.

[@Far096]

Best video on KZbin regarding this topic

[@samruddhibansode8097]

The best animated explanation ever👍🙏...This short video made my work lighter

[@sydneyfloyd8940]

I wish I would have watched this video two days ago it would have saved me a lot of headache! AMAZING explanation! Thank you so much :D!!!

[@analien7458]

This is SO WELL EXPLAINED thank uu

[@marella3]

Great explanation!! Thanks!

[@drabdirahmansaladibrahim4602]

One of the best animated mechanism I saw of AP Well done

[@Jossha7]

A video made years ago just saved me☺️☺️. Alila the best

[@Glow87able]

You've officially earned a subscriber! Thank you soo much for a great video!

[@Alilamedicalmedia]

Thanks for watching!

[@KamLisa4630]

This is so clear!Thank you

[@rishankuparrangslang3802]

THANK YOU SO MUCH! i wish they'd just use these animations for lectures as well, would make our lives so much easier.

[@Alilamedicalmedia]

Thank you for your comment. In fact many universities and colleges use our videos for lectures and on their online learning portal. You can certainly suggest to your teachers :)

[@hiraafzal6208]

@@Alilamedicalmedia yes! Our physiology teacher use and recommend us too to watch your videos

[@MrsHarryPotterFan97]

Thanks so much! Greatest video ever! Wonderful explanation!!!

[@AmatistaCristales6]

I finally understand now. Thank you for this.

[@michellekristen7540]

The most accurate video I've seen. I wish it talked about sodium's inactivation gate though.

[@Alilamedicalmedia]

Thank you, we will keep that in mind for future updates.

[@archanaraheja2231]

Michelle Kristen *Hmmm*

[@sz2886]

So comprehensive and fluid!! Thank you.

[@nopenope6909]

Ah yes the good ol' Axon ʰⁱˡˡᵒᶜᵏ

[@theambrosius105]

Lol

[@VEN0MXVI]

I was looking for this comment, thank you.. I can rest easy now.

[@monkeyaxe3351]

Lol

[@somethingnew8336]

🤣

[@mohammedomar8616]

This video is sent from heaven😂 Thank you for this amazing explanation

[@athermalik8128]

Thanx for posting this video.It helped me a lot

[@dulmin_]

Thanks a hell lot of times! This will save me tomorrow

[@annav95]

Helped me a lot! Thank you

[@annav95]

Helped me a lot! Thank you :)

[@user-gj9db7wj2y]

Clear all the concepts...thank you very much...🙏🙏🙏

[@Shenice27]

This was great, thank you!

[@samuelcaruso5128]

ShenLB I’m half cactus

[@rawankarim9490]

Thank you from the bottom of my heart

[@RakeshGupta-gk8hz]

Best explanation!! Thanks...

[@emilius_525]

This is sooo helpful. Thank you thank you

[@leilaniahkoi]

I have been struggling for weeks and in just a few minutes you have eased my understanding of this specific process. You have given me hope to pass my test. I 100% appreciate this awesome video. Thank you! Thank you ! Thank you!

[@Alilamedicalmedia]

Glad we could help :) Good luck with your test!

[@fellforfall9802]

Very clear, thank you!!!

[@yussyed]

So helpful !!great job !! God bless you 😊😊

[@lissiep1356]

its really good. Easily understandable. Thank you.

[@Alilamedicalmedia]

Thank you for watching!

[@vikash1423]

Wonderfully explained thank you

[@narendrazinzala8761]

The best learning channel

[@Kiips-academy]

It was phenomenal 👌

[@sidoradam5021]

This is what I call a good job!

[@nnj1461]

U guys are so helpful.☺ thank you 💪

[@banhichowdhury1019]

Excellent! Thank you so much for this Amazing Video!

[@naturelove3716]

You are right i like this video perfect understanding

[@sanabutt2599]

thanks a lot for this brief explanation

[@munazzasikandar9208]

Very well explained!! 👍👍👍

[@aortanyc510]

excellent !! Thank you so much!

[@SantoshPatil-ht1cd]

It's easy to understand due to animation..... thank you so much 👍👍👍

[@dimpideepika]

This taught me so much regarding conduction of action potential thnq u so much for sharing 🙏

[@publicinterest8111]

One of the best explaination i found .....

[@thekillerphython]

wow best video on KZbin till now 👍👍👍👍👍

[@noone-gj5xv]

It was so much helpful.... Easy to understand that.... Keep it up champion

[@7D7N7A7]

You are the BEST !! Thanks a lottt

[@gabriellobo3456]

You are a real legend like OMG. This literally taught me what i was struggling with. Thank you

[@Alilamedicalmedia]

Thanks :)

[@bookworm6920]

That is very useful thanks so much 👏🏻👏🏻

[@Melo-wy6ki]

After watching lots of videos about action potential really when I exhausted that time I decided to watch this last video really this video helps me lot and ur explanation and video just amazing thanks !!!!

[@anyasin9142]

Very well explained :)

[@budekins542]

Thumbs up for this animation.

[@sa.h9640]

amazing! thank you

[@ladingtonrahe8137]

Well explained.Thanks for sharing😍

[@renad.3k]

This lesson was one of the most difficult lessons in school. I did not know anything about it. After watching this video, I became able to solve all the questions on it, even those that are not in my approach. Thank you for this useful video. 🤍💫

[@shivompokhriyal4589]

this video was very good to watch

[@shireennazeer7510]

Thanks for sharing such a Great video dear..... I was very confused but this animation really help me to understand the concept... 👍💕

[@naflanwizard]

Thank you so much Very useful explain

[@mystryshadm]

thanks a lot for the explanation..:D

[@amangull4973]

Amazing talent you have

[@hkcamanda6150]

Thank you sooooooo much.you saved my life .please continue to makd videos like this.

[@AbdulHadi-nu1sw]

Best explanation ever one can get 👍👍👍

[@IkeUzoaruJr]

this is beautiful

[@kajalpandey5021]

It is really very very helpful. Thank you

[@mawienmajock4742]

The topic which took me two weeks to understand is now understanded in just a few minutes.

[@vineetapant9040]

It is very well explained.. Thanks for the video

[@riyaz262]

Thank you great work

[@esq8]

Thanks! My notes were confusing. Couldn't figure out what was happening with K and when it was leaving the cell. 2 hours of reading and struggle solved in 6 minutes. Sheesh! Thanks again!

[@Stefan-ij1qb]

This is amazing

[@severerevenge8575]

Good video, as usual

[@liyaseyoum6693]

Than you, it's really helpful!!

[@deepikathakur299]

Great explanation thank you so much..

[@indigorulz]

An hour intense class covered in 5min with good animation! Good job..

[@shanuvadera7529]

Its the best video with excellent explaination

[@iyaylim2989]

Excellent explanation, great work!

[@Alilamedicalmedia]

Many thanks!

[@shaimaboosary1413]

Great work.. Thank you..

[@gandhimathiselvaraj7950]

Excellent animation video

[@yasminehabtawfik1981]

best explanation ever !

[@mazharfatmasiddiqui1657]

Thank you it's very helpful for me

[@adnannarvel226]

Omgg..this helped meee i have been studying since 3 hrs...lovelyy..u deserve my subscription:)

[@studentlounge5102]

Helped a lot... thank you

[@bankewadmaroti5062]

nice explanation ....thank you so much.

[@arnabsarkar1076]

Thanks ,it helped me a lot...

[@sweetybaishya6397]

Best lecture ever

[@Thisispow]

Amazing!

[@akshitasharma4581]

Very well explained