Action potentials in pacemaker cells | Circulatory system physiology | NCLEX-RN | Khan Academy

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Find out how the pacemaker cells use the movement of sodium, calcium, and potassium to get your heart beating! Rishi is a pediatric infectious disease physician and works at Khan Academy. Created by Rishi Desai.
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30 сен 2024

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Комментарии : 274

@khanacademymedicine 12 лет назад

I'm glad that you find the videos helpful! There are many more to come...

@sajjadmahmud3944 4 года назад

Absolutely brilliant. I have subscribed!

@005adityaanurag2 3 года назад

Please Overdrive suppression explain

@life42theuniverse 2 года назад

At what point does the sodium and calcium leave and at what point does the potassium enter? This example model would lead to a swelling of the cells with Na and Ca ions and the cell would be depleted of K within a few cycles...

@taniavelho511 Год назад

This is a very simplified version for non med people

@bbmtge 4 месяца назад

@@life42theuniverseThis is introductory. Read further and do some research.

@khanacademymedicine 12 лет назад

Potassium reenters the cells by the Na/K pump which is ALWAYS working to keep the potassium levels nice and high in the cells.

@carissawilkins3881 9 лет назад

These videos are so wonderful as a study aid for medical school! I can always come back to these to get down to the most basic concepts and extrapolate them to things such as anti-arrhythmic pharmacology. THANK YOU SO MUCH!

@madhuriaher7604 7 лет назад

cbcCarissa Wilkins

@ld1667 6 лет назад

I'm doing exactly the same lmao

@ayushigupta7632 3 года назад

Doing it right now

@MrUrbanExp 10 лет назад

I like this guy that helps Khan. His voice, straight forward, nice. easy to learn

@bhellar123 10 лет назад

0 stage (action potential) is because of Ca+ coming in(,not bc Na+ coming In as in cardiac myocyte) stage 1 and2 is not present in pacemaker cell because pacemaker do not have platue stage 3 is repolarization because K+ out leaving -ve inside stage 4 is activation of If Na+channel (because of repolarization by K+ out ward) now this Na+ wil depolarize to threshold (not action potential) to open Ca+ channel these Ca+ entry (or stage one again ) is action potentional (during whole phase ions are actively transporated to their orignal concentratioout and inside by Na K atpase pump and contratranprrt

@alimajed8843 9 лет назад

first of all, what cause the action potential is ( sodium and calcium ) , first there is ( slow sodium channels ) that make the potential reaches " threshold" and after that a channels call ( sodium-calcium channels ) activated , thus causing action potential ( both the sodium and calcium ) ( source ; Guyton, Textbook of physiology chapter 10, 117)

@GabrelHenson 3 года назад

i studied this for 6 years and still can't understand this shit

@gulayyalcin325 9 лет назад

So, there is a difference between action potentials in pacemaker cells and action potentials in cardiac myocytes?? Or was it just an example to use different ions coming into or going out the cells?

@medicamedico4335 7 лет назад

Gülay Yalcin there's a difference. Pacemaker cells are special modified cardiac myocytes.

@rahullovesthepayne8690 7 лет назад

Gülay Yalcin what I've read that is pacemaker cells unlike cardiac myocytes do not need any stimuli to generate Action potential.

@lrbolotin1227 7 лет назад

They are different. There´s another video of Khan academy about the pacemaker action potential, check it out.

@brittanymontero303 8 лет назад

This video, as well as the one on cardiac myocytes have been very helpful to me. However, in my Anatomy & Physiology course there are some pieces to the pacemaker cell action potential that were not in this video which I feel would be important to add. Terms: Funny Channels T-type channels L-type channels Early drift Late drift These pieces were shown in the video but not named.

@lorenzocosentino2755 8 лет назад

+Brittany Montero really helpful also for me

@SCPVIDEOPRODUCTION 8 лет назад

I don't understand how this can work. If Na is flowing into the cell and then Ca flows into the cell and K flows out of the cell. All the electrolytes need to go back. K needs to get back in the cell, Na and Ca needs to move back out of the cell. The switching back of all the electrolytes is not talked about. How can we just start over if all the electrolytes are not in the correct area?

@jakublubojacky8242 8 лет назад

excatly... it explains only one cycle

@sakshijoshi7169 8 лет назад

Basically there are two kinds of K+ channels: rapid delayed rectifiers (IKr) and inwardly rectifying (IK1). IKr is the primary channel, so there's a net outward, positive current (making the inside of the cell more negative), and this is repolarization. IKr closes when the membrane potential is about -85 to -90 mV. BUT the IK1 keeps open throughout phase 4 (allowing K+ to return inside). The Na/Ca exchanger and Na/K pump also help to restore ion concentrations. So like, the Na/K pump is an ATPase that pumps both ions against their concentration gradient, which means it'll pump Na+ out & K+ in, thus returning everything to how it was!

@hilaltuncer6149 7 лет назад

what about Na?

@AlejandroRamirez-uv9ir 7 лет назад

The Na+ and K+ ions are "replaced" by Na/K ATP-ase which pumps 2 K+ ions into the cell for every 3 Na+ ions out of the cell and re-establishes these ion gradients. The Ca+ ions are also pumped out of the cell in a similar fashion. Bottom line- there are many ion channels and other membrane proteins at work. This is just a simplification of how "action potentials" work in the nodal cells.

@medschoolgear5320 6 лет назад

I studied biology in undergrad; I did well on the MCAT; I am a second year in med school.... and this was the best explanation of how action potentials work I've ever seen. I can't even begin to thank KhanA for their work.

@1traviscarr 11 лет назад

Can someone explain to me why during phase 3, if K is leaving the cell how does the cell's mV become more negative. If K has a - charge than in my mind the cell would increase it's + charge. Thank you for anyone's help. Thank you for the video as well!

@ahmedfarniz3966 2 года назад

because K+ is effluxing

@nihvl 8 лет назад

There is no word about" funny current " ?!

@wellali2574 8 лет назад

the funny current is the inward Na current via Na-leak channel that is done by HNC channels

@christopherfrigo315 4 года назад

@@wellali2574 Inward K leak as well, right?

@sandamaaljayasekara 11 лет назад

The action potentials in the SA and AV nodes are largely due to Ca++, with no contribution by Na+ influx (Ganong's Review of Medical Physiology, Twenty-Third Edition Chapter 30 -Origin of the Heartbeat & the Electrical Activity of the Heart. Sub topic- Pacemaker potentials.) Please explain this

@bbmtge 4 месяца назад

Sodium ions cause the pacemaker current in cardiac cells, which causes the membrane potential to change from -60 mV to reach the threshold potential of -40 mV. This slow influx of sodium ions through the hyperpolarization-activated cyclic nucleotide-gated channel (HCN channel) generates the pacemaker potential. The slope of phase four determines heart rate and is different for pacemaker cells in different regions. For example, SA node pacemaker cells depolarize at a rate of 60 to 100 per minute, while the AV node at 40 to 60 per minute.

@huh1448 10 лет назад

These really are the most educational videos you're going to find on youtube, great work!

@angelgabrielramirez9196 2 года назад

K. Kl l

@Asdw_asdw_12395 8 лет назад

I love your voice and the way you talk. I know this is crazy but will you marry me?

@axa.n3319 7 лет назад

haha

@BaldMurse 4 года назад

Hye Sun Lee yes

@bokhariahmed5490 9 дней назад

The beauty of emotional insight. You were able to evaluate a man by his voice. You are amazing.

@TheEgyGeek 9 лет назад

15:36 lol

@hydrocarbon2195 6 лет назад

lmao

@wingchingchoi7181 4 года назад

okay im not the only one noticing this lol

@GozieZilla 11 лет назад

the 4, 0, 3 numbering system is used because in 'non pacemakercells' the 0 represents Depolarisation and the the 3 represents repolarisation and those two numbers represent the same events in 'pacemaker cells'. Thats why they chose those specific numbers.

@MsTattygrass 10 лет назад

Thank you so much for the videos. You make complex materials so much easier to understand and explain things which are often missing from textbooks. I also love your voice.

@Kamishai 12 лет назад

If only I had lectures like this! Easy to follow. Thank you for posting!

@fitnesschannel9070 2 года назад

Of course you don't. I don't either. It's not necessarily that your lecturers are bad or unskilled - it's just that khan academy team is one of a damn kind and it is an absolute blessing for us to have access to them

@eMJayZH 10 лет назад

Good job!!! I wish our teachers would explain things like you. Than I would start going to their lectures...

@ericanewell9141 6 лет назад

Thank you!!!!! I LOVE khan academy videos! My sister-in-law introduced them to me recently because I was getting rusty on a few things. They're so easy to understand in comparison to how I learned info in nursing school. Education is a big part of a nurse's career. With these videos, I feel I can educate my patients better.

@johnarmstrong8101 10 лет назад

can you make a video explaining (If) channels or funny current channels

@arazmed 10 лет назад

amazing video. thank you very much

@TheMattJames 2 года назад

so what we just have an endless influx of Na entering the cell.... i don't get it, how does this Na eventually get removed

@mayaouwehand3695 9 лет назад

Thank you so much, for this video! It helped me a lot to understand cardiac electrophysiology !

@isabellapedregon3719 2 года назад

I have never been able to grasp the concept of action potentials within the cardiac muscle cell no matter which professor for A&P 1 or 2 trying to explain it but this video with the diagrams and everything have single handedly saved my life lol

@alamgirkabir6483 6 лет назад

thanks a lot for these videos as I learned about how , the human heart works.....thnks

@slayer41126 11 лет назад

What about the Bachmann's bundle and the internodal tracks? are they made up of pacemaker cells? If so, does that mean that those cells could fire spontaneous action potentials if the SA node, AV node and purkinje systems are not working? if they're not made out of pacemaker cells, then are they just made out of normal cardiac muscle cells?

@milantenbosch 2 года назад

Kind of like a redstone clock

@paulson2008 7 лет назад

Those dislikes are from teachers 👨‍🏫 who can’t teach like you do 😂😂❤️🤘🏼

@lakshmishajahan8391 3 года назад

Wow. What a wonderful explanation! Thank you so much!

@mariamgujuram1524 3 года назад

I love these lecture or videos that you post thank you and easy to understand

@yifanwang3101 7 лет назад

what cause Na+ channel initially depolarize? and what makes calcium and potassium gate open or close? the different electrostatic gradient? never understand it!!! HELP!

@SumanDasgupta-m1l Год назад

Whatever you said explains the continuous generation of action potential well, but it leaves one question. And that shows the flaw of the model you used, perhaps you missed something important. The question is if things happen as you said that over the time the cell will be rich in Na+ , Ca++ ions and will have heavy deficiency of K+ ions, because they are continuously moving in or out of the cell. So the extracellular sodium , calcium concentration will become low at a point and intracellular potassium concentration will become also low, hindering this phenomenon to happen further. So during the cycle also sodium, calcium should be pumped out and potassium should be pumped in to restore the concentration gradient back to normal condition. Please include that part in your explanation.

@baburo101 12 лет назад

There's a reason why you joined the Khanacademy team; you fit right into Sal's "intuitive" (not to mention that you sound a bit like him) way of teaching. Thanks to all of you guys for broadening the library.

@red-baitingswine8816 Год назад

This guy is intelligent and very knowledgable (and interesting), but long on hand waving and short on complete, logical explanations.

@ludmilavins6984 8 лет назад

In the rising phase of cardiac autorithmic cells Na + permeability does not change . Rising phase is due to diminishing permeability to K+ ions. Na + influx is the cause of rising phase of action potential of cardiac contracting cells, and it's completely different mechanism altogether . Please review it and do not confuse viewers . And calling Na+ salt three times in a row is not cool either . Good luck :)

@Dr.Red_pirate 8 лет назад

+Ludmila Vins you're right, he messed up a bit in this video

@mehnaazali5471 6 лет назад

Do you even reply to any of the comments? We have doubts and you don't care...is this all to earn money from RU-vid or to spread knowledge?

@taniavelho511 Год назад

Bundle.of his is not purkinje fibers. Bundle of his devides in to two parts left and right branches and these branches divides in to smaller purkinje fibers. The action potential changes from cell to cell so the bundle of his is different than purkinje cels

@ramzeschavez 10 лет назад

what software is it your using (drawing) does anybody know??????

@GabrelHenson 3 года назад

it took me 6 years, but probably just fullscreen ms paint

@jessm3270 10 лет назад

@3:00, where are you getting the numbers from?

@Radar101music 7 лет назад

You missed to explain T-type calcium channels

@eiklinoh9402 7 лет назад

thank you ^^ I really needed this to understand :)

@janaenae1338 3 года назад

So my potassium channela are broken and i used to use methamphetamine Nd i developed super body odor could you explain that to me

@klausnewman8125 4 года назад

I thought it was 90 - 100 beats per minute and normal heart beat rate was in part due to sympathetic and parasympathetic activity?

@janaenae1338 3 года назад

I got bullied to the point of complete isolation and it changed my life completely ... What the heck even happened

@eleopeste 8 лет назад

So clear thank you!

@rahush7245 11 лет назад

Phase-0: Slow ca channnels open; calcium influx. "Resting K channels close due to this depolarization. Phase 3: Repolarization due to calcium channels closing and k channels opening which allows unopposed k efflux. Phase 4: "Diastolic-Depolarization (automaticity). why? Slow closure of K channels and sodium slowly leaking into the cell (SLOW) (imp);catecholoamine or b1 agonists act here by increasing "SODIUM- INFLUX) leading the cell become more positive until it reaches a threshold.

@PirateMate309 11 лет назад

The entirety of the action potential (phase 0) is due to the Ca2+ ions. Na+ ions must influx in order for the membrane to reach the threshold, which then leads to the action potential. Just a misunderstanding of wording. :)

@anjacumic7034 8 лет назад

His voice is identical to Jacson Avery's from Greys😍

@teejay7171 8 лет назад

i thought i was the only one who noticed that 😛

@saraireg8373 8 лет назад

Anja Cumic haha seriously! Lol

@annpank 11 лет назад

the colors are so pretty

@semaalex1751 11 лет назад

some of the text book says that the Na channel closes after the rapid depolarization, and the beginning of the re-polarization. What's your opinion on it?

@lyricson4ya 2 года назад

I loved loved this...this is absolutely appropriate and more

@kevinking7414 10 лет назад

Thanks. What playlist is this part of?

@kowlahaliyani9880 2 года назад

Thank you 🙏🏻 thank you thank you sooooo much you saved me ,,, I was lost

@peternader603 7 лет назад

is the automaticity character due to inflow of Na as you said in the video or slow inward Ca currents ?

@mnopyzstrife188 7 лет назад

en.wikipedia.org/wiki/Cardiac_action_potential#Phase_4 I had the same question. Apparently, it's due to both. (Along with a decrease of Potassium exiting). "This pacemaker potential is predominantly due to increased inward current of sodium (Na+) through voltage-dependent channels, but also an increased inward calcium current and a slowly decreasing potassium outward current." I hope it helps :)

@kie1818 11 лет назад

The sodium-potassium pump is still constantly going, pumping those sodium ions out of the cell to maintain the low concentrations :)

@MA-hb1jo 8 лет назад

What made the sodium gate open in the first place ?

@peterlolpeterson 8 лет назад

+Meshari AA They are opened when the Voltage in the Cell gets below -50mV

@RedTheSaviour01 8 лет назад

+Meshari AA its naturally leaky

@anonemi5630 4 года назад

But is an actual potencial only produced in depolarization or is it also produced in repolarization ?

@thewwefan57 5 лет назад

God bless the internet, thank you

@tessasommeling1956 5 лет назад

So confused. If potassium goes out of the cell, the cell shouldn't become more negative right? Because potassium is negative and LEAVES the cell. According to my book, there is an 'influx of potassium so membrane potential returns to resting level'. However, in this video potassium leaves the cell...

@MrMidway77 5 лет назад

how is potassium negative lmao

@DhiliphanRaja 7 лет назад

since k+ ion is the positive ion why it keeps the cell in -92mv

@asterefferescent573 4 года назад

Because it keeps leaving the cell. But, I missed the part when it comes back in. It can’t just forever leave the cell, right? Can anyone explain?

@YEEAAGREEN 10 лет назад

Great video, one thing though. You refer to the sodium going into the cell as "salt". Sodium should not be called salt because "salt" is sodium and chloride together. You can throw people off with your wording.

@TheRedStarman 5 лет назад

If you're watching this video, then you can see he writes Na+ when he says salt. No one is going to get thrown off by this.

@bbmtge 4 месяца назад

Stop looking for an excuse to correct someone who is clearly superior to you with respect to this subject...and likely a lot more.

@1123ellipsis 11 лет назад

I_funny is the slow influx of Na+ which he draws in white at the beginning, but does not name.

@husseintouma5313 2 года назад

But how the k influxes into the cell again? Do we use pump

@thesidemen1236 3 года назад

are there any relative or absolute refractory periods in SA node?

@VickiBee 10 лет назад

This is what I do for a living. ECG Technician and Paramedic. I thought you were going to be talking about pacemakers that people have implanted in them when their hearts fail to work right.

@leydisguerra5759 5 лет назад

Are these pacemakers cells autorhythmic fibers?

@MarmiteFerret 6 лет назад

I commented on another video as well so apologies if there is an answer there. I am a bit confused about the voltage-gated channels. So at -40mV the Ca2+ channels open, and presumably remain open, until +10mV is achieved, at which point they shut and the cell tends towards a more negative charge again. What stops Ca2+ channels opening again the moment the cell's charge drops slightly below +10mV i.e. why do they stay shut until the next upwards rise to -40mV. Indeed, why do they not open again as the charge travels back down past -40mV? EDIT: I assume this relates chemically to the absolute refractory period but it is unclear to me what prevents the voltage gated channels from reopening.

@MeaHeaR Год назад

Ná+ ISUNT SALT, it is a ION Salt is Neutrâl NaCl

@nabilatabassum4543 11 месяцев назад

I still dont get why pacemaker potential is needed

@Mondrulho 6 лет назад

Doesn't look very accurate. In the pacemaker cell we don't have Na channels. Only K channels, Ca Chanels and "funny" Chanels fo the "if current"

@mewael1980 9 лет назад

So, it has been said, Na+ goes in first till it gets to the threshold potential and then ca++ picks up and spikes the action potential; then after, K+ goes out more and it gives us that graph. My question is, how does the ions be replaced in the ECF and ICF afterwards???

@funzoola2005 6 лет назад

what about the plateau where the ca2+ and the k+ causes a stall before repolarization? can you explain what's going on during that section? it would be most appreciated and help things click a little more for me. please and thanks :-)

@Popcorn9258 10 лет назад

Arent those natrium channels you are talking about actually different calcium channels? (L type calcium channels) Thanks for answer and also thanks for awesome video :)

@yazmindeebayram 12 лет назад

Loving this series of videos!!!!!!!

@briana6547 Год назад

THANK YOU for explaining all the math!!! Most teachers don’t even care about it or to explain it, now the numbers make more sense now and it’s easier to grasp the concept

@natashavityaak 8 лет назад

Why is it when K+ is present the voltage is negative? Wouldn't the overall voltage be positive still when another positive ion is present? This is how the heart repolarizes when kicking out K+ to go back to negative. Care to explain please?

@AfuaA839 7 лет назад

pacemaker cells have a slower upstroke compared to non pacemaker cells (cardiomyocytes) because there is no influx of Na+, only Ca++

@panchozeta2821 3 года назад

In what phase does the K+ go back into the cell? 4?

@ghazzwaq9248 6 лет назад

the world need more heroes..... who have gifts in explaning. the XPLAN-MAN!!!!

@lrbolotin1227 7 лет назад

I am confused, he says that this AP is slower but I found that pacemaker lasts 100 msec while myocardial lasts 200 msec

@taratareen7776 3 года назад

If potassium is a positive ion, then why would the membrane potential be negative if it was the only ion moving and out the cell? Thank you so much for this helpful video! ❤️

@user-pr9np4cj9l 7 лет назад

How does the calcium ions and potassium ions leave the cell...? Through open channels...?

@bokachagol 6 лет назад

Thank you sir for sharing such a great video..but sir I have a question..why are the limits +10mV and -60mV?

@MR-du7uj 3 года назад

Amazing! 👏

@akhilaryappatt 3 года назад

actually, don't we think in voltage too?

@josievv336 7 лет назад

Amazing video! But just to make sure, the Na+ voltage-gated channels are always open no matter what the other channels are doing, right?

@missreddish 10 лет назад

You vids are sooo helpful. Im studying at university and think the vids are a reallu gd was to get to grasps withbthe basics. Thank you

@tiffa8213 7 лет назад

You never got back to why you started at -60 mV... can someone please explain?

@khdr4165 7 лет назад

why we started with minus 60 ?!! wheras in cardiac muscle we started with about minus 90 ?

@rocc6596 7 лет назад

so when the ca++ and the Na ions goes inside the cells and the K out, do they stay in there until the next action potential reversing the ions back to where it originally were located with Na and Ca++ out outside the membrane and the K in?

@yes7855 3 года назад

YOU ARE AMAZING I THINK IM IN LOVE WITH YOU

@محمدحسينالصيدلي 8 лет назад

i just wanna say how great you are my god!! So wondrous. God created for us these cells and with high accuracy !! nobody can create these cells just a god