In this episode, Leslie talks about how a pacemaker potential can cause a heart to beat automatically. Details about how it is generated is discussed in this video. Just how does this happen, our heart beating again and again?
Watch to learn more. Have fun and enjoy!
Transcript of Today’s Episode
Hello and welcome to another episode of Interactive-Biology TV where we’re making Biology fun. My name is Leslie Samuel and in this episode, Episode 45, I’m going to be talking about the pacemaker potential of the S.A. node and the A.V. node. We’re basically going to look at how this results in the heart beating automatically. So, let’s get right into it.
Let’s first talk about the S.A. node. The S.A. node stands for the sinoatrial node and you can see it in this figure over here, it is number one. That’s this cluster of cells. It is basically a specialized group of cardiac muscle cells that don’t contract which is kind of strange. They’re muscle cells and they don’t actually contract.
But, what’s special about these cells is that they are adapted to automatically generate impulses. So, it can automatically cause signals that can spread throughout the heart, causing the heart to beat. The S.A. node functions as the pacemaker of the heart. Yes, we have the A.V. node and some other stuff that we are going to talk about but, these generates signals faster than any of the others so, it sets the pace for the heartbeat.
As you can see, it is located in the right atrium. So, now let’s talk about the A.V. node.
The A.V. node is number two. So, it’s this cluster of cells here and it stands for the atrioventricular node. It is similar in function to the S.A. node in that it automatically generates impulses and it is located between the atria and the ventricles hence the name, atrioventricular node. Let’s go back to the S.A. node and see how this results in the pacemaker potential.
Before we look at that, I just want to point out that we have, in addition to the S.A. node and the A.V. node, we have some fibers that extend from the A.V. node and spread throughout the ventricle and those fibers are called Purkinje fibers. These are also very important in that they spread that signal throughout the rest of the ventricle. Let’s talk about the S.A node.
We said that that functions as a pacemaker. So, we are going to look at the pacemaker cells that we have in the S.A. node. What is special about these cells is that normally, there’s a significantly higher conductance for sodium than there is for potassium. Now, if you go back to Episode 006, I talk about Donnan equilibrium and driving force and I show how there’s normally a driving force for sodium to rush into the cell. I also show that potassium wants to leave the cell.
Because the cell is much more permeable to sodium, we’re going to have a situation where there’s much more sodium coming in than potassium leaving. Because we have more positives going in than leaving, what we’re going to get is a pacemaker potential where the cell normally depolarizes. Then, when it reaches the threshold, something interesting happens. Yes, we have the sodium rushing in and some potassium leaving but, now that we’ve reached the threshold, voltage-gated calcium channels open and calcium is going to rush into the cell.
So, we’re going to get this rapid depolarization. In other words, we’re going to get an action potential. At the peak, we’re going to get a different situation where, yes, we have sodium coming in and potassium leaving but, voltage-gated potassium channels are going to open so that the conductance for potassium increases significantly and potassium is going to rush out of the cell repolarizing the membrane.
At that point, we still have the sodium that’s coming in and the voltage-gated potassium channels close so, we have the initial situation where sodium is rushing into the cell, causing this depolarization then, the same thing happens. It reaches the threshold, voltage-gated calcium channels open depolarizing the cell membrane once again, causing that impulse. Voltage-gated potassium channels open causing potassium to rush out of the cell again.
This process continues over and over and over. What ends up happening is we have this automatic signal that’s generated constantly resulting in the contraction of the heart. This causes the heart to beat. It’s really that straightforward but, the main idea is that the cells in the S.A. node have a significantly higher conductance for sodium so it continuously depolarizes causing that impulse that causes the heart to beat.
That’s really all I want to talk about in this video. As usual, you can visit the website at Interactive-Biology.com for more Biology videos and other resources to help make Biology fun.
This is Leslie Samuel. That’s it for this video and I’ll see you on the next one.
in Vanders Human physiology,it is written that Calcium channel open only briefly and it is an important depolarizing boost to pacemaker potential.
nice video!(thumbs up)
That’s correct. When the pacemaker potential reaches threshold, the Calcium channels open briefly causing the depolarization. That’s what is illustrated in the video. Glad you like it.
All the best!
Leslie
thanks, you are superb in explaining all that 🙂
Thank you 🙂
@Azamspazam91 I almost can’t bare it! 😀
@tiarafazlin17 I LOVE saving lives with Biology 😀 – Stay tuned for MANY more, and make sure to share the site with EVERYONE you know who might benefit 😉
i got 87.5 on my first lecture exam , i used your information and i guess it works out really well…. you don’t need be a rocket scientist to understand this.:)
@madej1858 WOOHOOOOO, Congrats on your success. Nope, rocket scientist is unnecessary 🙂
That is so helpful! now I finally understood how that system works! Thank you!!:)
That is so helpful! now I finally understood how that system works! Thank
you!!:)
@Elnora4ka You are very much welcome. Glad it helped 🙂
Do you have any videos that are more specific with the mentioning of funny channels/T-type channels/L-type channels and when those, specifically, come into the picture, etc?
Do you have any videos that are more specific with the mentioning of funny
channels/T-type channels/L-type channels and when those, specifically, come
into the picture, etc?
@ruddergrl1 I do not. All the best!
when the level of potassium is high the heart will start beating irregularly , or leads to Cardioplegia,, why is this so,, what is the mechanism that cause the heart to be in this condition
when the level of potassium is high the heart will start beating irregularly , or leads to Cardioplegia,, why is this so,, what is the mechanism that cause the heart to be in this condition
I have a lab exam soon and this helps me.
@madej1858 wow that’s a great grade, congrats!
@zamirahbasher All questions are answered in the Interactive Biology community forums from now on. Go to the website in the description and then visit the community. This is to make it as efficient as possible as we have multiple people over there to help answer questions.
All the best
@HoneiiDiiva Glad to hear. All the best on your exam. Let me know how it went!
Glad to hear. All the best on your exam. Let me know how it went!
@HoneiiDiiva Glad to hear. All the best on your exam. Let me know how it
went!
I like your series of videos but in this case, you really should explain how the Na+/K+ pump works in the pacemaker cell first to set up the potential gradient before the voltage sensitive K+ channels close while the Na+ is still pumped out. At this negative membrane potential, the Na+ starts to flow into the cell against the concentration gradient by diffusion, thus activating the potential of the cell which is the cause leading to -40mV where Ca+2 ions start flooding in.
Funny channels ????
@veganthestephen it flows against the concentration gradient by diffusion, or with the concentraion gradient?
it flows against the concentration gradient by diffusion, or with the concentraion gradient?
@zackboomer Unfortunately, Leslie is busy at the moment with more work to do for the site. He is unable to answer any questions. But, do stay tuned because more biology videos are coming very soon!
Unfortunately, Leslie is busy at the moment with more work to do for the site. He is unable to answer any questions. But, do stay tuned because more biology videos are coming very soon!
great
@gullwings18 Thank you! Stay tuned for more Biology videos coming very soon!
Thank you! Stay tuned for more Biology videos coming very soon!
awesome video 🙂 and you have a cute voice 🙂
@aikatirah Thank you! Please stay tuned. There will be more Biology videos coming very soon!
Thank you! Please stay tuned. There will be more Biology videos coming very soon!
@petercourt The Calcium-induced calcium release by is sequestered back into the SR. The remaining calcium is pumped out of the cell by the Sodium Calcium Exchanger. The sodium is then swapped back out for potassium.
The Calcium-induced calcium release by is sequestered back into the SR. The remaining calcium is pumped out of the cell by the Sodium Calcium Exchanger. The sodium is then swapped back out for potassium.
The Calcium-induced calcium release by is sequestered back into the SR. The remaining calcium is pumped out of the cell by the Sodium Calcium Exchanger. The sodium is then swapped back out for potassium.
All these videos are great. Please keep them coming. You are making learning a lot easier!
All these videos are great. Please keep them coming. You are making
learning a lot easier!
@kingswood331 Oh yes, definitely! 🙂 We will be uploading more videos soon so, please stay tuned!
Oh yes, definitely! 🙂 We will be uploading more videos soon so, please stay tuned!
You are A-Mazing !! These videos help with almost every part of my physiology textbook.
You are A-Mazing !! These videos help with almost every part of my
physiology textbook.
@MissEhouse Thank you! GLad that you seem to be finding value in the videos. Stay TUNED. WE have more Biology videos soon!
Thank you! GLad that you seem to be finding value in the videos. Stay TUNED. WE have more Biology videos soon!
my turban has curry in it
my turban has curry in it
i dont know how u do it but it is clear that u hve a BIg heart….giving free lecture to others.Im a veterinarian and this helps me a lot to recollect the things which i have forgtn
i dont know how u do it but it is clear that u hve a BIg heart….giving free lecture to others.Im a veterinarian and this helps me a lot to recollect the things which i have forgtn
@mlalramhluna Thank you. It’s what Leslie main goal is, to be able to share his knowledge to those who need them. Glad that you’re finding value in his videos. Stay tuned for more Biology fun!
@mlalramhluna Thank you. It’s what Leslie’s main goal is, to be able to share his knowledge to those who need them. Glad that you’re finding value in his videos. Stay tuned for more Biology fun!
Thank you. It’s what Leslie’s main goal is, to be able to share his knowledge to those who need them. Glad that you’re finding value in his videos. Stay tuned for more Biology fun!
Thank you. It’s what Leslie’s main goal is, to be able to share his knowledge to those who need them. Glad that you’re finding value in his videos. Stay tuned for more Biology fun!
Thank you. It’s what Leslie’s main goal is, to be able to share his knowledge to those who need them. Glad that you’re finding value in his videos. Stay tuned for more Biology fun!
The Calcium gate open before membrane reach threshold potential
not till reach threshold potential..
The Calcium gate open before membrane reach threshold potential
not till reach threshold potential..
The Calcium gate open before membrane reach threshold potential
not till reach threshold potential..
Awesome! This helped a lot!
Awesome! This helped a lot!
good stuff well said and it clears up a lot 🙂
good stuff well said and it clears up a lot 🙂
your videos are SOOOOOOOO helpful!!!!!! thank you SOOOOOOOOOOOO much!!!
You are awesome.
@SHFOBA
I believe this is the correct sequence of events:
The T-type Calcium channels open after the funny channels closes, continuing depolarization. This brings the cell potential to the threshold which triggers the L-type calcium channel to spring open, allowing large amounts of Ca++, causing the action potential. I think he just merged both T and L type Ca++ channels together.
I believe this is the correct sequence of events:
The T-type Calcium channels open after the funny channels closes, continuing depolarization. This brings the cell potential to the threshold which triggers the L-type calcium channel to spring open, allowing large amounts of Ca++, causing the action potential. I think he just merged both T and L type Ca++ channels together.
I believe this is the correct sequence of events:
The T-type Calcium channels open after the funny channels closes, continuing depolarization. This brings the cell potential to the threshold which triggers the L-type calcium channel to spring open, allowing large amounts of Ca++, causing the action potential. I think he just merged both T and L type Ca++ channels together.
Shouldn’t there be a plateau phase? Seems like it is more of a skeletal muscle of action potential. Still very helpful though.
Shouldn’t there be a plateau phase? Seems like it is more of a skeletal muscle of action potential. Still very helpful though.
the 2 dislikes are my 2 physio profs
the 2 dislikes are my 2 physio profs
Thank you. This really helps.. as I struggle with class lecture. This puts it all together for me. God Bless.
Hi loved the video, is there any chance that this video is in spanish? I need it to present it in class, thanks!
Hi loved the video, is there any chance that this video is in spanish? I need it to present it in class, thanks!
Thank you. This really helps.. as I struggle with class lecture. This puts it all together for me. God Bless.
Hi loved the video, is there any chance that this video is in spanish? I need it to present it in class, thanks!
what is the cause the voltage-gated calcium channels open when we’ve reached the threshold?
What returns those sodium back out of the cell? They never run out?
What returns those sodium back out of the cell? They never run out?
Excellent! thank you.
Excellent! thank you.
Excellent! thank you.
What about the bundle of His?
What about the bundle of His?
so the Na keeps building up inside the cell and K keeps coming out? Where does it come from?
so the Na keeps building up inside the cell and K keeps coming out? Where does it come from?
thankyou very very much
thankyou very very much
hannah and dana say thanks from CANADA!
hannah and dana say thanks from CANADA!
just want to say thank you for making my life SO much easier ’cause I have an exam thats going to be 18 chapters…I don’t know how I will read it all. THANKS a lot 😀
just want to say thank you for making my life SO much easier ’cause I have an exam thats going to be 18 chapters…I don’t know how I will read it all. THANKS a lot 😀
OMG!!! you PWN my physiology lecturer!!!
OMG!!! you PWN my physiology lecturer!!!
you should come and teach in my university, one of my prfs sucks as
you should come and teach in my university, one of my prfs sucks as
can u make money in biology?
can u make money in biology?
i love the way you say node. NOAD
i love the way you say node. NOAD
I really just need to verify/clarify something: The sodium ion continuously pumps into the cell and never has a period that it changes course and gets pumped out by Na/K pumps??
This seems counter-intuitive – sodium can’t just enter the cells forever without putting a huge osmotic pressure on the cell and bursting it??? Can it?
I really just need to verify/clarify something: The sodium ion continuously pumps into the cell and never has a period that it changes course and gets pumped out by Na/K pumps??
This seems counter-intuitive – sodium can’t just enter the cells forever without putting a huge osmotic pressure on the cell and bursting it??? Can it?
Great vids. BS in bio, prepping for PA school, love these videos. Really great physio refreshers.
Great vids. BS in bio, prepping for PA school, love these videos. Really great physio refreshers.
@1080portal ever heard of physicians? They do pretty well for themselves.
@1080portal ever heard of physicians? They do pretty well for themselves.
Thank you so much 🙂
AMAZING! THANK YOU!
WOW SO COOL
THANKS!
You save my life. I’m a working child and I end up missing a lot of class so these videos really really help me. Plus, you make things easy to understand and give a reason for everything which in turn makes it super easy to follow.
all these videos are great. thank you!
So amazing
biology will never be fun…NEVER.
THANK YOU 🙂 oh this helps me visually . I could not understand what contraction meant (i speak a different language) but seeing the first part now this really helps more than the text book and the lecture audio from my instructor
wow u are amazing!!!!!!! than you from those of us who have bad teachers!!
purkyne tissue he said purkingy fibres ?
simple, concise and easy to understand. Very helpful, thank you Leslie
Very informative and to the point. Thank you
You did a great job. Very very useful.
tnx we need more like u thanks so muchhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh so clearrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr
Very helpful!! Thank you!
A great vedio .. thanks sir (lub-dup:))
Great Video! Definitely helpful, thanks for posting
Amazing videos. Thank you so much. Making my classes so much easier to understand!
thank you soo much for this heart series as i’m really bad at it as my mock proved 😀
Thanks so much for putting this up. Appreciate it so much. Bless you.
I like your vdo very much
Thank you. You just saved me a possible 40 minutes trying to figure out what my textbook is trying to tell me haha, 20 minutes of aimlessly staring into the pages and another 20 trying to read half latin/greek derived words. You display complex effects in simple terms and still manage to include all the crucial information.
Thank you so much for this explanation. This has been tremendously helpful and I cannot thank you enough!
Thank you!! You made it so easy to understand!
You are amazing!!!. Do you have any videos in which you explain the blood types and Rh factor?.
i have an exam tomorrow and this is great! 😀
it helped me alot thank you!!!!! 🙂 u explain it very well 🙂
Thx very much it’s really helpful
perfect! thanks for this effort.
thankxx
lol
Very informative I love your videos, Keep them up
Another helpful video! Thank you!!
Doesn’t the influx of calcium followed by the opening of voltage gated K channels result in a plateau ? I’m really confused – please help!
This is like a skeletal muscles A.P?. Im a little confused my teacher was talking about funny channels, where does that come into the picture?
There are two types of cardiac muscles: contractile muscle cells and autorhythmic muscle cells. Contractile cells make up 90% of muscle cells in the heart and autorhythmic cells make up 10% in the nodes. Autorhythmic muscle cells start the action potentials from the SA and AV nodes that disseminate into contractile cells causing them to contract. InteractiveBiology described the action potential of autorhythmic cells, you described contractile cells. Hope this helped 😛
thank you so much for posting these videos, they’re all very very helpful
You are an awesome individual to take the time to put all these videos. And you make it so simple and easy to understand without getting lost. Thanks MUCH!!
I just love how this particular person gives free lectures plus all the interactive are very easy for me to understand..keep up the good work leslie! You’re making everyone’s life easier 🙂
yes that’s right.. because of the equilibrium
I never understood this fully before, but you make things that much easier to understand. I can’t thank you enough!!!
where´s the funny channel ? xD
thank you so much that was a great help ^^
Leslie? Are you like a biology teacher or something? Maybe you just a nerd. Whatever the case thank you so much sir! I can understand you spoof much more than my cardiac teacher. She might be a super smart retired dr. But, there is something to say a out someone like you that can actually make you understand . I love you voice too. It’s soothing and intelligent sounding at the same time.
Very helpful
Thanks I think I finally understand this 🙂
Have you seen MAD Muscle Ripper? (Google it) It is a quick way for you to bulk up fast.
I love your videos. Thank you for your help!
THANK GOD FOR YOU! VERY HELPFUL
very outstanding teacher love u kisssss u
from where u r
Thank you for your help. I’m a paramedic student and you broke down the depolarizing-repolarizing ion involvement very well for me to understand (we are currently beginning to analyze ECGs).
Very well explained! Thank you so so much!
why is potassium leaving the cell all the time,, doesnt potassium ever come back into the cell ?
when potassium leaves a cell not all of it goes. Its only a percentage change that causes the impulse to occur. So during stages in-between stimulation the potassium does move back in and replenish.
totally helpful。。。thanks
Can I borrow your brain for my exam tomorrow? Lol thanks for the review!
Wow. That was so unbelievably clear. Thanks for making such a complicated concept fun and so easy to understand!
How can K+ only leave and never enter?
Na+/K+pump allows K+ enter and Na+ leave
Na+/K+pump allows K+ enter and Na+ leave
since there’s a higher concentration of K+ inside the membrane then outside, when K+ channels open, K+ will rush out because ions always move from higher concentrations to lower concentrations. The Na+/K+ pump then uses ATP to pump 2 K+ inside the membrane while pumping 3 Na+ outside so that a high concentration of K+ on the inside, and high concentration of Na+ on the outside will be maintained. This also makes the inside of the membrane negative again and return it to a resting potential.
Amazing, in human physiology this semester so this is helpful.
I was taught that there are no functional Sodium ion channels in pacemaker
cells, is this wrong?
nice one!
OMG
Thaaaaank u soo much … u helped me :))))
It seems difficult when my physiology professor say it
but it’s totally easy when u explain it
Bless u ^_^
This video is amazing!!! It is brief but perfectly explain the cardiac electrical activity! Really thanks !