Action Potentials and Contraction in Cardiac Muscle Cells

[@walidrahman2]

I was failing one of my biology classes until I found your channel. You are amazing at explaining everything.

[@MsBRETTB]

Wow! Your passion makes me learn this stuff even more! You have a gift, thanks for making this so manageable!

[@MegaSeany11]

Your voice is deep, velvety, and silky smooth my man, Definitely making biology fun.

[@iren181]

100% True

[@bigdog4574]

You missed Phase 0- Phase 1 transition where fast Na+ channel closing, creates initial drop in Em. Phase 2 is the Plateau from the L-type Ca+ channels being open as a result of Depolarization, same time IKr channels are open that pump K+ out of cell. That is the reason for plateau because K+ out off-sets Ca+ going into the cell. Influx of Ca+ causes Sarcoplasmic Reticulum Ca+ release, this reults in cross-bridge cycling & muscle contraction. The Plateau is the ST segment of ECG. Overall this explanation requires a few more additions to be correct.

[@InteractiveBiology]

@petercourt You are very much welcome. You are correct. The bundle of His actually branches off into the Purkinje fibers. Those fibers are the little branches you see. Sorry, my line was a bit off when pointing to the purkinje fibers.

[@iren181]

Thank you so much !!!! i'm an occupational therapy student in uni and this was amazing helped me a lot.

[@Ray24393]

Awesome! Thank you sooo much for these amazing videos. Textbooks make it so difficult to understand but you take very difficult material and concepts and actually manage to make it understandable in less than 10 minutes! God bless you!!!!!!

[@Nickmysterthe8th]

WOW...I Love you. Got a test tomorrow and this was the thing i was struggling with for a while.

[@azila00]

Thank you so much. I had difficulty before watching this episode. This episode has made it so easy for me to understand about action potential and phases of cardiac muscle contractions. Once again thank you very much. God bless you.

[@AshwiniKumar]

there is also a phase before Plateau phase, and that is Early Rapid Repolarisation, in which the membrane potential reaches to 0 mv, for opening of L type Can channels, which is necessary for the stimulation of SR Ca channels.

[@jameelksingh]

Used this to study for my MCAT. Very good videos. Will be looking for Kidneys next lol

[@Singingshayna]

You're videos so unbelievably helpful. Thank you so much for being such a genius but still being able to relay the information!

[@InteractiveBiology]

@jessicg61 Hi! Unfortunately, Leslie won't be able to answer specific questions as he is busy with a lot of work. He will definitely get to more systems in the future. He has many to work on at the moment. So stay tuned for more!

[@israahmadahmad916]

No comment..... just Brilliant!!

[@noedetteperpetua5395]

I love you lesley. You make physiology really easy for me

[@provitaminjets]

man your freakin amazing man! i've been watching your videos and mastering human phys. every time i have an epiphany, and convince myself something is one way, i watch your videos and you clear things up. really appreciate your dedication, live from central canada thank you very much sir.

[@priscillaalameda6339]

Will appreciate it if the Bundle of His was also mentioned...Thanks! =) The videos are REALLY helpful. Good job!

[@petercourt]

Thanks for the video! Very helpful. But isn't the part you've labeled Purkenje the left bundle branch of His?

[@suzana00]

Thank you from the SA node of the heat of tired med student ♥️

[@InteractiveBiology]

This was my favorite comment for the month 😂😂😂

[@brumified]

@anas lahrichi The bundle of His is a cluster if specialised conduction myocardiocytes, they transmit that electrical energy from the AV node to the Purkenje Fibres; so they function to transmit charge Moreno than concentrate it as in the AV node cardiomyocytes.

[@anaslahrichi]

Where is the bundle of his located ? Has it the same role ?

[@jessicg61]

what is the "extra event" that occurs in cardiac muscle?

[@Mobimobipopo]

Does The action potential includes Depolarisation phase and the plateau?

[@umarecol81]

wow this video helped me so much, it made is so much simplier to understand! Thank you so much!

[@mrmikeymills]

Depolarization lasts less than a ms in skeletal muscle cells? I don't think so... Also, the calcium is not released from the Sarcoplasmic recticulum until voltage gate Ca2+ channels open, allowing EXTRACELLULAR Ca2+ to enter the cell (this is the nature of the plateau), triggering ryanodine receptors to open the gate of the Sarcoplasmic recticulum. Once this happens, then Ca2+ is released from SR, causing calcium spark and triggering the events of the power stroke (muscle contraction).

[@sabah1242]

the videos are really good for revision! thankyou! can i just ask tho, in smooth/skeletal muscles, calcium is released aswell from the sarcoplasmic reticulum so why doesnt that result in a plateau phase..? is it to do with the timings, because action potentials are time dependent also?

[@HyperAmygdala]

It's 3am,exam at 10:30am. All I can say is Thank You!!!

[@jj4penguin228]

Is calcium also release by the terminal cisternae in Cardiac muscle?

[@smitabhatia]

Much of the calcium in cardiac cells comes from the ECF, in addition to what is released from the SR. In fact, calcium released from the SR is due to the calcium that comes in from the ECF ( Calcium-induced calcium release)

[@spechalboy91]

Excellent video. A great refresher for me. Thank you!

[@babaikarmakar8501]

Video uploaded 11years ago 😱 .... NICE VIDEO SIR 🙏

[@InteractiveBiology]

Thanks. I guess the way the heart functions hasn't changed in 11 years 😀

[@Bindasjhakyass]

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

[@InteractiveBiology]

@cid6000 You're very much welcome!

[@marianb2530]

Thank you so much! I thought this was going to cover PQRST....

[@InteractiveBiology]

I cover that in this video - kzbin.info/www/bejne/inq2g2mIiJuae6s

[@pagurotraduzioni202]

HI, there. Thank you for this video. What is the difference between the red and blue curves. I did not get that very well. Makes sense to highlight their difference? Is it the membrane potential vs. the tension in the cardiac muscle cells?

[@InteractiveBiology]

@CecilieWhipps We love saving lives. Especially with Biology ;)

[@muhammadericali]

why does K+ ion release cause muscles to relax? Really helpful video!! God bless you.

[@oliverwilliams88]

M Ali Under physiological conditions, K+ ions will move OUT of their channels (efflux), which is the opposite for Na+ and Ca+. Therefore, the loss of charge from the cell from K+ efflux will bring the membrane potential down (make it less positive) which will terminate action potential spikes (once sufficiently below threshold) and in turn terminate muscle contractions.

[@steveschneider2356]

hi,thanks for this amazing video .however i wanna tell u that the calcium ions enter the membrane of the fiber in the heart .Not released from the endoplasmic reticulum as u mentioned .this is true in skeletal muscles but not here in a myofiber of the heart

[@hilarydirks715]

Actually both happen. It's called Calcium induced-Calcium release. It's unique to the cardiac cells.

[@sozana121]

Great! i hav an exam after tomoroow i needed this thanx

[@DendeSillyBeast]

these viedos are fantastic for review :)

[@imeldaflores9905]

thank you. these videos are amazing and have been so helpful

[@Erykkan]

you didnt mention movement of inons in different phases...

[@kerryvp]

Are you a Trini?? Good stuff!

[@natazyasvetlana5219]

Thank you Sir!! this helped me a lot!!!

[@InteractiveBiology]

@lovelylatina207 Thank you! Stay tuned for more Biology videos coming very soon!

[@sandy40776]

thank dude because of u all concept r clear

[@rishmaakhtar1381]

Link of episode 42 ....please send

[@InteractiveBiology]

Sorry for the delayed response. Here you go - pulse.ly/bawg7xglcm

[@hatsamb]

If calcium is also released in skeletal muscle cells, why is there no extended refractory phase there...

[@JL6293]

This is a fantastic question, and I think using graphs would be the best way to explain. But since I have no visual aid, I hope to point you in the right direction: So - I think thing we're confusing here is skeletal MUSCLE depolarization and the NERVE depolarization. The muscular depolarization of skeletal muscle lasts a long time compared to the instantaneous depolarization/re-polarization cycle (action potential) of a muscle's associated nerve.

[@rounikt]

@Anumanu1711 -------absolutely crrct......the early repolarisation phase is missing here....... that produce an inword notch in graph just before onset of plateau .......due toactivation of a trascient outword current carried mainly by k+(efflux of k+)

[@brumified]

Moreso* Also they extend directly from the AV node

[@alexrn8577]

thank you, that was great demo

[@imanesmaili5519]

Thank u so much for these videos

[@ldyluv6988]

THANK YOUU SO MUCH FOR THIS! i UNDERSTAND THIS NOW!!

[@InteractiveBiology]

@NeedsAHardOne Thank you! :)

[@Emmalicourice]

this video rocks! thank you!!

[@packerfan43042]

Very great videos! Greats Appreciated.

[@hunger4jsutice]

Why does Ca cause the release of aceytylcholine and cause muscle contraction, yet excess calcium results in muscle weakness? Can you tie that in with the action of Ca channel blockers and their negative dropotropic and inotropic effects? Thank you, and I love your videos.

[@hunger4jsutice]

I do understand the Ca channel blockers decrease vascular resistance, causing dilation and thus the afterload is reduced, so that results in a negative inotropic and dromotropic effect. I guess I am confused about the seeming paradox of hypercalcemia causing muscle relaxation/weakness and yet calcium as a cause of muscle contraction and vascular resistance.

[@thealmassi1]

Yes. AP ends once it reaches the resting potential again.

[@bruisedvein]

this is most excellent

[@SuperM3aned]

you are my hero doctor

[@cid6000]

Thank you

[@fengyi07]

I agree with steve schneider

[@delijeceber]

Hello! I am from Greece and I am studying Biology in Germany. Your videos are really very very helpful!!! I have a stupid question though: does the plateau phase exist only at the cardiac muscle cells or generally at every muscle of the body? I mean, it sounds logic because there is a Calcium release at every muscle...

[@GabbyLagemann]

Plateau only in cardiac muscle. It prolongs the action potential to as long as 300 msec. This prolongation plays a role in triggering muscle contraction. Recall that in skeletal muscle if the frequency of action potentials is high enough the muscle will enter a state of tetany in which the muscle remains continually contracted. If this happened in the heart, blood flow would stop, since refilling of the chambers requires that the heart relax. Also, contraction of cardiac muscle requires the contribution of extracellular Ca2+. All during the plateau phase Ca2+ is entering the cell from the extracellular fluid, contributing to total intracellular calcium concentration.

[@Mrpimp490]

what was the difference between the red and the blue curve. I got that the blue curve represent the cardiac contractile muscle AP but what was the red curve for. it confused me a little

[@thealafond]

blue is the contractile response so how the muscle reacts to the action potential

[@americanenglishazerbaijan]

Perfect !!!!!

[@nabilmnooortaha]

thank you very much

[@jessarennie5920]

Thank you a ton!!

[@264amdx]

Thanks a lot mate

[@mirrorreflex]

Also if the heart did have tetanic contraction it would fatigue, which we do not want as our heart is needed all the time.

[@Scoffstache]

gives time for ventricular filling and prevents tetanic contraction

[@bomhayhay]

Thank U

[@muhammadjunaidali769]

Awesome

[@InteractiveBiology]

@kerryvp St. Maarten :)

[@belanabdulla6368]

👏👏

[@vincentgogh2389]

Wronggggggggggg!!!

[@leena969]

Thank you