Your drawing is so much better than any video. I love how you literally broke it down. Sincerely, struggling BIO student, SC.

Perfect explanation, particularly in terms of relaxation at the end, nowhere else seemed to explain that. Such a simple part, yet a full explanation is needed. Many thanks!

you are the man! the marker ATP analogy really made sense. thank you!

Thank you for these videos! Very helpful for understanding this stuff...sometimes one lecture during class isn't enough. It's nice to be able to watch over and over again, pause, and take notes.

Makes complete sense! I wish all teachers were as caring and thorough as u!

This is better than any of the animations that I have seen so far. Thank you!

Dude. This helped me so much more than any animation that I watched. THANK YOU!

Thank you so much for this video! I was totally stumped with all the A-lines, Z-lines (discs) and bands and how it all works together. You Sir are an awesome teacher!

Yes, I goofed up from 3:30 to 3:58. After that short bit it's correct. Just for clarity --> Calcium binds to troponin causing troponin to move tropomyosin off of the myosin binding sites on actin.

Thank you! I wish every professor was as passionate about teaching as you are! Keep it up!

I'm not even in your class but saw the video and helped me understand this theory a lot easier. Especially with the ATP marker analogy. Thanks!!

You did an awesome job with explaining that. Really don't even need an animation. The marker cap analogy worked. Thanks.

This is the only video that has made me understand sliding filament theory

Thank you Dr. Hartung for these group of videos. I finally understand muscle cell anatomy and physiology.

My A&P teacher does a really bad job of explaining things to us. I just wanted to say thank you for taking the time and explaining things so us struggling a&p student have a fighting chance to succeed! :)

i want you as my teacher. all your videos are so easy to understand!! thanks alot

i had watched around 10 animated videos but this is much better than anything else

Your explanations were clear and straightforward. Thanks for posting!

Man you are an excellent teacher. I felt like such an idiot in class. You just made it all make sense. Thank you so much. You rock

Thank you for getting back to me so soon. Yay I feel smart, maybe I will do great on my test. Wanted to add your lectures are very helpful. Thank you for putting them put there for us!

OMG YOU JUST SAVED MY GRADE BIG TIME. Thank you for taking the time to do these videos. You've helped me more in one night than my professor has all semester...

excellent not even the other videos explain the way you did thanks a lot

This video helped me in understanding the sliding filament. Thank you soooo much. :)

Your truly amazing sir..I have learned more form you in 10 minutes than I did for 1 hour from my Professor at Stony Brook!

Thank you, renhartung. This really helped me understand the process. You do a great job clearing up holes that I didn't get in class. :)

You're the best Dr. Hartung!! My exam is today i will love you for this

Thank you for your help !! I finally understand the sliding filament theory !! You're a great teacher !!

Love the way you explain everything! Did you do a video on the cross bridge cycle? I looked through your uploads but didn't see anything. Wasn't sure if maybe you added something about it to another video. Thanks!! =)

great job at explaining this! really was unsure of how this worked! i have a better understanding now.

Thank you. You've completely cleared this up for me.

you are a legend, thanks for the help you have done so much better then my other teacher at teaching me this!

This is the best video. you did really good job. thanks a lot

You are an amazing teacher! Thank you! Post more! :)

Thank you SO MUCH! This video definitely helped me better understand!

Fantastic video. Thanks so much for your help.

I think this was a GREAT video!!!! So helpful!!!

Thanks so much. The drawings really help me understand the information much better.

video helps alot! i wish i would have seen this before my exam! this will definately help me retain this information better for the future!

that was so easy and simple . Thank you Dr.

Thank you. I am surprised that nobody else mentioned that before, and that I have been missing the error for a year :P Thank you again for catching it.

You are fantastic and so helpful! Thank you do much!

Thank god I found u. u saved my life

I was struggling with this concept. Thank you, you are a good teacher! Very helpful to use the marker/cap for ATP/P.

You did a great job.Even though i am a Chinese, its no problem for me to understand this. Appreciated.Well done !!

This was very very helpful!!!! I understand it so much better than in my lecture!

Great video! Thanks professor.

Thanks so much! I have test on Monday and I thought I wasn't ever going to understand this! Your video really helped alot!!

Great video, makes so much sense now.

This is helpful. Thanks Ren Hartung.

This is a really great explanation of the sliding filament theory! There are so much strange 3-D animation video's about this subject. Most of those video's are hard to understand when you need to know the basic concept of the sliding filament theorie. Thanks for the video, it helpt me a lot to understand the basic proces of muscle contraction!!

This is great, really good stuff! Thanks a lot! Greetings from Antwerp(Belgium)

thanks man! really helped my understanding!

Wow what a great explanation! Thank you.

wow those 2 vids are so great!!!

Finally understood excitation-contraction coupling, thank you!!

You helped me a lot!

thanks. clearly demonstrated and understandable ..

That was helpful, thank you!

Thank you, I have a better understanding now.

thank you! very good explanation!

I had no clue what I was reading and looking at in the textbooks, thank God for these videos or I wouldnt understand ANYTHING. I just wished I would of found these videos when I was study

Thank u very much doc:) your video posts are very usefull:)

yep ur awesome thanks so much got my exam this week and i didnt have a clue about this....uve just made life so much easier..mwah x

You are awesome Doc 👍👍

Question. You said the calcium binds to the tropomyosin, I thought it binds with troponin causing the tropomyosin to move exposing the myosin actin site?

Sweet! Thanks! I'm subscribing, cuz i might need help throughout this year before i graduate!

awesome video! very helpful

thank you soo much! very helpful!

The binding and release of ADP+P and ATP with relation to the movement of myosin is tough!!! I think you did a very good job explaining it though. Thanks!

Robin Guyor -- For some reason I can't reply to your question directly, but you asked about cross bridge cycling. The sliding filament theory includes cross bridge cycling. Cross bridge cycling is what happens as long as the binding sites on actin are exposed and there is ATP around for the myosin head groups to do their thing :)

thank you! your videos are great! I wish you were my instructor. Please make more videos!!!

Thank you this is fab! But is there a link for the alternative animations you mentioned at the beggining as I can't seem to access the playlist please? :)

Thank you so much.... major lifesaver!!!!

Your book is correct. The binding of Ca++ to troponin causes troponin to change its shape. Troponin is bound to the tropomyosin such that when troponin changes its shape it causes tropomyosin to move off of the myosin binding sites on actin. My explaination may be a bit more detailed, but it's basically the same as what you got from your book :)

thanks for this video it is helped me too much

Great video. I'm in an A&P class at Weber State in Utah, and your explanations help me clarify the whole process. One note, and I'm sure someone has already pointed it out, but when you first start mentioning troponin and tropomyosin, you do say it backwards the first few times. You say that calcium binds to tropomyosin and moves troponin off the actin binding sites. It does get corrected later, but you never clarify in the video that it was backwards. Just thought that might help others :)

finally understand! thank you!!

thanks a lot sir, for making so easy ....

Thanks for the video. To fix the error in the video: Before myosin cross-bridges can flex, they must first attach to the actin filament. When the sarcoplasmic reticulum is stimulated to release calcium ions, the calcium binds with troponin, a protein that is situated at regular intervals along the actin filament and has a high affinity for calcium ions. This causes a shift to occur in another protein molecule, tropomyosin, which runs along the length of the actin filament in the groove of the double helix. The myosin cross-bridge head now attaches much more rapidly to the actin filament, allowing cross-bridge flexion to occur. It is important to understand that the amount of force produced by a muscle at any instant in time is directly related to the number of myosin cross-bridge heads bound to actin filaments cross-sectionally at that instant in time.

great video thanks a lot

Acetylcholine is the neurotransmitter for skeletal muscle contraction. Look at the video on excitation contraction coupling. This video on the sliding filament theory is picking up where the video on excitation contraction coupling left off :)

Really nice explanation

awesome video

That is my understanding :) The myosin head forms a myosin cross-bridge when it binds to actin. However, some instructors use the terms "myosin head," "mysin head group," and "myosin cross-bridge" interchangeably.

You are great, thank you so much :]

Amazing explaination 😄😄😄 Thank you Dr

Hi. Great video and explanation. As far as I was aware, the myosin head doesn't become a 'cross bridge' until it is bonded to the exposed binding site on the actin?

I wish you would of mention something about the role of magnesium concerning muscle relaxation

You are amazing😊.. Literally u made things much easier.. Thankss a lot teacher.. Now i need not to go anywhere else 👍

@zay2ne Yes... Ca++ binds to troponin... troponin then moves tropomyosin off of the myosin binding sites.

thank you so much...

THANK YOU!!!!

sir thank u so much u help me much it was realy hard to me but now i got

My professor said that once the SR stops the secretion of CA++ that "reverse ratcheting" occurs. Is that what happens? our does The myosin head basically "let go" and Tropomyosin covers instantly? or does the Mysoin retract backwards b4 the muscle returns to rest?

Excellent video...I honestly learned it all from you thank you.... One thing that I'm not sure of that is the leaving phosphate; does phosphate leaves the myosin head without ADP or does it leave with ADP...... I just think that both of them should leave so that ADP doesn't accumulate on the head and keep the process consistent ....

my understanding is that once Ca++ levels get low enough the binding sites get covered by tropomyosin again so that the myosin heads can no longer bind. Within that particular muscle fiber (cell) the myosin can't bind so the cell goes completely flacid. However, if other muscle cells in the muscle are still firing, but not with enough power to contract, they likely undergo some kind of reverse ratchet activity. I would ask your prof. to clarify what they mean by reverse ratcheting.

thank you!

Oh god I love youtube. My best friend through college years!

thanks for this video I finally understand :)

This helped me!! But where is acetocholine involved in all of this?