042 How the Release of Calcium Ions Results in Muscle Contraction

Now that you have an overview as to how muscle contraction works, here Leslie now discusses in more detail how it is affected in the presence of calcium. What really happens when these ions are released?

Watch to learn more and enjoy!

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 42, I am going to talk about how the release of calcium ions results in muscle contraction. So, let’s get right into it.

So, here we’re looking at a muscle and there are a few terms that I want you to know. This is called the fascicle, so this section right here, that’s a fascicle and that is basically a bundle of muscle cells. And, this of course then would be individual muscle cells or, as I said in the last episode, you can also call it muscle fibers. What I’m going to do now, is we’re going to take this muscle cell and we’re going to look at it much larger here. Here you can see we have the muscle cell, the muscle fiber and that is made up of these individual myofibrils. So, this would be a myofibril.

We looked at the myofibril in the previous episode and we showed how they’re made up of sarcomeres and I’m going to call a sarcomere from right here, you see this part here, to here, that is one sarcomere. As I said in the previous episode, this is the functional unit of contraction. We’re going to look at how calcium ions is responsible for the contraction of this sarcomere. And, we’re going to look at an animation of how that contraction looks.

So, let’s go to the next slide. Here, we’re looking at the sarcomere and we looked at the parts of the sarcomere. We said that we had a thick filament and that thick filament was myosin, and then we had a thin filament, and that thin filament is called actin.

Now, when muscle contraction happens, it’s because of the sarcomere becoming shorter, this is moving in and I’m going to animate that for you. This is contraction happening, and then the muscle relaxes and it goes back to how it was before. Contraction happens, the muscle relaxes, and then it goes back to how it was before. To put that in perspective, this is me working out in the gym, and as I contract the muscles in my arms, this is what happens. So, my bicep muscles contract, I pull it up, you can see it shortening. The sarcomere is getting shorter. We looked a little bit at how that happens. We said that there are myosin heads on the myosin that actually pulls along and pulls the actin so that this entire unit gets shorter. As the sarcomeres get shorter, and you have many of them along the myofibrils, as they get shorter, the muscle contracts and that causes my lower arm to move up in that direction.

So, now let’s take that and look at a little more detail. So, we’re going back to this picture where we’re looking at the muscle fiber so, that’s this part here again, and as we look at the muscle fiber, there’s something that I want you to notice. Here, we have the membrane that surrounds the muscle fiber and that membrane, we’re going to call that the sarcolemma. Now, you’re probably noticing that I’m using this prefix sarco- a lot. That prefix sarco- refers to the muscle. So, the sarcolemma, the sarcomere… anytime you hear sarco-, you can assume that we’re talking about something relating to muscle. The interesting thing about the sarcolemma is that you have these little openings where the membrane actually goes deep into the cell. And you can see it coming here and you can see it going through there. Where the membrane goes deep into the cell, that is called T-tubules. So, they’re basically these little tubes that go deep into the cell. And they serve a very important purpose. This is how it works.

Last time we looked at the fact that axons come in and make synaptic connections with the muscle cells. This is called the neuromuscular junction. So, when a signal comes down, and it releases the neurotransmitter, in this case the neurotransmitter is acetylcholine, and releases that neurotransmitter, it binds to the receptors that causes the signal in the muscle cell membrane, in the sarcolemma. That signal then travels deep into the cell via these T-tubules and something very important happens. Now, you can see that it looks like it’s one tube that’s going down deep into the cell. But, that tube, I’m going to take that and draw it over here and it’s not by itself. So, here we have the T-tubule and then surrounding the T-tubules, next to the T-tubules, we have the sarcoplasmic reticulum. So, I’m going to draw those here and it’s just going to look like tubes coming down next to the T-tubule. It’s not shown here but, I’m going to show that over here. And, as I said that is called the sarcoplasmic reticulum. The sarcoplasmic reticulum stores calcium ions. So, we have calcium ions inside the sarcoplasmic reticulum. So, let me illustrate that here so, Ca2+, Ca2+, and that’s all throughout the sarcoplasmic reticulum, it’s being stored there for when it needs to be used.

So, once again, we have a signal that’s coming down the axon causing a signal in the sarcolemma. That signal then goes deep into the muscle via the T-tubules. On the T-tubules, we have a receptor that we call the dihydropyridine receptor and on the sarcoplasmic reticulum, we have a receptor that we call the ryanodine receptor. So, let me write those over here. The red is the dihydropyridine receptor (hopefully, I‘m spelling this right) and here we have in blue, the ryanodine receptor. All right, so we have our signal, the signal comes along the sarcolemma, that signal spreads deep into the muscle cell via the T-tubules, that’s going to cause the dihydropyridine receptor to interact with the ryanodine receptor, that it opens the channel and let calcium ions flow out into the cell. Okay so, calcium is flowing out into the cell, out of the sarcoplasmic reticulum, and when that calcium flows out, that then causes muscle contraction. I’m not going to go through all the details as to how it causes muscle contraction in this video but, I’m going to do that in the next episode.

The take-home message is, the signal comes via the axon, causes a signal in the sarcolemma, that signal travels deep into the muscle cell via the T-tubles. Because of the relationship between the dihydropyridine receptor and the ryanodine receptor, that causes calcium that is stored in the sarcoplasmic reticulum to be released, and the calcium released then causes muscle contraction. So, we can look at it here again and we can see here, this is where calcium is being released, and then the calcium is then pumped back out, calcium is being released, calcium is pumped back out.

Now, there’s one thing I didn’t mention and that’s the second part with calcium being pumped back out. You have the T-tubule, you have the sarcoplasmic reticulum, and in the membrane of the sarcoplasmic reticulum, you also have calcium pumps and once the signal is over, the calcium pumps pump the calcium right back into the sarcoplasmic reticulum. So, that’s what’s happening here, calcium being released, calcium being pumped back in, calcium being released, calcium being pumped back in.

That’s all the content for this video. If you have any questions, of course you can ask them in the comments section below, and as usual, you can visit the website at interactive-biology.com for more Biology videos and other resources. That’s it for this video and I’ll see you on the next one.



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  • I hope they would make myo sound like something like luigi in danish, if
    you know what I mean 😛

  • Can you make a video about sensory receptors and their functions? I just cant grasp it when I read the text book.

  • Hi Daniella,

    I actually do already have a video covering that topic. It’s called A General Overview of How Senses Work. It really is what it says – a general overview. If you want to get into more details, you can check out my videos on Vision and Hearing. Just do a search in the search field above.

  • thanks again. it seems everytime u upload a video im at at the same spot.
    right now we’re learning about heart contractions like diastole and
    systole. but this muscle video will be helpful review for the test in 2
    weeks!

  • At 0:36 you said “fasicle”, but I wonder if it should be “fascicle.” I think your videos are great! Keep up the good work!

  • @smogavc123 Thank you. I’m using Keynote on the mac as the presentation software and Screenflow to record my screen. They are both Mac-only programs. If you want more details on how I do it, send me a private message and I’ll send you more info.

  • this is the very best video about muscle contraction on the web. I was very confused before and now all my questions are answered. thank you from the bottom of my heart.

  • ur vidio is perfect do have any vido about about cori cycle or glycolysis cycle ? if u have plz send me the web site?thanks

  • That’s explained in Episode 43. I see you left a comment there, so I assume that you got the answer 🙂

  • Glad we’re able to help 🙂 Please stay tuned. WE have more Biology videos to be uploaded very soon!

  • Hi dude..awesome moovies that helps alot during the exampreparations…I just wonder what happens in a eksentric phase when the muscle is working in both phases..?

  • Hi dude..awesome moovies that helps alot during the exampreparations…I just wonder what happens in a eksentric phase when the muscle is working in both phases..?

  • @lofo87 Thanks for watching! Unfortunately, Leslie is too busy right now working on his site. Because of the overwhelming number of emails sent to him everyday, he’s not had the time to get to each of them. He’ll be adding more Biology videos though and will be tackling more topics and othe body systems. So, please stay tuned!

  • Thanks for watching! Unfortunately, Leslie is too busy right now working on his site. Because of the overwhelming number of emails sent to him everyday, he’s not had the time to get to each of them. He’ll be adding more Biology videos though and will be tackling more topics and othe body systems. So, please stay tuned!

  • That’s awesome! Glad to know the videos are helping a lot. Please stay tuned. We have more Biology videos coming very soon! 🙂

  • Hi dude..awesome moovies that helps alot during the exampreparations…I just wonder what happens in a eksentric phase when the muscle is working in both phases..?

  • Thanks for watching! Unfortunately, Leslie is too busy right now working on his site. Because of the overwhelming number of emails sent to him everyday, he’s not had the time to get to each of them. He’ll be adding more Biology videos though and will be tackling more topics and othe body systems. So, please stay tuned!

  • thank you so much you helped me pass my biology test 🙂
    love you! keep uploading and helping!

  • Wow! That’s excellent 🙂 Definitely we’ll be uploading more so, please stay tuned for new Biology videos coming very soon!

  • @mstice88 Hi! That sounds excellent! We’re so glad we were able to help and that you’re finding value in them. You can find more of the videos at Interactive Biology. You’ll see a complete list of Leslie’s Biology videos. See you there!

  • Hi! That sounds excellent! We’re so glad we were able to help and that you’re finding value in them. You can find more of the videos at Interactive Biology. You’ll see a complete list of Leslie’s Biology videos. See you there!

  • Hi! That sounds excellent! We’re so glad we were able to help and that you’re finding value in them. You can find more of the videos at Interactive Biology. You’ll see a complete list of Leslie’s Biology videos. See you there!

  • if possible, i ll like you to explain on smooth muscle #and its actions. thnks alot

  • Thank you so much, these videos are really helpful, its a quick recap of what we study in books and being a medical student these videos are a great help when I am looking for a quick review of basics.

  • Thank you so much, these videos are really helpful, its a quick recap of what we study in books and being a medical student these videos are a great help when I am looking for a quick review of basics.

  • You are the KING!! You totally just saved me – have a huge physiology test tomorrow, and even though I have to be up in like 3 hours, i’m beginning to have HOPE!!! 😀 THANK U! Subscribed.

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  • #BS1006 Since I was very confused about calcium in muscle contraction
    after Monday’s lecture, I decided to take the matter to YouTube. The below
    video cleared most of it up for me since some of the diagrams in the
    lecture handouts are a bit confusing. In addition to describing the calcium
    release process the video also explains that calcium is not released by the
    SR itself but by the terminal cisternae of SR.

  • Man I got from ur video more than what i got in my lecture for more than 9 hrs. Also, u gave the cool animation and uwith ur drowing u gave very clear tutoreal. Thanks Alot 🙂

  • Man I got from ur video more than what i got in my lecture for more than 9 hrs. Also, u gave the cool animation and uwith ur drowing u gave very clear tutoreal. Thanks Alot 🙂

  • ur amazing..i never understand this term in my class but now after watching this video i learn so many thing..thank yu soooo much ur best..just want to know u have lecture on biochemistry???

  • ur amazing..i never understand this term in my class but now after watching this video i learn so many thing..thank yu soooo much ur best..just want to know u have lecture on biochemistry???

  • Thank you so much sir! Understanding this concept by reading the textbook was giving me a headache. Thank you for simplyifing the process.

  • Thanks for your nice presentation.
    it was one of my problems in biology for many years and I coulden’t memorise the whole process.
    I really appreciate you.

  • My professor sucks and only puts pictures on his slides! He made us buy an outdated book and never explains anything! You totally just helped me understand this concept with just one view of this video! Thank you SOOOO much!!!

  • Does depolarization of the sarcolema occur before or after depolarization of the T-tubule?

  • thank you! Im not even done watching the video but it already helped me understand more

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  • SHEONA! STOP SHOWING THIS VIDEO IN YOUR ANATOMY CLASS!

    p.s please make me pass anatomy this year

  • Yoo who just saw that commercial before the video with the Poe injector thing? Weird…

  • Could you explain the function of the presence of Magnesium in Calcium restriction in muscle contraction please?
    Warm wishes.

  • Thank you! Your videos are incredibly helpful and it’s clear that you are passionate about making this information understandable. You are a wonderful teacher..

  • WOWOW JUST WOW. I DIDNT UNDERSTAND anything my lecturer woman thought me at university about this. and it covered a whole chapter of textbook. YOU JUST SMASHED EVERYTHING BACK INTO MY MEMORY VERY EASILY THANKS 😀 REALLY!

  • Hey guys. Fine vid. My cousin had been flabby. He went from 284lbs of pure fat to 201lbs of purely natural lean muscle. I could not believe it! I just subscribed myself coz I wanna strengthen. He made use of the Muscle Building Bible (Google it)…

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  • Thank you SO very much! This will help me on my short answer for my test. I appreciate how you explained it.

  • Thank you SO very much! This will help me on my short answer for my test. I appreciate how you explained it.

  • Thank you for your videos,
    I have a question please, are the muscles receives one signal from the neuron or it’s continuous signal during the contraction. ..regards

  • If you want to get you a well-defined body, you must Google “Oak Muscle Method”. You are certain to get the appearance you desire.

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  • Thanks for the vid, this helps a ton with understanding how it all works. Now quit using those dumb machines in the gym!! Use freeweights, barbells or do bodyweight exercises.

  • yes i mean it. even i was very sad since i workout well for abs but nothing was coming. And I saw an interview with body building champion where he talks about 7 odd foods he eats to keep his abs hard. i found it here bit.ly/16ZDCqR?=eeovb

  • It would be a shame if you did not get ripped when these people bulk up easily using “Rapid Muscle Booster” (Google it).

  • Hey hi you doing I just finished watching your video,,,I was wondering can a muscle stay elevated or in contraction from calcium ions not releasing and is there a way to get the muscle to relax.

  • Yep I agree. even i was very sad since i workout well for abs but nothing was coming.

    btw!but ye the surprising part is my friend who is not doing much excercises, maintaining his six pack with this secret food items.

    worth watch here now bit.ly/1dexJOd?=bqkxn

  • Yep I agree. even i was very sad since i workout well for abs but nothing was coming.

    btw!but ye the surprising part is my friend who is not doing much excercises, maintaining his six pack with this secret food items.

    worth watch here now bit.ly/1dexJOd?=bqkxn

  • Yep. before I started eating right it didn’t matter how much I exercised my abs were still jello.

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  • what does the terminal cisternae do? and are they represented by the blue lines you drew beside the t-tubules (red lines) ..the video annotation about the terminal cisternae confused me lool…. thank you though, I didn’t understand a word my lecturer said but you made it seem so simple…great video!!!

  • Hello everyone. Fabulous video clip.

    My good friend was once a fat. He converted himself from 293lbs of pure fat to 204 lbs of genuine lean muscle mass. His mates were in shock. I just signed up myself as I wanna strengthen. He made use of the Muscle Building Bible (Look in Google)…

  • That was a whole lot of video for a very very small piece of information… lol. Maybe pre-draw a lot of stuff to move along faster and get to the mail lesson.

  • So its Terminal cisternae instead of T-tubule and if I m wrong please
    clarify. nice videos 🙂

  • The muscle action potential will cause the sarcoplasmic retoculum to
    release calcium ions when stimulated directly by what?

  • I understand the concept of calcium in muscle contraction, but what role does cl- plays in muscle contraction

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