051 Isovolumetric Contraction

Isovolumetric contraction is that stage when the ventricles continue to contract even though the blood volume stays the same. How and when exactly do this happen?

Watch to learn more.

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 51, I am going to talk about isovolumetric contraction. So, let’s get right into it.

What we’re looking at here is diastole at the top and systole at the bottom. So, this is where the ventricles are relaxing and this is where the ventricles are contracting. As you can see, blood is flowing into the atria and then, into the ventricles. Then, when the ventricle contracts, that pushes the blood into the aorta so that, it can go to the rest of the body and also, send blood to the lungs.

There’s something very significant that’s happening here. When the blood comes in, you can see this atrioventricular valve is open to let that blood get in to the ventricle. Once the ventricles contract, that causes this atrioventricular valve to close and of course, the same thing over here, so that the blood does not flow back into the atria.

We see here that this semilunar valve is open. However, that does not happen immediately. When the ventricle contracts, it needs to build up enough pressure to open that valve so that, the blood can flow out of the ventricle and to the rest of the body.

What we’re going to look at over here is what we’ve looked at before where right after the ventricular contraction happens, the cycle starts over and the ventricle fills with blood. So, you’re going to see an increased volume in the ventricle. And then, at a certain point, the atria are going to contract so, when the right atrium contracts, that forces even more blood faster into the ventricle. So, when the left atrium contracts, that forces more blood faster into the left ventricle and then, the ventricle contracts. When it contracts, that is going to push blood out of the ventricle and it’s going to go to the rest of the body. This is the end diastolic volume here and here we have the end systolic volume.

Let’s look at what’s happening in the ventricle when it comes to pressure. During the relaxation period, the diastole, we’re not going to have any pressure in the ventricle. So, we hardly have any so, I’m going to put that around zero. Then, at a certain point, let’s say at this point here, we have the atrium contracting, and when the atrium contracts, that’s going to cause an increase in pressure in the ventricle. Not a huge increase, but, an increase nonetheless. Then, the ventricle is going to contract. When the ventricle contracts, that’s going to cause an increase in pressure in the ventricle.

Let me draw that here. Here, we have that increase in pressure but, as you can see, it’s not until we reach this point that the valve actually opens, the semilunar valve opens, so that the blood can flow out. This is the point that we need to reach. Let’s say that that point is somewhere around 80 mL of mercury so, the pressure has to reach approximately 80. When that happens, the semilunar valves open and the blood gets ejected. We still have some increase in pressure and then, at a certain point, the muscle relaxes, we get diastole, and the pressure comes back down.

This time period, between where the ventricle contracts but the blood does not get ejected, and this point, we call this, (let me do that in a different color), we call this isovolumetric contraction. Why do we call it isovolumetric contraction? “Iso-” refers to the fact that it’s the same; “volumetric ” refers to volume so, the volume stays the same; “contraction” because the ventricle is actually contracting even though the volume is staying the same. The reason the volume is staying the same, is because the valves are closed so, the blood cannot leave until it reaches that point where the semilunar valve opens. Once that opens, the blood can flow out to the rest of the body.

That’s it! That’s the concept of isovolumetric contraction. That is all I want to cover in this episode. As usual, I’d like to invite you to visit the website at Interactive-Biology.com for more Biology videos and the many other resources we’re adding over time. Our goal is to help make Biology fun. That’s it for this video and I’ll see you on the next one.



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  • Leslie,

    I am a UK medical student, and am currently studying for exams. I came across your videos on YouTube, and have been extremely lucky to do so. I found the videos on pacemaker potential, action potentials and adrenaline extremely useful. These concepts had been covered in great depth in both lectures and tutorials, but never had I been so confident, until watching your videos.

    I think what you’re doing is wonderful, and really appreciate it. Keep them coming!

  • Wow, that’s awesome to hear G,

    Thanks for your comment. I’m so glad that the videos are able to help you that much. I will most definitely keep them coming!

    All the best!

  • This site is fantastic!! It really brings the dull (sometimes difficult to understand) words in a book to life. I am currently taking physiology which is not a simple course, but this site has helped me better understand what I am learning. Do not get me wrong, science in general is fascinating, but difficult and as I said this site makes it easier and much more fun.

    Thank you for taking the time to put together such a wonderful site and offering this knowledge to students. I, as I’m sure many others greatly appreciate this!!

    Best regards,

    Scott M.

  • That’s awesome to hear Scott. Glad to know that the site is helping you so much. I hear ya. Science CAN be difficult to understand at times. But hey, if you break it down piece by piece, it all comes together.

    Thanks for your feedback!

  • Hi Leslie,

    I am studying physiotherapy and I am soooo glad I came across your site!
    I understand concepts that I have had explained by lectures but never quite mastered until now. Thank you!

  • Hi Shireen.

    That’s awesome to hear. Glad to know that the videos are helping you that much. All the best with the rest of your classes.

  • Hi Leslie,

    wow Awesome brother! keep it up! Wonderful videos! very easy to understand!

    Thank you for your time and for sharing such great knowldge with us!I must tell you biology is very difficult subject but you made it so easy.
    so thank you for that!

    Cheers

    Hiko

  • Hi Hiko,

    Thank you so much for taking the time to leave that comment. It’s great to know that people are finding value in the content.

    Stay tuned, because there’s much more to come.

  • Thank you so much for these videos. I am currently in an Anatomy and Physiology class and these are helping to understand (and appreciate) some of the more difficult concepts. Keep up the great work… I’ll be staying tuned!

  • Desiree, that’s awesome to know. Glad the videos are helping you. Definitely stay tuned because there are many more coming 🙂

  • at 1:51, you say that “the ventricle fills with blood”, and then you draw an increase in volume on the systolic graph. but then you say (at 2:01) that “then the atria are going to contract… and that forces even more blood into the ventricle” and then you draw another another increase in volume in the ventricle. i’m wondering how the ventricle fills with blood the first time (from 50mL to ~105mL), and BEFORE the left atrium contracts? you seem to make a distinction between them

  • at 1:51, you say that “the ventricle fills with blood”, and then you draw an increase in volume on the systolic graph. but then you say (at 2:01) that “then the atria are going to contract… and that forces even more blood into the ventricle” and then you draw another another increase in volume in the ventricle. i’m wondering how the ventricle fills with blood the first time (from 50mL to ~105mL), and BEFORE the left atrium contracts? you seem to make a distinction between them

  • @Medulaman683 Great question. The blood is actually coming back to the rest of the body. There are skeletal muscle pumps surrounding the blood vessels and are involved in bring the blood back to the heart. Since the A.V. valve is open, the blood can just basically flow back into the ventricles. Then when the atria contract, that gives the final “push” for the rest of the blood that enters the ventricles. Hope that helps.

  • Great question. The blood is actually coming back to the rest of the body. There are skeletal muscle pumps surrounding the blood vessels and are involved in bring the blood back to the heart. Since the A.V. valve is open, the blood can just basically flow back into the ventricles. Then when the atria contract, that gives the final “push” for the rest of the blood that enters the ventricles. Hope that helps.

  • Great question. The blood is actually coming back to the rest of the body. There are skeletal muscle pumps surrounding the blood vessels and are involved in bring the blood back to the heart. Since the A.V. valve is open, the blood can just basically flow back into the ventricles. Then when the atria contract, that gives the final “push” for the rest of the blood that enters the ventricles. Hope that helps.

  • I was having so much trouble understanding this concept until I watched your video. Completely understand it now and believe it is actually quite simple…but only after hearing/seeing you explain it. THANK YOU!!!

  • I was having so much trouble understanding this concept until I watched your video. Completely understand it now and believe it is actually quite simple…but only after hearing/seeing you explain it. THANK YOU!!!

  • @Elsabicton Leslie is no longer taking requests for specific videos, but he will definitely get to more systems in the future. He has many to work on at the moment. So stay tuned for more.

  • Leslie is no longer taking requests for specific videos, but he will definitely get to more systems in the future. He has many to work on at the moment. So stay tuned for more.

  • Leslie is no longer taking requests for specific videos, but he will definitely get to more systems in the future. He has many to work on at the moment. So stay tuned for more.

  • Our pleasure 🙂 Glad to know you find value in them. Please stay tuned. We have more Biology videos coming very soon!

  • Leslie,
    I came across your video when I was looking for a video on YouTube about the Cardiac Cycle. I am very fortunate to have clicked on your video! You are awesome. You lectures are very clear and easy to follow!!

  • @hnuvirn sure is right. it was really hard when I first started working out and my muscles were going nowhere at all. But I know why people are rushin to watch this video that definitely make you stronger with shaped muscles. i’ve heard legal action is already underway but you can get them for now from here > bit.ly/Ks5kBZ?=elnpyd

  • @hnuvirn sure is right. it was really hard when I first started working out and my muscles were going nowhere at all. But I know why people are rushin to watch this video that definitely make you stronger with shaped muscles. i’ve heard legal action is already underway but you can get them for now from here > bit.ly/Ks5kBZ?=elnpyd

  • @hnuvirn sure is right. it was really hard when I first started working out and my muscles were going nowhere at all. But I know why people are rushin to watch this video that definitely make you stronger with shaped muscles. i’ve heard legal action is already underway but you can get them for now from here > bit.ly/Ks5kBZ?=elnpyd

  • thank you so much for making it as fun.. its fun to understand it. Thank you so much!

  • these videos are perfect to watch as a review right before an exam since each video is short and packed with lots of information =]

  • You are seriously awesome. thank you so much for putting these videos up. They are life savers for college. very clear and informative!!

  • Awesome sir…u have made cardiac cycle video as simple n very informative. .Thanks a lot

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