a. Name the elements of the intrinsic conduction system of the heart in order, beginning with the pacemaker. b. What is the important function of this conduction system?

Video transcript

Hi, everybody. Let's look at our next problem. It says, identify the correct order of the parts of the conduction system of the heart. And we've got four different answer choices with the same uh parts but listed in different orders. So I'm just gonna read off or I'm just going to read off the first one and then we'll determine which order is correct and then match that to our answer choice rather than reading four different times the same names. So our parts are as in choice a, the S A node or pacemaker, the A V bundle A V node, right and left bundle branches and Perini fibers. So let's think about the order in which these things go. And a little diagram of the heart can be helpful for this. I'm gonna draw actually a rough heart shape divided into our four quadrants just to help us keep us oriented. So labeled R A and RV, for right atrium and right ventricle. And then, excuse me, L A and LV, the left atrium and left ventricle. And let's think about where our electrical signal is going. So we start with the S A node or that pacemaker where it originates and that's up in the right atrium. The electoral signal then travels to the A V node, which as that name indicates is they are sort of at the center between all these areas between the atria and the ventricles. So that is the A V node. So, so far, we have in order S A node going to a V note, now we're going to travel along fibers to propagate that electrical signal throughout the heart. So immediately below that, a V node, we have what's usually called the bundle of hiss. That's not an option here. But we do have something called the A V bundle, which would make sense since it's again between the atria and ventricles. So we'll say that to match with our answer choices, we'll say that the A V bundle is next in our list. And then from there, it's going to start to split off to right and left sides as the fibers run down through the ventricles off to either side. And that would be the right and left bundle branches. And then finally, those fibers will turn up and run up along the ventricle walls to spread that electrical signal up throughout both ventricles. And those on either side will be the Perini fibers. So for our last two components here from the A V bundle, we go to the right and left bundle branches and then finally to the Perini fibers. So we have our correct order here. Let's go along here and look for the matching answer. So we start with the essay node. All of our answer choices have essay node first and we should next have the A V node. So only choice B and choice D have the A V node second. So we can go ahead and eliminate A and C after the A V node, we go to the A V bundle or the bundle of his that's correctly listed in both the choice is B and D. And then we break off into the right and left bundle branches which is correct in choice B but it is not correct in choice D which has Perini fibers next. So we can eliminate choice D and we have our answer here which is choice B and we can confirm that after right and left bundle branches, it correctly ends up with the peri fibers. So again, the correct order of the parts of the conduction system of the heart is choice B. The essay node followed by the A V node, then the A V bundle, the right and left bundle branches and the Perini fibers. See you in the next video.