0:00
So this one's a tricky question.
00:02
The impulse, we're looking for the impulse that causes cardiac muscle, so that's muscle in your heart, cardiac muscle to contract is delivered to, and this, i'll underline that, because i think that's going to come into play, delivered to the ventricles, which are the bottom two chambers of the heart, by v, and then you have basically a fill in the blank.
00:48
Okay, so we're looking for the impulse that causes the cardiac muscle to contract and who delivers it.
00:56
We're not looking for the impulse, we're looking for what structure delivers the impulse to the ventricles.
01:01
So we have a few options.
01:03
We have a, the atrioventricular, so i'll abbreviate that as av, abbreviate it, so av bundle, atrioventricular bundle, and then they're saying that's the same as the bundle of his.
01:23
Then they have the sinoatrial node, the sa node, so i'll abbreviate that as well as sa node.
01:33
Then they have c, the purkinje fibers, and d, we have just the av node, a1, atrioventricular node, and finally, e, the medulla oblongata.
01:59
So thinking about how the contractions are started can help us eliminate some options here.
02:07
So remember that the heart has a built -in pacemaker, the sa node, right? so while the brain can influence the heart, certainly when we're talking about the ventricles, which remember ventricular contraction comes after, so i'm actually gonna write that down.
02:25
Ventricular contraction comes after atrial contraction.
02:45
So the way that that, you know, i could rephrase this as the atria contract first followed by the ventricles.
02:50
So if the ventricles are the second thing contracting, right, we can definitely eliminate the brain.
02:57
So i'm going to cross that off as the wrong answer, the medulla oblongata is part of the brain.
03:03
We know that there's a pacemaker, internal pacemaker of the heart, the sa node, and we know that the ventricles are the second thing to contract.
03:12
So it's definitely not gonna be the brain...