hi let's talk about cardiac conduction in this video we'll discuss the locations
of the major components of the conductive system of the heart
so the cardiac conduction system consists of specialized cardiomyocytes
some people in their minds they think of these as as nerve fibers coursing through the heart but
they're just cardiac muscle cells and recall that cardiac muscle tissue is autorhythmic
some areas more autorhythmic than others and each area is going to have its own distinct rate
i'm not going to get into any depth of physiology here i just want to relate to you the anatomical
structures of where these cardiomyocytes are found so that you can visualize it as you do learn your
physiology so our story begins in the sa node or the pacemaker region of the heart that has
the highest rate uh or highest intrinsic rate of cells within the heart this sa node
is the region that the cardiac plexuses are going to work upon so that would be extrinsic
regulation of heart rate that sa node is found at the superior portion of the crista terminalis
just sub epicardially so it's the myocardium that is just deep to the epicardium along that
crista terminalis now when we're talking about sub epicardial we should probably mention that
the crista terminalis is the ridge on the inside there's a sulcus terminalis that corresponds to
that ridge on the outside so from this sa node depolarization will occur and that depolarization
will affect the av node the atrioventricular node is found at the nexus of the interatrial
and interventricular septa just adjacent to the opening of the coronary sinus
this is going to be the conduit between the myocardium superior to the fiber skeleton of
the heart and the myocardium inferior to the fibrous skeleton of the heart
depolarizations from there will affect the atrioventricular bundle which is at the superior
margin of the muscular uh interventricular septum that atrioventricular bundle often
times called the bundle of his branches into two bundle branches a right and a left bundle branch
which are conducted along the margins of the muscular septum of the interventricular septum
the lion's share of the right bundle branch so i don't necessarily agree with this it
goes through the septa marginal trabecula and then the remainder is conducted down through the septum
and around to the wall of the right ventricle the left bundle branch follows a rather more
parsimonious path around the left ventricular wall and these are going to branch into purkinje fibers
which will serve the myocardium of the ventricles now any interruption of this pathway can
lead to issues now in particular if we were to disrupt this region in here that
could lead to ventricular fibrillations or v-fib or if we were to take it out entirely
perhaps even cardiac arrest you should keep this region in mind when
you think about the anterior and posterior interventricular branches and their sources
whether that posterior interventricular branch comes from the lca for a left dominant heart
the rca a right dominant heart or a co-dominant heart involving both of these so here is
a closer view of the right atrium and we can see that sa node at the superior
rim of the crista terminalis we can also see the av node at the nexus of the interatrial septum and
the atrioventricular septum just adjacent to the opening of the coronary sinus so we've discussed
some of the major collections of specialized cardiomyocytes the sa node av node av bundle
right and left bundle branches and purkinje fibers this is your summary slide thank you for your time