Okay, so I said to you then, that we're going to have an electrical of,
an electrical activity, which will depolarize the
cells, and as we depolarize the cells.
Then you know that, in muscle,
after depolarization, it's followed by a contraction.
And then we will relax.
So, and before relaxation, we have to have a repolarization of
the cells.
So the electrical activity will always be before the contractual vents.
So what are our electrical activities?
They have to go in a unidirectional manner, because we want to have a.
Unidirectional contraction occurring, that is in the atria before the ventricles.
And this is coordinated by their electrical
conduction system, or by the specialized cardiac myocites,
which are called the pacemakers. In the heart, we have several pacemakers.
The first is the sinoatria pacemaker, or the SA node, and it is
located in the right atrium, towards the upper region of the right atrium.
This is a very fast pacemaker and it beats at about 60 to 100 beats per
minute. The second pacemaker resides
between, at the junction between the atria and the ventricle on the
right side, and that is shown here, and this is the atria.
ventricular, node, and that is the A, or AV node.
At the AV node, we will have a slight
pause in the, in the electrical activity that's occurring within
the atrium, and then, the AV node will fire, and
it fires at about 40 to 60 beats per minute.
What's unusual about this node, is that, everywhere else
across this junction, between the atrium and the ventricle.
The electrical activity cannot move from one
chamber, the upper chambers to the lower chambers.
But at the AV node, the electrical signal, now, will be
allowed to move from the atria then down to, to the ventricles.
So it's the gateway from the upper chamber to the lower chamber.
And it brings electrical activity into the lower chambers.