Video Transcript
What is the primary function of the
sinoatrial node, SAN? (A) Initiating the electrical
impulse that generates a heartbeat. (B) Passing electrical impulses
through the walls of the ventricles. (C) Initiating blood flow through
the veins of the heart. Or (D) encouraging division and
replication of heart cells.
This question asks about the
function of the sinoatrial node. So, what is the sinoatrial node,
where is it located, and how does it work? The sinoatrial node is part of the
electrical conduction system of the heart. This system is responsible for
regulating the heartbeat through regular electrical signals. You might recall the heart has four
chambers, two atria and two ventricles. The sinoatrial node is a small
cluster of specialized cardiac muscle cells and nerve cells, embedded in the wall of
the upper right chamber of the heart, or the right atrium.
The sinoatrial node is called the
pacemaker of the heart. This is because the signals that
travel through the heart and cause it to beat are generated here. At regular intervals, the
sinoatrial node generates an electrical impulse. This impulse moves through the
right atrium and is received by another node called the atrioventricular node. The signal is then passed on and is
finally propagated to the walls of the ventricles, through tiny fibers called
Purkinje fibers. This signal is what stimulates the
ventricles to contract, pumping blood out of the heart.
Now that we know more about the
sinoatrial node, we can eliminate some of our answer choices. First, we can eliminate answer
(D). We know that the sinoatrial node is
involved in the heart’s electrical conduction system and does not play a role in
cell division. In addition, we can eliminate
answer (C), because the sinoatrial node does not initiate the blood flow
specifically in the heart’s veins.
Now, let’s take a look at answer
(B), passing an electrical impulse through the walls of the ventricles. This answer describes the function
of another element of the heart’s electrical conduction system, the Purkinje
fibers. So the correct answer is (A). The primary function of the
sinoatrial node is initiating the electrical impulse that generates a heartbeat.
