>>Dr. Ketchum: The goal of this video is to
give you an overview of the autonomic innervation to the heart. Remember, this is just an overview.
I would like to start this video a little differently by asking you to pause the video
and then try to answer as many of these questions as you can, then restart the video to listen
to the explanation. Question one: What are the two branches of the autonomic nervous
system? We have been studying the brain for quite a while now, so you know that the autonomic
nervous system has two branches—the parasympathetic and sympathetic branches. Question two: What area of the brain controls the division of the autonomic nervous system dominating? This
is the cardiovascular control center; this center is located in the medulla oblongata.
Now let’s get down tot the specifics. In this diagram, I’ve color-coded the two different
branches of the autonomic nervous system to look at their innervation to the heart. So
we are going to begin with those in green. The green nerves are the sympathetic nerves.
Look closely at the diagram. Can you see the regions of the heart that are innervated by
these sympathetic nerves? The regions are the SA node, the AV node, and the ventricular
myocardium. Remember, the sympathetic nerves cause heart rate and force of contraction
to increase. Now let’s focus on the parasympathetic nerves; these nerves are shown in blue. Remember
that the specific parasympathetic nerve we are talking about is the Vagus nerve.
Look closely at the diagram; can you see the regions of the heart that are innervated by
these parasympathetic nerves? The regions are the SA node and the AV node, not the ventricular
myocardium. Remember, the parasympathetic nerves cause heart rate to decrease, but have
no effect on ventricular contractility.