What effect does the nervous system have on the heart rate?
A. Stimulation by parasympathetic nerves
causes the heart rate to slow down.
B. Stimulation by sympathetic nerves sets the
resting heart rate of the pacemaker cells in
the SA node.
C. Stimulation by sympathetic nerves causes
the pacemaker cells of the AV node to
depolarize more rapidly than the pacemaker
cells of the SA node.
D. Stimulation by either the sympathetic or
parasympathetic nerves causes pacemaker
cells in the SA node to depolarize more
slowly.
E. The nervous system does not directly
affect the heart rate.
A
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