Atrioventricular Node
The 
atrioventricular node, or AV node,
is made up of
another cluster of specialized cardiac conduction system cells.
The AV node forms a pathway for impulse conduction that bridges
between the atria and ventricles. Depolarization of the AV node
is relatively slow due to the intrinsic characteristics of its
cells. This causes a delay in the transmission of the
depolarization wave to the ventricles. The transmission of the
wave through the AV node is relatively weak, thus is considered
silent on the 
electrocardiogram.
atrioventricular node, or AV node,
is made up of
another cluster of specialized cardiac conduction system cells.
The AV node forms a pathway for impulse conduction that bridges
between the atria and ventricles. Depolarization of the AV node
is relatively slow due to the intrinsic characteristics of its
cells. This causes a delay in the transmission of the
depolarization wave to the ventricles. The transmission of the
wave through the AV node is relatively weak, thus is considered
silent on the 
electrocardiogram.