 |
The Sino-Atrial
Node
The heart's normal or intrinsic pacemaker is
called the sino-atrial node. It is located in the
upper right chamber (right atrium). A signal or
impulse is emitted to trigger the heart beat. The normal
heart beat is 60-100 beats per minute. At
times the heart may be slower, such as during
sleep, or faster as during activity or stress.
This impulse travels across the upper chambers of
the heart. However, in order to trigger the
pumping or lower chambers (the ventricles) the
impulse must cross the specialized electrical
(conduction) system. This connection between the
upper and lower chambers of the heart is in a
central area called the septum. Here a series of
specialized tissues take the impulse from the top
chamber, slow its progression down a bit, and then
pass it on to specialized fibers that transmit the
impulse across the pumping chambers to signal the
muscles within these chambers to contract and
pump. With the next heart beat, the process starts
again.
|
Arrhythmic
Disturbances
An arrhythmia may occur when any
portion of this sequence is interrupted or disturbed.
Among arrhythmic disturbances are the failure of the
pacemaker or electrical system to trigger appropriately
and conduct impulses properly. Other arrhythmias occur
when abnormal foci within the heart interrupt the normal
sequence of electrical stimulation and temporarily, or for
prolonged periods of time, initiate the electrical
sequence.
Arrhythmias may be benign, symptomatic,
life threatening or even fatal. Their consequences depend
not only on their manifestation but on the presence of
important abnormal structural conditions of the heart.
If you have any questions or concerns about this
site,
please contact webmaster@docnet.org.
|
