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Pacemaker Tissues of the Heart

  • Pacemaker produces impulses to trigger heartbeats.

  • Cells of the pacemaker tissue depolarize spontaneously → fire action potential at regular intervals. This firing rate is different for different pacemaker tissues.

  • Following tissues have pacemaker activity:

    • SA Node (Sinoatrial Node): Firing rate 70-80 /min

    • AV Node (Atrioventricular Node): Firing rate 40 /min

    • Purkinje Fibers: Firing rate 20 impulses/min

The fastest pacemaker tissue dominates the others

Sets the pace of the heart

As SA node is the fastest among all

Normally the pacemaker of heart is SA node

SA node is called primary pacemaker of the heart

If SA node does not function properly

The next fastest tissue i.e. AV node becomes the pacemaker

AV node is called secondary pacemaker of the heart

If AV node also fails

Purkinje fibers set the pace

Purkinje fibers are called tertiary pacemaker

However Purkinje fibers are very slow and not reliable as pacemaker

Might need to implant artificial pacemaker


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