Pacemaker Tissues of the Heart
Pacemaker produces impulses to trigger heartbeats.
Cells of the pacemaker tissue depolarize spontaneously â 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
â
Sets the pace of the heart
â
As SA node is the fastest among all
â
Normally the pacemaker of heart is SA node
â
SA node is called primary pacemaker of the heart
â
If SA node does not function properly
â
The next fastest tissue i.e. AV node becomes the pacemaker
â
AV node is called secondary pacemaker of the heart
â
If AV node also fails
â
Purkinje fibers set the pace
â
Purkinje fibers are called tertiary pacemaker
â
However Purkinje fibers are very slow and not reliable as pacemaker
â
Might need to implant artificial pacemaker
Comments