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Conduction of Cardiac Impulse
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CONDUCTION OF CARDIAC IMPULSECONDUCTION OF CARDIAC IMPULSE
BYBY
RERA_AVISRERA_AVIS
TRANSMISSION OF IMPULSE FROM SA NODE TRANSMISSION OF IMPULSE FROM SA NODE TO ATRIA TO ATRIA
Impulse is transmitted directly to atrial muscle fibers of right atrium like ripples over pond.
Impulse is transmitted to left atrium through anterior interatrial band of bachmann.
TRANSMISSION OF IMPULSE FROM SA NODE TRANSMISSION OF IMPULSE FROM SA NODE TO AV NODETO AV NODE
Impulse is transmitted from SA node to AV node through 3 specialized conduction bundles
Anterior internodal bundle of Bachman
Middle internodal bundle of Wenckhebach
Posterior internodal bundle of Thorel
AV NODEAV NODE
AV node is located in the posterior wall of right atrium behind the opening of tricuspid valve.
It is also called as AV node of Tawara It is 22 mm long, 10mm wide and 3mm thick AV node has three portions
Atrionodal portion ( AN portion)
Nodal portion ( N portion)
Nodal His portion ( NH portion )
AV node continues with the common bundle of His
( AV bundle).
Cardiac impulse is delayed for 0.09 seconds in AV node because of reduced conduction velocity in the node mainly
in N and NH portions.
NNH
AN
COMMON BUNDLE OF HIS ( AV NODAL BUNDLE)COMMON BUNDLE OF HIS ( AV NODAL BUNDLE) Bundle of His has two portions
Proximal (penetrating) portion
Distal portion Further delay for 0.04 seconds occurs in the bundle of His
mainly in the proximal penetrating portion.
Thus a total delay of 0.13 seconds occur during transmission through AV node and proximal portion of bundle of His.
This delay occurs because of reduced number of gap junctions in this part of conduction system which increases the resistance
This delay allows atria to contract 0.16 seconds ahead of
ventricles. So that the blood present in atria is pushed in the ventricles before they start contracting.
TRANSMISSION THROUGH BUNDLE BRANCHESTRANSMISSION THROUGH BUNDLE BRANCHES
Common bundle of His after penetrating through the atrioventricular fibrous tissue (AV Septum) passes down in the interventricular septum for 5-15 mm and then divides in two branches
RIGHT BUNDLE BRANCH
LEFT ANTERIOR FASICLE
LEFT BUNDLE BRANCH
LEFT POSTERIOR FASICLE
Each of three bundles ( RBB,LAF,LPF) spread down towards the apex of heart and progressively divides in smaller branches.
These branches supply impulse to all parts of ventricular myocardium through specialized Purkinje fibers.
Conduction of cardiac impulse is very quick once it passes through the AV node and common bundle. Rapid transmission is due to very high permeability of gap junctions present in this part of conductive system
Purkinje fibers are broadest cells in the heart. Their diameter is 70 to 80 um and their conduction velocity is up to 4 m/sec
The ends of Purkinje fibers penetrate into the muscle fibers of ventricles and become continuous with them and then impulse continues from one muscle fiber to the other.
This transmission is slightly slow at a rate of 0.5m/s
ONE WAY TRANSMISSION OF IMPULSE IN AV ONE WAY TRANSMISSION OF IMPULSE IN AV NODE AND AV BUNDLENODE AND AV BUNDLE
INABILITY OF ACTION POTENTIALS TO TRAVEL BACKWORDS INTO ATRIA
TRANSMISSION OF IMPULSE FROM ATRIA TO VENTRICLES OCCURS THROUGH AV NODE ONLY
SPREAD OF IMPULSE IN VENTRICLESSPREAD OF IMPULSE IN VENTRICLES
First part to be activated is interventricular septum
Second is anteroseptal portion of ventricles
Third is bulky anterior and apical portion
Finally posterobasal portion
Transmission of impulse occurs from endocardiun to epicardium i.e. inside out
CONDUCTION VELOCITIES OF DIFFERENT PARTSCONDUCTION VELOCITIES OF DIFFERENT PARTS
THANK YOUTHANK YOU