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CONDUCTION OF CARDIAC IMPULSE CONDUCTION OF CARDIAC IMPULSE BY BY RERA_AVIS RERA_AVIS

Conduction of Cardiac Impulse

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Conduction of Cardiac Impulse

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Page 1: Conduction of Cardiac Impulse

CONDUCTION OF CARDIAC IMPULSECONDUCTION OF CARDIAC IMPULSE

BYBY

RERA_AVISRERA_AVIS

Page 2: Conduction of Cardiac Impulse
Page 3: Conduction of Cardiac Impulse

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.

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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

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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.

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NNH

AN

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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.

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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.

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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

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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

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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

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CONDUCTION VELOCITIES OF DIFFERENT PARTSCONDUCTION VELOCITIES OF DIFFERENT PARTS

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THANK YOUTHANK YOU