MEANING. The conducting system of the heart consists of cardiac muscle cells and conducting fibers (not nervous tissue) that are specialized for initiating impulses and conducting them rapidly through the heart. It provides the heart its automatic rhythmic beat.  The purpose is to Generating  rhythmical electrical impulses to cause rhythmical contraction of the heart muscle. Conducting these impulses rapidly throughout the heart.       This pathway is made up of 5 elements: The sino-atrial (SA) node. The atrio-ventricular (AV) node. The bundle of His. The left and right bundle branches. The Purkinje fibers. SINOATRIAL NODE The sinoatrial (SA) node is a collection of specialized cells (pacemaker cells), and is located in the upper wall of the right atrium, at the junction where the superior vena cava enters. These pacemaker cells can spontaneously generate electrical impulses. The wave of excitation created by the SA node spreads via gap junctions across both atria, resulting in atrial contraction (atrial systole) – with blood moving from the atria into the ventricles. The SA node is supraventricular and is sensitive to parasympathetic and sympathetic influence. The SA node generates impulses and influenced by the Autonomic Nervous System: Sympathetic nervous system – increases firing rate of the SA node, and thus increases heart rate. Parasympathetic nervous system – decreases firing rate of the SA node, and thus decreases heart rate THE INTER NODAL PATHWAYS consist of three bands (anterior, middle, and posterior) that lead directly from the SA node to the next node in the conduction system, the atrioventricular node. The impulse takes approximately 50 m s (milliseconds) to travel between these two nodes. Bachmann's bundle (BB), also known as the interatrial bundle, myocardial strands connecting the right and left atrial walls and is considered to be the main pathway of interatrial conduction. THE AV NODEThe AV node is located in the posterior wall of the right atrium immediately behind the tricuspid valve. Cause of Slow Conduction in the A-V Node What is the significance of AV nodal delay? The cardiac impulse does not travel from the atria to the ventricles too rapidly. It is primarily the AV node and it’s adjacent fibers that delay this transmission into the ventricles     AV BUNDLE OR BUNDLE OF HIS From the AV node arises a special conducting pathway . RIGHT AND LEFT BUNDLE BRANCHES FASCICLE The right bundle branch contains one fascicle. The left bundle branch into three fascicles: The left anterior, The left posterior, and The left septal fascicle. PURKINJE FIBRES The LT and RT bundle branches divides in turn course sidewise around each ventricular chamber and back toward the base of heart. The ends of Purkinje fibers penetrate about one third of the way into muscle mass and finally become continuous with cardiac muscle fibers ,abundant with glycogen and extensive gap junctions, rapidly transmit cardiac action potentials in 0.03sec

1. CONDUCTIVE SYSTEM OF THE
HEART
PREPARED BY
MRS. WINCY THIRUMURUGAN

3. Meaning:
The conducting system of the heart consists
of cardiac muscle cells and conducting fibers
(not nervous tissue) that are specialized for
initiating impulses and conducting them
rapidly through the heart.
The conducting system provides the heart its
automatic rhythmic beat.

4. The heart has a special conduction system for the following
purpose
•Generating rhythmical electrical impulses to cause
rhythmical contraction of the heart muscle.
•Conducting these impulses rapidly throughout the
heart.
This pathway is made up of 5 elements:
•The sino-atrial (SA) node.
•The atrio-ventricular (AV) node.
•The bundle of His.
•The left and right bundle branches.
•The Purkinje fibres.

7. SINOATRIAL NODE
The sinoatrial (SA) node is a collection of specialised
cells (pacemaker cells), and is located in the upper wall
of the right atrium, at the junction where the superior
vena cava enters.
These pacemaker cells can spontaneously
generate electrical impulses. The wave of excitation
created by the SA node spreads via gap
junctions across both atria, resulting in atrial
contraction (atrial systole) – with blood moving from the
atria into the ventricles.

8.  The SA node is supraventricular and is sensitive
to parasympathetic and sympathetic influence.
The SA node generates impulses and influenced by
the Autonomic Nervous System:
•Sympathetic nervous system – increases
firing rate of the SA node, and thus increases
heart rate.
•Parasympathetic nervous system – decreases
firing rate of the SA node, and thus decreases

9. SA NODE

11. THE INTER NODAL PATHWAYS
The internodal pathways consist
of three bands (anterior, middle,
and posterior) that lead directly from
the SA node to the next node in the
conduction system, the
atrioventricular node. The impulse
takes approximately 50 ms
(milliseconds) to travel between
these two nodes.

12. Bachmann's bundle (BB),
also known as the interatrial
bundle, is well recognized as
a muscular bundle
comprising of parallel aligned
myocardial strands
connecting the right and left
atrial walls and is considered
to be the main pathway of
interatrial conduction.

13. THE AV NODE
The AV node is located in the posterior wall of the right
atrium immediately behind the tricuspid valve.
Cause of Slow Conduction in the A-V Node
The cause of slow conduction is mainly due to
reduced number of gap junctions between the
successive cells in the conducting pathways. Becauses of
this there is great resistance to conduction of excitatory
ions from one conducting fiber to the next.

14. What is the significance of AV nodal delay?
• The cardiac impulse does not travel from the atria to
the ventricles too rapidly.
• This delay allows time for the atria to empty their
blood into the ventricles before ventricular contraction
begins. This increases the efficiency of the pumping
action of the heart.
• It is primarily the AV node and it’s adjacent fibers that
delay this transmission into the ventricles

16. AV BUNDLE OR BUNDLE OF HIS
•From the AV node arises a special conducting pathway
named the bundle of His. Except for the very small part
which penetrates through the AV fibrous tissue and has low
conduction velocity.
•Normally the Bundle of His is the only conducting mass
between the atrial and ventricular musculature and it
transmits the cardiac impulses from the AV node to the
ventricles.
•The bundle of His is named after its discoverer, German
cardiologist Wilhelm His (1836–1934).

17. RIGHT AND LEFT BUNDLE BRANCHES
• After penetrating the fibrous tissue between the atrial and
ventricular muscle, the distal portion of the A-V bundle passes
downward in the ventricular septum for 5 to 15 mm toward the
apex of the heart.
•It descends down the membranous part of the interventricular
septum, before dividing into two main bundles:
Right bundle branch – conducts the impulse to the Purkinje
fibres of the right ventricle
Left bundle branch – conducts the impulse to the Purkinje
fibres of the left ventricle.

19. FASCICLE
Fascicle is a bundle of
structures, such as nerve or
muscle fibres or conducting
vessels .
• The right bundle branch
contains one fascicle.
• The left bundle branch into
three fascicles:
The left anterior,
 The left posterior, and
The left septal fascicle.

20. PURKINJE FIBRES
• The LT and RT bundle branches divides in turn course sidewise around each
ventricular chamber and back toward the base of heart.
• The ends of Purkinje fibers penetrate about one third of the way into muscle mass
and finally become continuous with cardiac muscle fibers
• The Purkinje fibres abundant with glycogen and have extensive gap junctions.
• These cells rapidly transmit cardiac action potentials from the atrioventricular
bundle to the myocardium of the ventricles.
• This rapid conduction allows coordinated ventricular contraction (ventricular
systole) and blood is moved from the right and left ventricles to the pulmonary
artery and aorta respectively.Clinic
• From the time the cardiac impulse enters the bundle branches until it reaches the
terminations of Purkinje fibers , the total time averages only 0.03 sec

22. ONE- WAY CONDUCTION THROUGH AV
BUNDLE
A special characteristic of the A-V bundle is
it’s inability, except in the abnormal states
, of action potentials to travel backward
from the ventricles to the atria.
•It will prevents re-entry of cardiac impulse
by this route from the ventricles to the
atria.

24. An artificial pacemaker
It is a small electronic device
commonly fitted to monitor and correct
heart rate and rhythm.
It is inserted into the chest under the
left clavicle, with wires connected to
the heart via the venous system.
The most common indication for a
pacemaker is bradycardia. Once
inserted, the pacemaker monitors the
heart rate, and only fires if the rate
becomes too slow.
Pacemakers can also be used to treat
some tachycardias, heart block and
other rhythm abnormalities.