Where is the av node
Conduction system of the heart - Sinoatrial node, AV Node, Bundle of His, Purkinje fibers Animation
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conducting system of the heart
components the conducting system of the
heart is made up of specialized cardiac
muscle fibers and is responsible for
initiation and conduction of cardiac
impulse the conducting system of the
heart consists of the following five
components sinoatrial node atrial
ventricular node atrioventricular bundle
right and left branches of bundle of his
sub endocardial Purkinje fibers
sinoatrial node sinoatrial node is also
known as node of Keith black it is a
small horseshoe shaped mass having
specialized myocardial fibers situated
in the wall of the right atrium in the
upper part of sulcus terminalis just
below the opening of the superior vena
cava it is known as pacemaker of the
heart because it generates impulses
about 70 per minute and initiates the
contraction of cardiac muscle producing
a heartbeat atrial ventricular node is
also known as node of taurah it is
smaller than the SA node and is located
in the lower part of the atrial septum
just above the attachment of septal
cusps of the tricuspid valve or opening
of the coronary sinus it conducts the
cardiac impulse to the ventricle by the
atrioventricular bundle the AV node is
capable of generating impulses at a rate
of about 60 per minute the speed of
conduction of cardiac impulse which is
about 0.11 seconds provides sufficient
time to the atria to empty their blood
into the ventricle before ventricles
start contracting atrial ventricular
bundle it begins from the AV node
crosses the AV ring and runs along the
inferior part of the membranous part of
the interventricular septum where it
divides into the left and right branches
since the skeleton which is a fibrous
framework of the heart separates the
muscles of atria from the muscles of the
ventricles the bun
of his is the only means of conducting
impulses from the atria to the
ventricles right and left branches of
the bundle of his the right branch
passes down to the right side of the
interventricular septum and then becomes
sub endocardial on the right side of the
septum a large part of it continues in
the septum marginal true baculum to
reach the anterior papillary muscle and
anterior wall of the ventricle its
Purkinje fibers then spread out beneath
the endocardium the left branch descends
on the left side of the ventricular
septum divides into Purkinje fibers
which are distributed to the septum and
left ventricle Purkinje fibers they are
the terminal branches of the right and
left branches of the bundle of His and
spread sub endocardial II over the
septum and the rest of the ventricular
wall the conducting system and mode of
contraction of cardiac muscle is
summarized as follows the SA node a
spontaneous source of cardiac impulse
initiates an impulse which rapidly
spreads to the muscles of the atria
making them contract the AV node picks
up the cardiac impulse from atria and
conducts it through the atrioventricular
bundle and its branches to the papillary
muscles and the walls of the ventricles
the papillary muscles contract first to
tighten the chordae tendineae
and then the contraction of the
ventricular muscle occurs arterial
supply of the conducting system the hole
of the conducting system of the heart is
supplied by the right coronary artery
except a part of the left branch of the
AV bundle which is supplied by the left
coronary artery clinical correlation
conducting system defects the defect or
damage of conducting system causes
cardiac arrhythmias the SA node is the
spontaneous source of generation of
cardiac impulses the AV node picks up
these impulses from atria and sends them
to the ventricles through AV bundle the
only means through which impulses can
spread from the atria two ventricles
if the AV bundle fails to conduct normal
impulses
there is alteration and the rhythmic
contraction of the ventricle which is
known as irate Mia's if complete bundle
block occurs there is complete
dissociation in the rate of contraction
of atria and ventricles the commonest
cause of defective conduction through AV
bundle is a thorough sclerosis of
coronary arteries which leads to
diminished blood supply to the
conducting system an important point to
be noted here is that rapid pulse is
called tachycardia the slow pulse is
called bradycardia whereas a regular
pulse is called a wreath Mia
