Conducting System and Nerve Supply of Heart

 Conducting System and Nerve Supply of Heart

by physiogyan 

What are the components of conducting system of the heart?

Conducting system of heart is meant for initiating and maintaining cardiac rhythm and establish proper co-ordination between the atrial and ventricular contactions. It is made up of specialized cardiac muscle fibers having a high degree of sensitivity and autorhythmicity.

Components of conducting system

Sinuatrial node (SA node)

Is also known as pacemaker.

Initiates the cardiac impulse.

Is located in the upper part of crista terminalis by the side of the opening of superior vena cava.

Impulse from SA node to AV node is carried by intermodal fibers.



Atrioventricular node (AV node )

Is situated in the right atrium , in the lower part of interatrial
septum.

It lies in the triangle of Koch, which is bounded by:

Base of septal cusp of tricuspid valve

Orifice of coronary sinus

Tendon of Todaro

 Atrioventricular bundle of HIS

From the AV node it descends in the interventricular septum and divides into:

Right ventricular branch

Left ventricular branch

The two branches descend in the interventricular septum and spread out in the walls of the respective ventricles to end as Purkinje fibers.

Describe briefly the nerve supply of heart.

The heart rate and the cardiac output are controlled by autonomic nervous system.

Sympathetic fibers are provided by the cardiac branches of superior, middle and inferior cervical ganglia (  preganglionic fibers reach from T2-T5 spinal segments).

Parasympathetic fibers are provided by the cardiac branches (superior, inferior and recurrent) of the left & right vagus nerves.

The sympathetic and parasympathetic fibers reach heart via the superficial and deep cardiac plexuses.
Superficial cardiac plexus is located below the arch of aorta. it is formed by:

Cardiac branch of superior cervical ganglion of left sympathetic chain.

Inferior cervical cardiac branch of left vagus.

Deep cardiac plexus is located behind the arch of aorta and in front of tracheal bifurcation. It is formed by:

Cardiac branches of middle and inferior cervical ganglion of both the sympathetic chain and from the superior cervical ganglion of right sympathetic chain.

Cardiac branches of T2-T5 ganglion of both the sympathetic chain.

Superior and recurrent branches of both the vagi and inferior cardiac branch of right vagus.

 

Physiogyan | | Tags: physiogyan