Conduction System Of Heart

• Conducting system of the heart

  Specialized cardiac muscle fibers responsible for initiation and conduction of cardiac impulse
• Components of the conducting system of the heart

  • Sinoatrial node
  • Atrial ventricular node
  • Atrioventricular bundle
  • Right and left branches of bundle of his
  • Sub endocardial Purkinje fibers
• Sinoatrial node


  Also known as node of Keith black, a small horseshoe shaped mass of specialized myocardial fibers situated in the wall of the right atrium, generates impulses about 70 per minute and initiates the contraction of cardiac muscle producing a heartbeat
• Atrial ventricular node


  Also known as node of taurah, smaller than the SA node, 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, conducts the cardiac impulse to the ventricle by the atrioventricular bundle, capable of generating impulses at a rate of about 60 per minute
• Atrioventricular bundle


  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
• Conduction of cardiac impulse

  1. Sinoatrial node generates impulses

  2. Impulses spread to the muscles of the atria making them contract

  3. Atrial ventricular 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

  4. Papillary muscles contract first to tighten the chordae tendineae

  5. Contraction of the ventricular muscle occurs
• Right and left branches of bundle of his

  Right branch passes down to the right side of the interventricular septum and then becomes sub endocardial on the right side of the septum, 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


  Terminal branches of the right and left branches of the bundle of His, spread sub endocardial II over the septum and the rest of the ventricular wall
• 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
• The whole 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
• Cardiac arrhythmias


  Defect or damage of conducting system causes alteration in the rhythmic contraction of the ventricle
• 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 most common cause of defective conduction through AV bundle is atherosclerosis of coronary arteries which leads to diminished blood supply to the conducting system
• Tachycardia


  Rapid pulse
• Bradycardia


  Slow pulse
• Arrhythmia


  Regular pulse