The conducting system of the heart

• Does heart generate its own impulses?


  Heart generates its own electrical impulses and beat independently of nervous or hormonal control
• Heart is supplied with what type of nerve fibers?

  sympathetic and parasympathetic nerve fibers.
• What do sympathetic and parasympathetic nerve fibers do?

  increase and decrease respectively the intrinsic heart rate
• Heart responds to number of circulating hormones. Examples?

  Adrenaline, thyroxine
• What initiate and conduct impulses?

  small group of specialized neuromuscular cells in the myocardium
• The conducting system of the heart consists of?


  SA node (Sinoatrial node)

  AV node (atrioventricular node)

  Atrioventricular bundle (bundle of his), bundle branches and purkinje fibers
• What is SA node?

  small mass of specialized cells
• What is the location of the SA node?

  It lies in the myocardium of the right atrium near the opening of the superior vena cava
• What is originate in the SA node?

  Stimulus for contraction of the heart
• Why is the SA node is called as pace maker?


  SA node initiates the heart beat and sets the rhythm of the heart beat
• What are the reasons for heart rate variations?

  Stimulation from the autonomic nervous system

  hormones such as adrenaline and thyroxine

  temperature
• What is AV node?

  Small of specialized cells
• Where is the AV node is situated?

  Wall of atrial septum which is located between the left and right atria
• What is the function of the AV node?

  Transmits the electrical signals from the atria into the ventricles
• What is AV bundle?

  A mass of specialized fibers
• From what the AV bundle is originated from?

  From the AV node
• What are purkinje fibers? 


  The AV bundle crosses the fibrous rings that separate atria and ventricle at the upper end of the ventricular septum. it divides into right and left bundle branches. Within the ventricular myocardium the branches break up into fine fibers. these fine fibers are called purkinje fibers
• AV bundle branches and the purkinje fibers function?


  Transmit electrical impulse from the AV node to the apex of the myocardium
• What happens as a result of electrical impulse transmit from AV bundle branches and purkinje fibers?

  Wave of ventricular contraction begins
• How blood is pumped to the pulmonary artery and aorta?


  The contraction sweeps upwards and outwards pumping blood simultaneously into the pulmonary artery and aorta