nerve conduction pathway

• The Sino atrial wall (SAN) is a small patch of specialised cardiac muscle tissue located in the wall of the right atrium. This area acts as the pacemaker for the rest of the heart, determining how often it will beat.
• SAN cells are myogenic (always active)
• Part 1 of nerve conduction pathway,

  Excitation from SAN goes across atria. Atrial systole happens to fill V with blood. Contraction stopped spreading to V by thin layer of tissue-forms the fibrous skeleton of heart.

  So, excitation passes to V from Atrio ventricular node (AVN).

  There is delay at the AVN ,to allow time for V to fill before V systole occurs. From the AVN, connecting fibres from bundle of his carry excitation wave down through wall between the right and left V. Wave of excitation spreads up through walls of the V and transmitted thru purkinje fibres.
• In the nerve conduction pathway, the main contraction, called ventricular systole, starts at the bottom of the heart and spreads upwards, squeezing blood UP out from the ventricles into the aorta and pulmonary artery.
• The conduction of impulses through the heart generates electrical impulses, which can be detected at the surface of the body. A recording of these electrical changes that accompany each cardiac cycle or heartbeat is called an ECG or a electrocardiogram
• In a typical ECG, three clearly recognizable waves accompany each heartbeat.


  • P wave
  • QRS wave
  • T wave