Basics Pacemaker Cells

• Myogenicity:

  • skeletal muscle is neurogenic, so contracts in response to an action potential which is generated in the neurological system
  • cardiac muscle is myogenic, so contracts in response to an action potentials which is generated in the myocardium
  • myogenic is aka auto-rhythmicity = inherent ability to spontaneously depolarise and create action potentials -> contraction
• • there are 2 main pacemaker tissues:
  • sinoatrial node is the prime pacemaker region
  • atrioventricular node is the secondary pacemaker region
  • these nodes are specialised collections of cells - modified myocytes
  • these nodes have unstable resting membrane potentials, so therefore are capable of producing action potentials without external input
  • once generated, action potentials will be conducted throughout the heart at a rate set by the rate of production of action potentials at the sinoatrial node

  A) sinoatrial node

  B) atrioventricular node

  
• • the sinoatrial node sits in the right superior aspect of the right atrium, just below the entrance point of the superior vena cava
  • the sinoatrial node is the prime pacemaker, because it is the best at generating action potentials, as it can produce action potentials at higher rate
  • the atrioventricular node is in the inferior medial aspect of the right atrium, just above the tricuspid/right atrioventricular valve
  • in health the atrioventricular node plays more of a role in conducting action potentials form the sinoatrial node, rather than producing action potentials