Cardiac Muscle

• The cardiac muscle is what?

  Myogenic - it can contract and relax without receiving signals from nerves
• What controls the regular heartbeat?

  The pattern of contractions (contract and relax)
• Where does the process start?

  In the SAN
• What is the SAN?

  Sinoatrial node
• Where can the SAN be found?

  In the wall of the right atrium
• Describe the SAN?


  • Like a pacemaker- sets the RHYTHM of the heartbeat
• How does the SAN set the rhythm of the heartbeat?

  By sending out regular waves of electrical activity to the atrial walls

  • this causes the RIGHT AND LEFT ATRIA TO CONTRACT AT THE SAME TIME
• What does collagen tissue do?

  A BAND of NON-CONDUCTING COLLAGEN TISSUE prevents the waves of electrical activity from being passed directly from the atria to the ventricles

  Instead, these waves of electrical activity are transferred from the SAN --> AVN
• What is the AVN?

  Atrioventricular node
• What is the AVN responsible for?

  Passing the waves of electrical activity on to the bundle of His
• The AVN is responsible for what?

  Passing the waves of electrical activity on to the bundle of His

  BUT, there is a slight delay before the AVN reacts, to make sure the atria have emptied before the ventricles contract
• why is there a slight delay before the AVN reacts?

  To make sure the atria have emptied before the ventricles contract
• What is the bundle of His?


  A group of muscle fibres responsible for conducting the waves of electrical activity between the ventricles to the apex of the heart
• what is the apex of the heart?

  the bottom of the heart
• what does the bundle of His split into?

  Finer muscle fibres in the right and left ventricle walls, called the Purkyne tissue
• What does the Purkyne tissue do?

  Carries the waves of electrical activity into the muscular walls of the right and left ventricles, causing them to contract simultaneously, from the bottom up