The sinoatrial node (SAN): The sinoatrial node is the heart's pacemaker. It is a small patch of tissue that sends out waves of electrical excitation at regular intervals to initiate contractions.
Purkyne tissue: Purkyne tissue is specially adapted muscle fibres that conduct the wave of excitation from the AVN down the septum to the ventricles.
The need for coordination
- Cardiac muscle- can initiate its own contractions- myogenic
- The muscles in the atria & ventricles have their own natural frequency of contraction
- Atria muscle tends to contract at a higher frequency than the ventricles
- Contractions of chambers need to be synchronised to prevent fibrillation
How the heartbeat starts
- At the top…