1. Properties of Cardiac Muscle Dr. Mahvash Khan MBBS, Mphil

2. Automaticity/Rhythmicity Automaticity means the ability of the cell to undergo depolarization spontaneously causing the production of electrical impulses Rhythmicity means that spontaneous depolarization occurs at regular intervals

3. Conductivity Conductivity is the ability to propagate an impulse. Normally impulses are conducted in one direction Conductivity may be increased or decreased under various circumstances

4. Contractility Cradiac muscle contracts in response to the electrical impulse generated by the SA node

5. Refractory Period The refractory period of the myocardial fibers is of much longer duration than that of skeletal muscle fibers and lasts approximately as long as the cardiac contraction

6. Excitability The heart muscle responds to stimuli which may be mechanical, electrical or chemical

7. All or None Law Heart is a functional syncytium therefore all its fibers act as a single fiber Heart either does not contract at all or it contracts with full force

8. Frank Starling Law of the Heart This law states that with in limits the force of ventricular contraction is directly proportional to the end-diastolic length of the cardiac muscle fibers which inturn is closely related to ventricular end-diastolic volume