Properties of Cardiac Muscle Dr Mahvash Khan MBBS

Properties of Cardiac Muscle Dr. Mahvash Khan MBBS, Mphil

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

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

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

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

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

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

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