Properties of Cardiac Muscle Download

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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 than 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