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Muscle
types. Cardiac muscle
The
heart is the pump that keeps blood circulating throughout
the body and thereby transports nutrients, breakdown products,
antibodies, hormones, and gases to and from the tissues.
The heart consists mostly of muscle, the myocardial cells
(collectively termed the myocardium), arranged in ways that
set it apart from other types of muscle. The outstanding
characteristics of the action of the heart are its contractility,
which is the basis for its pumping action, and the rhythmicity
of the contraction.
Heart
muscle differs from its counterpart, skeletal muscle, in
that it exhibits rhythmic contractions. The amount of blood
pumped by the heart per minute (the cardiac output) varies
to meet the metabolic needs of the peripheral tissues (muscle,
kidney, brain, skin, liver, heart, gastrointestinal tract).
The cardiac output is determined by the contractile force
developed by the muscle cells of the heart (myocytes) as
well as the frequency at which they are activated (rhythmicity).
The factors affecting the frequency and force of heart muscle
contraction are critical in determining the normal pumping
performance of the heart and its response to changes in
demand.
