Officially the sino-atrial (SA) node sets the rhythmic pace of the heart. The impulse from the SA node that signals the atria to contract is slightly slowed down at the AV node. The effect of this delay is that the ventricles receive the impulse to contract a split second later and so the heart can function as its supposed to. Without that split second delay all four chambers would be contracting nearly simultaneously, and the heart would not be able to function efficiently.
Also included are the AV bundle, and Purkinje fibers. These are made up of modified cardiac muscle.
AV bundle originates in AV node, extends by two branches down the two sides of the interventricular septum, and continues as Purkinje fibers. Purkinje fibers extend out to papillary muscles and lateral walls of ventricles. The nerve supply consists of sympathetic nerves-accelerator nerves and
Vagus fibers-inhibitory, or depressor, nerves.
There are a specialized group of cells in the heart called the AV node. These cells fire to keep the heart beating regularly.
The heart is composed of it own specail kind of muscle. IE cardiac muscle
The contraction is controlled by nodal cells which are unique in the body.
calcium
The central nervous system supplies the body and muscle contraction. Striated muscle (skeletal muscle) contract voluntary with exception of the heart which is striated involuntary smooth muscle.
heart
The heart.
fibrillation
the lungs and the legs contract the heart for regular pulse that murmurs
Arrhthmyia of the heart, problems with smooth and skeletal muscle contractions; hyperkalemia can even stop the heart muscle.
The heart? /shrugs
the heart, it controls itself.
Basic muscle summation -an increase in the frequency with which a muscle is stimulated increases the strength of contraction. With increased stimuli to the heart if summation occurred the contractions would keep increasing.
cardiotonics increase the strenght of the muscle contractions that pump blood from the heart.
The heart you idiot!
the cardiac muscle is your heart. you tell me. ever heard of cardiac arrest? its also called a heart attack.