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Contraction that squeezes blood towards the exit is more efficient than a simple squeeze from all directions. Although the ventricular stimulus originates from the AV node in the wall separating the atria and ventricles, the Bundle of His conducts the signal to the apex. Depolarization propagates through cardiac muscle very rapidly.
[1] [2] This means that all atrial cells can contract together, and then all ventricular cells. Different shapes of the cardiac action potential in various parts of the heart Rate dependence of the action potential is a fundamental property of cardiac cells and alterations can lead to severe cardiac diseases including cardiac arrhythmia and ...
Ventricular relaxation, or diastole, follows repolarization of the ventricles and is represented by the T wave of the ECG. It too is divided into two distinct phases and lasts approximately 430 ms. [1] During the early phase of ventricular diastole, as the ventricular muscle relaxes, pressure on the remaining blood within the ventricle begins ...
Ventricular systole is the contractions, following electrical stimulations, of the ventricular syncytium of cardiac muscle cells in the left and right ventricles. Contractions in the right ventricle provide pulmonary circulation by pulsing oxygen-depleted blood through the pulmonary valve then through the pulmonary arteries to the lungs.
It is a form of cardiac arrhythmia in which ectopic foci within either ventricular or atrial myocardium, or from finer branches of the electric transduction system, cause additional beats of the heart. Some medications may worsen the phenomenon. [citation needed] Ectopic beats are considered normal and are not indicative of cardiac pathology.
The AV node's normal intrinsic firing rate without stimulation (such as that from the SA node) is 40–60 times/minute. [13] This property is important because loss of the conduction system before the AV node should still result in pacing of the ventricles by the slower pacemaking ability of the AV node.
The Purkinje fibers, named for Jan Evangelista Purkyně, (English: / p ɜːr ˈ k ɪ n dʒ i / pur-KIN-jee; [1] Czech: [ˈpurkɪɲɛ] ⓘ; Purkinje tissue or subendocardial branches) are located in the inner ventricular walls of the heart, [2] just beneath the endocardium in a space called the subendocardium.
Unlike most atrio-ventricular accessory pathways which conduct electrical impulses at a relatively fixed speed, conduction through a Mahaim pathway varies according to how rapidly it is stimulated. More frequent stimulation leads to slower conduction, known as decremental conduction. [4]