In electrocardiography, during a cardiac cycle, once an action potential is initiated, there is a period of time that a new action potential cannot be initiated. This is termed the effective refractory period (ERP) of the tissue. This period is also termed the absolute refractory period (ARP). During this period, depolarization on adjacent cardiac muscles does not produce a new depolarization in the current cell as it has to refract back to phase 4 of the action potential before a new action potential can activate it. ERP acts as a protective mechanism and keeps the heart rate in check and prevents arrhythmias and coordinates muscle contraction. Anti-arrhytmic agents used for arrhythmias usually prolong the ERP. For the treatment of Atrial fibrillation, it is a problem that the prolongation of the ERP by these agents also affects the ventricles, which can induce other types of arrhythmias.
-
myocardial action potential
|
Famous quotes containing the words effective and/or period:
“Justice in the hands of the powerful is merely a governing system like any other. Why call it justice? Let us rather call it injustice, but of a sly effective order, based entirely on cruel knowledge of the resistance of the weak, their capacity for pain, humiliation and misery. Injustice sustained at the exact degree of necessary tension to turn the cogs of the huge machine-for- the-making-of-rich-men, without bursting the boiler.”
—Georges Bernanos (18881948)
“Not only do our wives need support, but our children need our deep involvement in their lives. If this period [the early years] of primitive needs and primitive caretaking passes without us, it is lost forever. We can be involved in other ways, but never again on this profoundly intimate level.”
—Augustus Y. Napier (20th century)