Question

sometimes when atrial cells other than SA node trigger atrial contactions, atrial flutter or atrial fibrillation may occur. when tgese heart rhythms occur, the ventricles do not beat at the same rate as the atria . what part of the condition system prevents the ventricles from beating as fast as the atria and how does it occur?

Answer 1

AV node act as a primary electrical connection between atria and ventricals.They play a very important role in conduction system.it is the AV node which controls how fast signals should travel from the top of the heart to the bottom of the heart.When an atrial tachycardia occurs it is the AV node that act as a regulator which prevents the ventricles from contracting so fast that the cardiac output drops too low.AV node regulates conduction by involving the conduction velocity of the tissue within the node.When the electrical wave front from the atria reaches the AV node ,it slows down due to slower conduction velocity inside the node.As a result a small delay occurs between the time that the atria finish contracting and the ventricles start to contract.Another delaying property known as decremental conductionis used to describe tissue that conducts slower when it recieves signals faster.When the atria are affected by a tachycardia,the AV node will begin to block signals due to decremental conduction ,as seen in atrial fibrillation.The decremental properties of conduction through the AV node prevent signal from passing to the ventricles and prevents atrial fibrillation from being fatal.