Question

Which of the following is true regarding the conduction of electrical activity in the heart?

Select one:

a. Conduction through the AV node is relatively slow

b. The wave of depolarization travels directly from the atrial muscle to the ventricular muscle

c. The AV node determines heart rate in a healthy person

d. 2 of the above are correct

e. None of the above are correct

Answer 1

The answer is option a. Conduction through the AV node is relatively slow.
     
AV node conduction is relatively slow compared to the SA node because the nodal myocyte diameter is smaller and the myocytes in AV node is separated by connective tissue which also contribute to decrease in conduction velocity. This natural slowdown of conduction in AV node helps in completion of ventricular filling of blood from atria before ventricular contraction.

The wave of depolarization doesn't travels directly from the atrial muscle to the ventricular muscle. The wave depolarization travels by a conduction system which starts from the SA node to Internodal fibers which transmits the wave to atrial muscles and causes atrial contraction. Then it reaches the AV node and it transmits the wave to bundle of his, then to purkinje fibers which result in ventricular muscle contraction.

The AV node doesn't determines heart rate in a healthy person. SA node is known as the pacemaker of heart which determine the heart rate in a healthy person. When the SA node activity is affected by any cardiovascular diseases, the AV node take over the pacemaker function. But the AV node pacemaker activity is abnormal and should be given immediate medical care.