Physiologists conducting research on the electrical properties of the heart measure action potential conduction velocity at 4 different points within normal cardiac tissue. The results, expressed in terms of speed of conduction (meters per second), are as follows:Point 1 - 0.05 m/sec
Point 2 - 0.3 m/sec
Point 3 - 1.1 m/sec
Point 4 - 2.2 m/secFrom the following list of locations, which most likely corresponds to the order of points 1-2-3-4 (AV = atrioventricular)?

Question

Physiologists conducting research on the electrical properties of the heart measure action potential conduction velocity at 4 different points within normal cardiac tissue.  The results, expressed in terms of speed of conduction (meters per second), are as follows:Point 1 - 0.05 m/sec
Point 2 - 0.3 m/sec
Point 3 - 1.1 m/sec
Point 4 - 2.2 m/secFrom the following list of locations, which most likely corresponds to the order of points 1-2-3-4 (AV = atrioventricular)?

Quizplus · Accepted Answer

11ec160b_3c8b_d11c_9249_d72bba5b76a0_MD0001_00 Cardiac impulses normally originate in the sinoatrial (SA) node. SA node depolarization delivers an electrical impulse to the surrounding atrial myocardium, which carries the action potential to the atrioventricular (AV) node at a rate of 1.1 m/sec. Speed of conduction in the AV node is the slowest (0.05 m/sec), and this delay allows the ventricles to completely fill with blood during diastole. From the AV node, the action potential enters the His-Purkinje system. Impulses travel the fastest through the Purkinje fibers (2.2 m/sec), which ensures that the ventricles contract in a bottom-up fashion (necessary for efficient propulsion of blood into the pulmonary artery and aorta). From the Purkinje fibers, the action potential is transmitted to the ventricular myocardium, where it travels at a rate of 0.3 m/sec. Points 1-2-3-4 are arranged in order of increasing conduction speed (not conduction time), as follows: Point 1 - AV node (0.05 m/sec) Point 2 - Ventricular muscle (0.3 m/sec) Point 3 - Atrial muscle (1.1 m/sec) Point 4 - Purkinje system (2.2 m/sec) Educational objective: The cardiac action potential conduction speed is slowest in the atrioventricular node and fastest in the Purkinje system. Conduction speed of the atrial muscle is faster than that of the ventricular muscle.

Physiologists Conducting Research on the Electrical Properties of the Heart