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Difficulty: MediumHuman Anatomy and Body Systems

During each heartbeat, a coordinated wave of electrical excitation travels through specialized cardiac tissue to trigger myocardial contraction. In what sequential order does this electrical impulse travel through the heart's conduction system from its origin to ventricular activation?

  1. 1Sinoatrial (SA) node generates an electrical impulse across the atrial walls.
  2. 2Atrioventricular (AV) node receives the impulse and briefly delays signal transmission.
  3. 3Atrioventricular bundle (Bundle of His) conducts the impulse down the interventricular septum.
  4. 4Purkinje fibers disperse the impulse throughout the ventricular myocardium.

Answer

Sinoatrial (SA) node → Atrioventricular (AV) node → Atrioventricular bundle (Bundle of His) → Purkinje fibers
The intrinsic electrical conduction of the heart begins at the sinoatrial (SA) node (the pacemaker in the right atrium), travels to the atrioventricular (AV) node (which introduces a brief delay), passes through the atrioventricular bundle (Bundle of His) within the septum, and finally spreads through the Purkinje fibers to activate the ventricular myocardium.

Step-by-Step Solution

1
Identify the origin site of the cardiac electrical signal.
The sinoatrial (SA) node in the superior wall of the right atrium initiates the action potential.
The SA node possesses the highest intrinsic rate of autorhythmicity and functions as the primary pacemaker.
2
Identify the relay station that receives the atrial excitation.
The atrioventricular (AV) node in the interatrial septum receives the impulse and delays it briefly.
The delay allows atrial systole to complete and ventricles to fill with blood before ventricular systole begins.
3
Trace the pathway conducting the signal through the interventricular septum.
The atrioventricular bundle (Bundle of His) and its bundle branches carry the signal inferiorly through the septum.
This tract provides the only electrical connection through the non-conductive fibrous skeleton separating atria and ventricles.
4
Determine the terminal distribution network stimulating ventricular contraction.
Purkinje fibers distribute the depolarizing wave throughout the ventricular myocardium.
Purkinje fibers have large diameters that facilitate rapid conduction, ensuring simultaneous, coordinated ventricular contraction from the apex upward.

Key Concept

Cardiac Conduction System Pathway
Estimated Time:1m 0s
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Topics

Human Anatomy and Body Systems

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