Cardiac Conduction Quiz: Nodes, Bundle Branches and Purkinje Fibers

Trace how an electrical impulse normally travels through the heart. Focus on where it starts, where conduction slows, and how ventricular activation spreads.

8 questions · Estimated 6–8 minutes. Select your answer mentally, then open the explanation to check your reasoning.

1. Which structure normally initiates the heartbeat in a healthy adult?

  1. AV node
  2. SA node
  3. Bundle of His
  4. Left bundle branch
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Answer: B. SA node

The sinoatrial (SA) node normally acts as the heart's primary pacemaker. It lies in the right atrial wall near the opening of the superior vena cava.

2. Which structure normally slows conduction between atrial and ventricular activation, allowing time for ventricular filling?

  1. Purkinje fibers
  2. Right bundle branch
  3. AV node
  4. Left bundle branch
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Answer: C. AV node

Slow conduction through the atrioventricular (AV) node creates a delay before ventricular activation. This allows atrial contraction to contribute to ventricular filling before ventricular systole.

3. After the bundle branches, which network rapidly distributes the impulse through the ventricular conduction system?

  1. SA node
  2. Pulmonary veins
  3. Chordae tendineae
  4. Purkinje fibers
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Answer: D. Purkinje fibers

Purkinje fibers rapidly distribute electrical impulses to ventricular myocardium. Chordae tendineae are fibrous cords that support AV valve leaflets; they are not part of the electrical conduction pathway.

4. In the normal conduction system, which structure carries the impulse from the AV node toward the bundle branches?

  1. Coronary sinus
  2. AV bundle (bundle of His)
  3. SA node
  4. Mitral annulus
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Answer: B. AV bundle (bundle of His)

The AV bundle, or bundle of His, carries the impulse from the AV node through the fibrous skeleton before dividing into bundle branches. It provides the normal electrical connection between atrial and ventricular myocardium.

5. On a normal ECG, the P wave represents which electrical event?

  1. Atrial depolarization
  2. Ventricular depolarization
  3. Ventricular repolarization
  4. AV valve closure
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Answer: A. Atrial depolarization

The P wave represents atrial depolarization. Atrial contraction follows this electrical activation. An ECG records electrical activity, so the wave is not a direct recording of valve motion or muscle contraction.

6. On a normal ECG, the QRS complex primarily represents:

  1. Atrial repolarization alone
  2. Ventricular repolarization
  3. Ventricular depolarization
  4. SA node recovery alone
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Answer: C. Ventricular depolarization

The QRS complex primarily represents ventricular depolarization. Atrial repolarization usually occurs during this interval but is obscured by the much larger ventricular electrical signal.

7. Which event produces the T wave on a normal ECG?

  1. Atrial depolarization
  2. Ventricular depolarization
  3. Aortic valve opening
  4. Ventricular repolarization
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Answer: D. Ventricular repolarization

The T wave represents ventricular repolarization, the electrical recovery of ventricular muscle cells. It should not be confused with the QRS complex, which represents their depolarization.

8. Increased parasympathetic input through the vagus nerve normally has which effect?

  1. Increases SA node firing and speeds AV conduction
  2. Slows SA node firing and AV nodal conduction
  3. Stops all Purkinje activity in a healthy heart
  4. Reverses the direction of ventricular conduction
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Answer: B. Slows SA node firing and AV nodal conduction

Vagal activity normally reduces SA node firing and slows conduction through the AV node. Sympathetic stimulation generally has the opposite effects. Normal vagal activity does not reverse the conduction pathway.

Further reading