,NURS 5337 Module 5 EKG Quiz | (2026) Q&A | University
of Texas at Arlington
1. On a standard 12-lead ECG, which wave represents atrial depolarization?
A) QRS complex
B) T wave
C) P wave
D) U wave
Correct Answer: P wave
Rationale: The P wave represents atrial depolarization, which leads to atrial contraction.
The QRS complex represents ventricular depolarization, the T wave represents ventricular
repolarization, and the U wave is a small deflection sometimes seen after the T wave.
Understanding these basic waveform components is essential for rhythm interpretation.
2. What is the primary function of the atrioventricular (AV) node in the cardiac conduction
system?
A) To initiate the electrical impulse that triggers each heartbeat
B) To delay the electrical signal before it reaches the ventricles
C) To transmit the impulse rapidly through the ventricular myocardium
D) To serve as the backup pacemaker if the sinoatrial node fails
Correct Answer: To delay the electrical signal before it reaches the ventricles
Rationale: The AV node delays the electrical impulse for approximately 0.12 to 0.20
seconds, allowing the atria to contract and fill the ventricles before ventricular contraction
,begins. The SA node initiates the heartbeat, the Purkinje fibers rapidly transmit the
impulse, and the AV junction can serve as a backup pacemaker.
3. A patient care technician is preparing to perform a 12-lead EKG for a patient who has a
heart rate of 225/min. Which paper-speed setting should the technician expect the
provider to prescribe?
A) 25 mm/sec
B) 50 mm/sec
C) 10 mm/sec
D) 100 mm/sec
Correct Answer: 50 mm/sec
Rationale: A paper speed of 50 mm/sec is used when the heart rate is extremely rapid, as
it spreads the complexes further apart on the paper, making them easier to visualize and
interpret. The standard paper speed is 25 mm/sec. Speeds of 10 mm/sec and 100 mm/sec
are not standard clinical settings.
4. Which structure of the cardiac conduction system is considered the primary pacemaker
of the heart?
A) Atrioventricular node
B) Bundle of His
C) Sinoatrial node
D) Purkinje fibers
Correct Answer: Sinoatrial node
Rationale: The sinoatrial (SA) node, located in the right atrial wall, is the primary
pacemaker of the heart, initiating electrical impulses at a rate of 60 to 100 beats per
, minute. The AV node, Bundle of His, and Purkinje fibers are downstream components that
can serve as backup pacemakers at slower rates.
5. What does the PR interval represent on an ECG tracing?
A) The time required for ventricular depolarization and repolarization
B) The time from the start of atrial depolarization to the start of ventricular depolarization
C) The time required for the ventricles to repolarize
D) The time from the end of the QRS complex to the start of the T wave
Correct Answer: The time from the start of atrial depolarization to the start of
ventricular depolarization
Rationale: The PR interval is measured from the beginning of the P wave to the
beginning of the QRS complex. It represents the time it takes for the electrical impulse to
travel from the SA node through the atria and AV node to the ventricles. A normal PR
interval is 0.12 to 0.20 seconds.
6. A PR interval that exceeds 0.20 seconds (more than five small boxes) indicates which
condition?
A) First-degree AV block
B) Second-degree AV block Type I
C) Third-degree AV block
D) Wolff-Parkinson-White syndrome
Correct Answer: First-degree AV block
Rationale: A PR interval longer than 0.20 seconds indicates first-degree AV block, which
is a delay in conduction through the AV node. Second-degree AV blocks involve dropped
of Texas at Arlington
1. On a standard 12-lead ECG, which wave represents atrial depolarization?
A) QRS complex
B) T wave
C) P wave
D) U wave
Correct Answer: P wave
Rationale: The P wave represents atrial depolarization, which leads to atrial contraction.
The QRS complex represents ventricular depolarization, the T wave represents ventricular
repolarization, and the U wave is a small deflection sometimes seen after the T wave.
Understanding these basic waveform components is essential for rhythm interpretation.
2. What is the primary function of the atrioventricular (AV) node in the cardiac conduction
system?
A) To initiate the electrical impulse that triggers each heartbeat
B) To delay the electrical signal before it reaches the ventricles
C) To transmit the impulse rapidly through the ventricular myocardium
D) To serve as the backup pacemaker if the sinoatrial node fails
Correct Answer: To delay the electrical signal before it reaches the ventricles
Rationale: The AV node delays the electrical impulse for approximately 0.12 to 0.20
seconds, allowing the atria to contract and fill the ventricles before ventricular contraction
,begins. The SA node initiates the heartbeat, the Purkinje fibers rapidly transmit the
impulse, and the AV junction can serve as a backup pacemaker.
3. A patient care technician is preparing to perform a 12-lead EKG for a patient who has a
heart rate of 225/min. Which paper-speed setting should the technician expect the
provider to prescribe?
A) 25 mm/sec
B) 50 mm/sec
C) 10 mm/sec
D) 100 mm/sec
Correct Answer: 50 mm/sec
Rationale: A paper speed of 50 mm/sec is used when the heart rate is extremely rapid, as
it spreads the complexes further apart on the paper, making them easier to visualize and
interpret. The standard paper speed is 25 mm/sec. Speeds of 10 mm/sec and 100 mm/sec
are not standard clinical settings.
4. Which structure of the cardiac conduction system is considered the primary pacemaker
of the heart?
A) Atrioventricular node
B) Bundle of His
C) Sinoatrial node
D) Purkinje fibers
Correct Answer: Sinoatrial node
Rationale: The sinoatrial (SA) node, located in the right atrial wall, is the primary
pacemaker of the heart, initiating electrical impulses at a rate of 60 to 100 beats per
, minute. The AV node, Bundle of His, and Purkinje fibers are downstream components that
can serve as backup pacemakers at slower rates.
5. What does the PR interval represent on an ECG tracing?
A) The time required for ventricular depolarization and repolarization
B) The time from the start of atrial depolarization to the start of ventricular depolarization
C) The time required for the ventricles to repolarize
D) The time from the end of the QRS complex to the start of the T wave
Correct Answer: The time from the start of atrial depolarization to the start of
ventricular depolarization
Rationale: The PR interval is measured from the beginning of the P wave to the
beginning of the QRS complex. It represents the time it takes for the electrical impulse to
travel from the SA node through the atria and AV node to the ventricles. A normal PR
interval is 0.12 to 0.20 seconds.
6. A PR interval that exceeds 0.20 seconds (more than five small boxes) indicates which
condition?
A) First-degree AV block
B) Second-degree AV block Type I
C) Third-degree AV block
D) Wolff-Parkinson-White syndrome
Correct Answer: First-degree AV block
Rationale: A PR interval longer than 0.20 seconds indicates first-degree AV block, which
is a delay in conduction through the AV node. Second-degree AV blocks involve dropped
