Question 1

Which structure in the heart is responsible for initiating the electrical impulse that sets the pace for the heartbeat?

Accepted Answer

Sinoatrial (SA) node

Question 2

A patient’s ECG shows a prolonged PR interval of $$0.24$$ seconds. What is the most likely diagnosis?

Accepted Answer

First-degree heart block

Question 3

Which part of the ECG corresponds to ventricular depolarization?

Accepted Answer

QRS complex

Question 4

If the impulse is not generated in the SA node, which ECG interval is most likely to be reduced?

Accepted Answer

PR interval

Question 5

Which formula correctly calculates cardiac output?

Accepted Answer

$$CO = SV 	imes HR$$

Question 6

During which period can a second action potential NOT be generated in cardiac muscle, regardless of stimulus strength?

Accepted Answer

Absolute refractory period

Question 7

A patient’s ECG shows an elevated ST segment. What is the most likely clinical significance?

Accepted Answer

Myocardial infarction (heart attack)

Question 8

Which wave on the ECG represents the depolarization of the interventricular septum?

Accepted Answer

Q wave

Question 9

If a patient has no communication between the atria and ventricles, which type of heart block is present?

Accepted Answer

Third-degree heart block

Question 10

Which component of the heart’s conduction system directly stimulates the ventricular muscle cells to contract?

Accepted Answer

Purkinje fibers

Question 11

A prolonged QT interval on an ECG is associated with which clinical risk?

Accepted Answer

Increased risk of ventricular arrhythmias

Question 12

Which of the following best describes Starling’s Law of the heart?

Accepted Answer

The heart’s force of contraction increases as it is stretched by increased venous return

Question 13

Which ECG interval represents the time from the beginning of atrial depolarization to the beginning of ventricular depolarization?

Accepted Answer

PR interval

Question 14

If the left ventricle has more muscle and more Purkinje fibers, which ECG wave is most affected?

Accepted Answer

S wave

Question 15

Which of the following is the correct sequence of the heart conduction pathway?

Accepted Answer

SA node → Internodal pathways → AV node → Bundle of His → Branch bundles → Purkinje fibers

Question 16

During exercise, which change would you expect to see in the ECG tracing?

Accepted Answer

Increased heart rate and shorter R-R intervals

Question 17

Which standard limb lead records the electrical activity between the right arm and left leg?

Accepted Answer

Lead II

Question 18

What is the clinical significance of an enlarged R wave on an ECG?

Accepted Answer

Enlarged ventricles

Question 19

Which interval on the ECG represents the duration of the ventricular action potential?

Accepted Answer

QT interval

Question 20

A patient’s ECG shows a normal PR interval but a prolonged QT interval. What is the most likely risk associated with this finding?

Accepted Answer

Increased risk of ventricular arrhythmias

Conduction System of the Heart and Electrocardiography: Study Notes

Study Guide - Practice Questions