Question 1

Which structure in the heart is primarily responsible for setting the pace of the heartbeat under normal physiological conditions?

Accepted Answer

Sinoatrial (SA) node

Question 2

During the cardiac cycle, what event immediately follows the closure of the atrioventricular (AV) valves?

Accepted Answer

Isovolumic ventricular contraction

Question 3

A patient’s ECG shows a prolonged P-R segment. What does this most likely indicate?

Accepted Answer

Delayed conduction through the AV node

Question 4

Which of the following best describes the QRS complex on an ECG?

Accepted Answer

Ventricular depolarization

Question 5

If the SA node fails, which structure can take over as the pacemaker, and at what approximate rate?

Accepted Answer

AV node at 50 bpm

Question 6

Which phase of the cardiac cycle is associated with the highest ventricular pressure?

Accepted Answer

Ventricular ejection

Question 7

Calculate the heart rate if the time between two consecutive R waves on an ECG is $0.8$ seconds. Use the formula $HR = \frac{60}{R-R\ interval\ (s)}$.

Accepted Answer

$HR = \frac{60}{0.8} = 75\ bpm$

Question 8

Which event is responsible for the 'dup' sound heard during the cardiac cycle?

Accepted Answer

Closure of the semilunar valves

Question 9

A patient’s ECG shows more P waves than QRS complexes. What is the most likely explanation?

Accepted Answer

Second-degree AV block

Question 10

Which of the following best explains why mechanical contraction of the heart lags behind the electrical events seen on the ECG?

Accepted Answer

Mechanical contraction is triggered by the action potential, which precedes contraction

Question 11

Which of the following is the correct sequence of electrical conduction through the heart?

Accepted Answer

SA node → AV node → Bundle of His → Purkinje fibers

Question 12

Which phase of the cardiac cycle is characterized by no change in ventricular volume but a rapid increase in pressure?

Accepted Answer

Isovolumic ventricular contraction

Question 13

What is the main physiological purpose of diastole in the cardiac cycle?

Accepted Answer

To decrease pressure for filling blood

Question 14

Which of the following statements about the T wave on an ECG is correct?

Accepted Answer

It represents ventricular repolarization

Question 15

A patient has an end-diastolic volume (EDV) of $120\ mL$ and an end-systolic volume (ESV) of $50\ mL$. What is the stroke volume (SV)? Use the formula $SV = EDV - ESV$.

Accepted Answer

$SV = 120\ mL - 50\ mL = 70\ mL$

Question 16

Which of the following best describes the function of Purkinje fibers in the heart?

Accepted Answer

Transmit electrical signals down the atrioventricular bundle to the ventricles

Question 17

Which of the following is true regarding the interpretation of an ECG?

Accepted Answer

A normal ECG should have one QRS complex for each P wave

Question 18

Which of the following would most likely result in bradycardia as seen on an ECG?

Accepted Answer

A heart rate of 55 bpm

Question 19

Which of the following best explains why the AV node delays the conduction of the action potential?

Accepted Answer

To allow the atria to finish contracting and complete ventricular filling

Question 20

Which of the following is the correct definition of end-systolic volume (ESV)?

Accepted Answer

The volume of blood in the ventricle at the end of ventricular contraction

Cardiovascular Physiology: The Heart as a Pump and the Cardiac Cycle

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