Q: A patient has a heart rate of $$75$$ bpm and a stroke volume of $$80 mL/$$beat. What is their cardiac output ($$CO$$)? Use the formula $$CO = HR \times SV.$$

$$CO = 75 \times 80 = 6,000 mL/$$min ($$6.0 L/$$min)

Question 1

Which event on the ECG corresponds to the closure of the atrioventricular (AV) valves and the beginning of ventricular systole?

Accepted Answer

QRS complex

Question 2

During which phase of the cardiac cycle are the semilunar valves open and blood is ejected from the ventricles?

Accepted Answer

Ventricular systole (second phase)

Question 3

What mechanical event in the heart immediately follows the T wave on the ECG?

Accepted Answer

Ventricular relaxation (diastole)

Question 4

If a patient’s ECG shows a prolonged QRS complex (greater than $$0.12$$ seconds), what is the most likely physiological explanation?

Accepted Answer

Delayed ventricular depolarization

Question 5

Which of the following best describes the relationship between the P wave and atrial systole?

Accepted Answer

The P wave represents atrial depolarization, which triggers atrial systole.

Question 6

During which phase are all heart valves closed, and what is the significance of this phase?

Accepted Answer

Isovolumetric contraction; allows pressure to build in the ventricles before ejection

Question 7

Which of the following correctly matches the ECG event with the corresponding mechanical event in the heart?

Accepted Answer

T wave – ventricular repolarization

Question 8

A patient has a heart rate of $$75$$ bpm and a stroke volume of $$80 mL/$$beat. What is their cardiac output ($$CO$$)? Use the formula $$CO = HR 	imes SV.$$

Accepted Answer

$$CO = 75 	imes 80 = 6,000 mL/$$min ($$6.0 L/$$min)

Question 9

Which phase of the cardiac cycle is most associated with the S2 heart sound?

Accepted Answer

Ventricular diastole (early)

Question 10

If the PR interval on an ECG is longer than $$0.20$$ seconds, what does this indicate?

Accepted Answer

Delayed conduction through the AV node

Question 11

During which phase of the cardiac cycle does ventricular filling occur most rapidly?

Accepted Answer

Ventricular diastole (early)

Question 12

Which of the following best explains why the QRS complex is larger than the P wave on an ECG?

Accepted Answer

Ventricular muscle mass is greater than atrial muscle mass

Question 13

A patient’s ECG shows a regular rhythm with a heart rate of $$55$$ bpm, one P wave before every QRS, and a PR interval of $$0.16$$ seconds. What is the most likely diagnosis?

Accepted Answer

Sinus bradycardia

Question 14

Which of the following best describes the function of the AV node during the cardiac cycle?

Accepted Answer

It delays the electrical impulse to allow ventricular filling

Question 15

If a patient has a ventricular septal defect (VSD), which of the following changes is most likely to be observed?

Accepted Answer

Decreased effective systemic stroke volume

Cardiovascular System: Heart Anatomy, Physiology, and Blood Vessels

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