$$CO = 80 \times 70 = 5600\ mL/min$$

Question 1

Which of the following best describes the role of intercalated discs in cardiac muscle tissue?

Accepted Answer

They provide electrical and mechanical connections between cardiomyocytes.

Question 2

During which phase of the cardiac cycle does the QRS complex appear on an ECG, and what does it represent?

Accepted Answer

Phase 3; ventricular depolarization

Question 3

A patient’s ECG shows an abnormally long flatline after the P wave. Which part of the cardiac conduction system is most likely malfunctioning?

Accepted Answer

Atrioventricular (AV) node

Question 4

Which of the following is a key difference between contractile cardiac muscle cells and skeletal muscle cells?

Accepted Answer

Cardiac muscle cells are striated, short, and branched with one or two nuclei.

Question 5

Which equation correctly represents cardiac output?

Accepted Answer

$$CO = SV 	imes HR$$

Question 6

If a person’s heart rate is 80 beats per minute and their stroke volume is 70 mL/beat, what is their cardiac output?

Accepted Answer

$$CO = 80 	imes 70 = 5600\ mL/min$$

Question 7

Which of the following best explains why tetanus (sustained contraction) is not possible in cardiac muscle?

Accepted Answer

The refractory period in cardiac muscle is long, preventing summation of contractions.

Question 8

Which event is represented by the T wave on an ECG?

Accepted Answer

Ventricular repolarization

Question 9

Which of the following statements about the SA node is correct?

Accepted Answer

It is the pacemaker of the heart and initiates all heartbeats.

Question 10

A patient has a heart rate of 60 beats per minute and a cardiac output of 4800 mL/min. What is their stroke volume?

Accepted Answer

$$SV = 4800 / 60 = 80\ mL/beat$$

Question 11

Which of the following best describes the effect of sympathetic nerve fibers on the heart?

Accepted Answer

They increase heart rate and force of contraction.

Question 12

Which of the following is true regarding the source of calcium ions for contraction in cardiac muscle cells?

Accepted Answer

Calcium comes from both the sarcoplasmic reticulum and extracellular fluid.

Question 13

Which phase of the cardiac cycle is associated with the closure of the AV valves and the production of the 'lub' heart sound?

Accepted Answer

Phase 3

Question 14

Which of the following best explains why the heart requires a rich supply of oxygen?

Accepted Answer

Cardiac muscle cells rely almost exclusively on aerobic respiration for ATP production.

Question 15

Which of the following is a function of gap junctions in cardiac muscle?

Accepted Answer

They electrically connect myocytes, allowing coordinated contraction.

Question 16

Which of the following best describes the sequence of electrical conduction in the heart?

Accepted Answer

SA node → AV node → AV bundle → Purkinje fibers

Question 17

Which of the following is true about the cardiac cycle during exercise compared to rest?

Accepted Answer

As much as 90% of the blood in the ventricles is expelled during exercise.

Question 18

Which of the following is a correct statement about the ECG?

Accepted Answer

The P wave reflects depolarization of the atria.

Question 19

A patient’s ECG shows no P wave but a normal QRS complex and T wave. Which part of the conduction system is most likely not functioning?

Accepted Answer

SA node

Question 20

Which of the following best explains why the AV node slows down the electrical signal?

Accepted Answer

To allow the atria to fully contract and the ventricles to fill with blood before ventricular contraction.

PART 2: The Cardiovascular System – Cardiac Muscle, Conduction, and Cardiac Cycle

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