Question 1

Which of the following best explains why the heart requires two separate pumps (right and left sides) rather than a single pump?

Accepted Answer

To ensure that oxygenated and deoxygenated blood do not mix, allowing for efficient gas exchange in the lungs and delivery to systemic tissues.

Question 2

During which phase of the cardiac cycle are both the atrioventricular (AV) valves and semilunar valves closed, and what is the significance of this phase?

Accepted Answer

Isovolumic ventricular contraction; this phase allows ventricular pressure to rise rapidly without a change in volume, preparing for ejection.

Question 3

A patient has an end-diastolic volume (EDV) of 140 mL and an end-systolic volume (ESV) of 60 mL. What is their stroke volume (SV)?

Accepted Answer

$$SV = EDV - ESV = 140\ \mathrm{mL} - 60\ \mathrm{mL} = 80\ \mathrm{mL}$$

Question 4

Which of the following best describes the role of gap junctions in cardiac contractile cells?

Accepted Answer

They allow direct electrical communication between adjacent cells, enabling coordinated contraction.

Question 5

Why is tetanus (sustained contraction) prevented in ventricular muscle, and what is the physiological significance?

Accepted Answer

The prolonged cardiac action potential creates a refractory period that overlaps with contraction, preventing summation and allowing the heart to relax and refill.

Question 6

If the function of the Na⁺/K⁺-ATPase in cardiac myocytes is inhibited, what is the most likely immediate effect on cardiac excitation–contraction coupling?

Accepted Answer

The Na⁺ gradient would decrease, impairing the Na⁺/Ca²⁺ exchanger (NCX) and reducing Ca²⁺ removal from the cytosol, leading to prolonged contraction.

Question 7

Which sequence correctly traces the conduction pathway of electrical impulses through the heart?

Accepted Answer

SA node → atrial pathways → AV node → AV bundle (bundle of His) → bundle branches → Purkinje fibers → ventricular myocardium

Question 8

A patient’s ECG shows an absence of P waves and an irregularly irregular rhythm. Which condition is most consistent with these findings?

Accepted Answer

Atrial fibrillation

Question 9

Which of the following changes would most likely occur if the L-type Ca²⁺ channels in ventricular myocytes were blocked?

Accepted Answer

Reduced Ca²⁺ influx would decrease the trigger for SR Ca²⁺ release, leading to weaker contractions.

Question 10

Which of the following best explains the Frank–Starling mechanism in the heart?

Accepted Answer

Increased ventricular filling stretches cardiac muscle fibers, resulting in greater force of contraction and increased stroke volume.

Question 11

If a patient’s end-diastolic volume (EDV) increases while their end-systolic volume (ESV) remains constant, what happens to their stroke volume (SV)?

Accepted Answer

Stroke volume increases because $$SV = EDV - ESV.$$

Question 12

Which of the following best describes the effect of sympathetic stimulation on the SA node?

Accepted Answer

It increases the slope of the pacemaker potential, causing more frequent threshold crossings and a higher heart rate.

Question 13

A patient has a heart rate (HR) of 75 beats per minute and a stroke volume (SV) of 70 mL per beat. What is their cardiac output (CO)?

Accepted Answer

$$CO = HR 	imes SV = 75\ \mathrm{beats/min} 	imes 70\ \mathrm{mL/beat} = 5250\ \mathrm{mL/min}$$

Question 14

Which of the following is true regarding the relationship between the left ventricular and aortic pressures during ventricular ejection?

Accepted Answer

They track closely because the open aortic valve allows flow with only a small pressure gradient.

Question 15

Which of the following would most likely occur if Ca²⁺ reuptake into the sarcoplasmic reticulum (SR) is slowed in cardiac myocytes?

Accepted Answer

Relaxation would be delayed, leading to prolonged contraction and possible diastolic dysfunction.

Question 16

Which of the following best distinguishes the action potential of a cardiac contractile cell from that of a skeletal muscle cell?

Accepted Answer

Cardiac contractile cells have a prolonged plateau phase due to Ca²⁺ influx, resulting in a longer refractory period.

Question 17

If the SA node fails but the AV node remains functional, what is the expected effect on heart rate and ECG?

Accepted Answer

Heart rate decreases to about 50 bpm, and the ECG shows absent or abnormal P waves with preserved QRS complexes.

Question 18

Which of the following best explains why there is no change in ventricular volume during the isovolumic phases of the cardiac cycle?

Accepted Answer

Both the AV and semilunar valves are closed, preventing blood from entering or leaving the ventricle.

Question 19

Which of the following changes would most likely increase cardiac output (CO), assuming all other variables remain constant?

Accepted Answer

An increase in both heart rate (HR) and stroke volume (SV), since $$CO = HR 	imes SV.$$

Question 20

Which of the following best describes the effect of parasympathetic stimulation on the pacemaker cells of the heart?

Accepted Answer

It increases K⁺ permeability and decreases Ca²⁺ permeability, hyperpolarizing the cell and slowing the heart rate.

Cardiovascular Physiology: Heart Function, Cardiac Cycle, and Control Mechanisms

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