Question 1

Which structure is primarily responsible for the rapid electrical communication between adjacent cardiomyocytes in the heart?

Accepted Answer

Gap junctions

Question 2

During the cardiac cycle, which event directly causes the first heart sound (S1)?

Accepted Answer

Closure of the atrioventricular (AV) valves

Question 3

A patient has a mutation that impairs the function of desmosomes in their cardiac muscle. Which of the following is the most likely consequence?

Accepted Answer

Reduced mechanical strength and increased risk of cell separation during contraction

Question 4

Which of the following best describes the role of the sinoatrial (SA) node in cardiac physiology?

Accepted Answer

It acts as the primary pacemaker, initiating the heartbeat

Question 5

Which phase of the cardiac action potential in contractile cardiomyocytes is primarily responsible for the absolute refractory period?

Accepted Answer

Phase 2 (plateau phase)

Question 6

If the left ventricle fails to pump effectively, which of the following is a likely clinical consequence?

Accepted Answer

Pulmonary edema

Question 7

Which of the following equations correctly represents cardiac output ($$CO$$)?

Accepted Answer

$$CO = HR 	imes SV$$

Question 8

A drug that increases the permeability of pacemaker cells to sodium ($$Na^+) $$would most likely have which effect on heart rate?

Accepted Answer

Increase heart rate by accelerating depolarization

Question 9

Which of the following best explains why the heart cannot undergo tetanus (sustained contraction) like skeletal muscle?

Accepted Answer

The absolute refractory period in cardiac muscle is nearly as long as the contraction itself

Question 10

A patient experiences a sudden drop in blood pressure. Which of the following is the correct sequence of the baroreceptor reflex response?

Accepted Answer

Decreased baroreceptor firing → increased sympathetic output → increased heart rate

Question 11

Which of the following changes would most likely increase stroke volume ($$SV$$)?

Accepted Answer

Increased preload

Question 12

During which phase of the cardiac cycle are all four heart valves closed and the ventricles are relaxing?

Accepted Answer

Isovolumetric relaxation

Question 13

Which neurotransmitter is released by sympathetic postganglionic fibers to increase heart rate?

Accepted Answer

Norepinephrine

Question 14

A patient has a heart rate of 80 beats per minute and a stroke volume of 70 mL. What is their cardiac output ($$CO$$)?

Accepted Answer

$$CO = 5600\ \mathrm{mL/min}$$

Question 15

Which of the following best describes the effect of increased vagal (parasympathetic) tone on the heart?

Accepted Answer

Decreases heart rate

Question 16

Which of the following is a direct effect of sympathetic stimulation on the heart?

Accepted Answer

Increased force of ventricular contraction

Question 17

Which of the following best explains why venous return increases during exercise?

Accepted Answer

Increased skeletal muscle contractions compress veins and push blood toward the heart

Question 18

Which of the following would most likely result from a loss of function in the gap junctions of cardiac muscle?

Accepted Answer

Disrupted electrical conduction and possible arrhythmias

Question 19

Which of the following best describes the Frank-Starling law of the heart?

Accepted Answer

The greater the stretch of ventricular muscle fibers at end-diastole, the greater the force of contraction

Question 20

A patient is given a drug that blocks muscarinic acetylcholine receptors in the heart. What is the most likely effect?

Accepted Answer

Increased heart rate due to inhibition of parasympathetic effects

Cardiovascular System: Heart Physiology (Chapter 17) – Study Notes

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