Q: A person at rest has an end-diastolic volume ($$EDV) of 135 mL $$and an end-systolic volume ($$ESV) of 65 mL. $$What is their stroke volume ($$SV$$)?

$$SV = 135 \text{ mL} - 65 \text{ mL} = 70 \text{ mL}$$

Question 1

Which of the following best explains why the left ventricle of the heart has a thicker wall than the right ventricle?

Accepted Answer

Because it pumps blood to the entire systemic circuit, requiring greater force to overcome higher resistance.

Question 2

During which phase of the cardiac cycle are the atrioventricular (AV) valves open and the semilunar valves closed?

Accepted Answer

Late diastole

Question 3

Which of the following statements about veins is correct?

Accepted Answer

Veins carry blood toward the heart, regardless of oxygenation status.

Question 4

A patient has a mutation that prevents the inactivation of voltage-gated sodium channels in cardiac myocytes. Which of the following would most likely be affected?

Accepted Answer

The absolute refractory period would be shortened, increasing the risk of tetanus in the heart.

Question 5

Which of the following best describes the function of the plateau phase in the cardiac action potential?

Accepted Answer

It prevents summation and tetanus by extending the refractory period to match the duration of contraction.

Question 6

If the semilunar valves failed to close properly, which of the following would most likely occur?

Accepted Answer

Blood would flow backward from the arteries into the ventricles during ventricular relaxation.

Question 7

Which of the following equations correctly calculates stroke volume ($$SV) $$based on end-diastolic volume ($$EDV) $$and end-systolic volume ($$ESV$$)?

Accepted Answer

$$SV = EDV - ESV$$

Question 8

A person at rest has an end-diastolic volume ($$EDV) of 135 mL $$and an end-systolic volume ($$ESV) of 65 mL. $$What is their stroke volume ($$SV$$)?

Accepted Answer

$$SV = 135 	ext{ mL} - 65 	ext{ mL} = 70 	ext{ mL}$$

Question 9

Which of the following is a direct result of the closing of the atrioventricular (AV) valves?

Accepted Answer

The first heart sound ("lub") is produced.

Question 10

Which of the following best explains why the heart requires its own coronary circulation?

Accepted Answer

The cardiac muscle cells are too far from the blood in the chambers for effective diffusion of oxygen and nutrients.

Question 11

Which of the following events occurs immediately after ventricular pressure exceeds aortic pressure during the cardiac cycle?

Accepted Answer

The semilunar valves open, allowing blood to be ejected into the aorta.

Question 12

Which of the following is NOT a primary function of the circulatory system?

Accepted Answer

Synthesis of hormones.

Question 13

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

Accepted Answer

They allow for mechanical and electrical coupling between cardiac myocytes, enabling coordinated contraction.

Question 14

Which of the following statements about the pulmonary and systemic circuits is correct?

Accepted Answer

The pulmonary circuit carries deoxygenated blood from the right ventricle to the lungs and returns oxygenated blood to the left atrium.

Question 15

Which of the following best explains why blood flows from the atria to the ventricles during late diastole?

Accepted Answer

Atrial pressure is higher than ventricular pressure, and the AV valves are open.

Question 16

Which of the following ions is primarily responsible for the plateau phase of the cardiac action potential?

Accepted Answer

Calcium ($$Ca^{2+})$$

Question 17

A patient is found to have a blockage in the pulmonary artery. Which of the following would most likely be a direct consequence?

Accepted Answer

Decreased blood flow to the lungs, resulting in reduced oxygenation of blood.

Question 18

Which of the following best describes the relationship between pressure and volume in the heart during ventricular contraction?

Accepted Answer

As ventricular volume decreases, pressure increases.

Question 19

Which of the following is the correct sequence of events during the cardiac cycle?

Accepted Answer

Atrial systole → Isovolumic ventricular contraction → Ventricular systole → Isovolumic ventricular relaxation → Late diastole

Question 20

Which of the following is true regarding the color of human blood?

Accepted Answer

Blood is always red due to the presence of hemoglobin, regardless of oxygenation.

The Cardiovascular System: Structure, Function, and Cardiac Muscle Physiology

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