Q: A patient has a heart rate of 80 beats per minute and a stroke volume of 65 mL/beat. What is their cardiac output ($$CO$$)?

$$CO = 80 \times 65 = 5200\ \text{mL/min}$$

Question 1

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

Accepted Answer

It pumps blood to the entire body through the systemic circuit, which has higher resistance.

Question 2

A patient is diagnosed with a blockage in the pulmonary trunk. Which chamber of the heart will be directly affected first?

Accepted Answer

Right ventricle

Question 3

Which of the following statements about cardiac muscle is correct?

Accepted Answer

Cardiac muscle cells are connected by intercalated discs containing desmosomes and gap junctions.

Question 4

During the cardiac cycle, which event occurs immediately after the QRS complex on an ECG?

Accepted Answer

Ventricular depolarization

Question 5

A patient has a heart rate of 80 beats per minute and a stroke volume of 65 mL/beat. What is their cardiac output ($$CO$$)?

Accepted Answer

$$CO = 80 	imes 65 = 5200\ 	ext{mL/min}$$

Question 6

Which of the following best describes the function of the chordae tendineae?

Accepted Answer

They anchor the atrioventricular valves to the papillary muscles, preventing valve prolapse.

Question 7

If the sinoatrial (SA) node becomes nonfunctional, which of the following is most likely to occur?

Accepted Answer

The atrioventricular (AV) node will take over as pacemaker, resulting in a slower heart rate.

Question 8

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

Accepted Answer

Increased heart rate and increased contractility

Question 9

A patient with hypertension (high blood pressure) is likely to experience which of the following changes in stroke volume ($$SV$$), assuming all other factors remain constant?

Accepted Answer

$$SV$$ decreases due to increased afterload.

Question 10

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

Accepted Answer

Cardiac muscle has a long absolute refractory period, preventing summation of contractions.

Question 11

Which of the following is the correct sequence of structures that a cardiac action potential travels through during normal conduction?

Accepted Answer

SA node → AV node → AV bundle (bundle of His) → bundle branches → Purkinje fibers

Question 12

A patient’s ECG shows an absence of P waves and a heart rate of 45 beats per minute. Which condition is most likely present?

Accepted Answer

Junctional rhythm with AV node pacing the heart

Question 13

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

Accepted Answer

The greater the stretch of cardiac muscle cells (preload), the greater the force of contraction.

Question 14

Which of the following would most likely increase end diastolic volume ($$EDV) in $$the left ventricle?

Accepted Answer

Increased venous return due to exercise

Question 15

Which of the following is true regarding the energy requirements of cardiac muscle?

Accepted Answer

Cardiac muscle relies almost exclusively on aerobic respiration for ATP production.

Question 16

A patient is experiencing rapid, irregular contractions of the ventricles, resulting in ineffective pumping of blood. Which condition does this describe?

Accepted Answer

Ventricular fibrillation

Question 17

Which of the following best describes the function of gap junctions in cardiac muscle?

Accepted Answer

They allow ions to pass between cells, enabling the heart to act as a functional syncytium.

Question 18

If a patient’s end diastolic volume ($$EDV) is 120 mL $$and their end systolic volume ($$ESV) is 50 mL$$, what is their stroke volume ($$SV$$)?

Accepted Answer

$$SV = 120 - 50 = 70\ 	ext{mL}$$

Question 19

Which of the following would most likely cause a decrease in heart rate?

Accepted Answer

Increased parasympathetic (vagal) stimulation

Question 20

A patient is given a calcium channel blocker. What effect would this have on the heart?

Accepted Answer

It would decrease contractility by reducing calcium influx.

Chapter 18: The Heart – Anatomy, Physiology, and Circulation

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