Q: A patient has a heart rate of 80 beats per minute and a stroke volume of 75 mL. What is their cardiac output?

$CO = HR \times SV = 80 \times 75 = 6000\ \text{mL/min}$

Question 1

Which of the following best describes the function of the pericardial fluid?

Accepted Answer

It lubricates the serous layers and reduces friction between the heart and pericardium.

Question 2

A patient is diagnosed with cardiac tamponade after a chest injury. Which of the following best explains the physiological consequence of this condition?

Accepted Answer

The movement of the heart is restricted due to excess fluid in the pericardial cavity.

Question 3

Which structure electrically insulates the atria from the ventricles and stabilizes the positions of the heart valves?

Accepted Answer

Cardiac skeleton

Question 4

During ventricular systole, which valves are open and which are closed?

Accepted Answer

Atrioventricular valves are closed; semilunar valves are open.

Question 5

A myocardial infarction (MI) is most commonly caused by which of the following events?

Accepted Answer

A thrombus formation at an atherosclerotic plaque in a coronary artery

Question 6

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

Accepted Answer

It generates 4–6 times more pressure to pump blood through the systemic circuit.

Question 7

Which of the following is the correct sequence of impulse conduction through the heart?

Accepted Answer

SA node → AV node → AV bundle → Bundle branches → Purkinje fibers

Question 8

Which of the following best describes the Frank–Starling principle?

Accepted Answer

As the end-diastolic volume (EDV) increases, the stroke volume also increases.

Question 9

A patient has a heart rate of 80 beats per minute and a stroke volume of 75 mL. What is their cardiac output?

Accepted Answer

$CO = HR 	imes SV = 80 	imes 75 = 6000\ 	ext{mL/min}$

Question 10

Which of the following would most likely increase the afterload on the left ventricle?

Accepted Answer

Peripheral vasoconstriction

Question 11

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

Accepted Answer

Increased heart rate and contractility

Question 12

Which of the following best describes the role of calcium ions in cardiac muscle contraction?

Accepted Answer

Extracellular calcium ions enter during the plateau phase and trigger additional calcium release from the sarcoplasmic reticulum.

Question 13

A patient’s ECG shows a prolonged P–R interval. What does this most likely indicate?

Accepted Answer

Damage to the AV node or conducting pathways

Question 14

Which of the following is a feature unique to cardiac muscle cells compared to skeletal muscle cells?

Accepted Answer

Presence of intercalated discs for electrical and mechanical connection

Question 15

Which of the following best explains why the heart cannot undergo tetanus?

Accepted Answer

The long refractory period in cardiac muscle prevents summation and tetanus.

Question 16

Which of the following is the correct formula for ejection fraction (EF)?

Accepted Answer

$EF = \frac{SV}{EDV} 	imes 100$

Question 17

Which of the following is a risk factor for both coronary artery disease (CAD) and myocardial infarction (MI)?

Accepted Answer

High cholesterol and LDLs

Question 18

Which of the following best describes the Bainbridge reflex?

Accepted Answer

A reflex that increases heart rate in response to increased venous return (atrial stretch)

Question 19

Which of the following drugs would most likely be used to reduce the risk of clot formation in a patient with CAD?

Accepted Answer

Aspirin

Question 20

A patient has an end-diastolic volume (EDV) of 120 mL and an end-systolic volume (ESV) of 50 mL. What is their stroke volume (SV)?

Accepted Answer

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

Chapter 20: The Heart – Anatomy, Physiology, and Regulation

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