Q: Calculate the cardiac output (CO) for a patient with a heart rate (HR) of 90 beats/min and a stroke volume (SV) of 60 mL/beat. Use the formula $$CO = HR \times SV.$$

$$CO = 90 \times 60 = 5400 mL/$$min

Question 1

Which of the following best explains why the heart can continue to beat even if all nervous connections to the brain are severed?

Accepted Answer

The heart contains autorhythmic cells that generate their own action potentials.

Question 2

A patient presents with a prolonged Q-T interval on their ECG. Which of the following is the most likely consequence if this abnormality is not addressed?

Accepted Answer

Increased risk of ventricular arrhythmias

Question 3

During the cardiac cycle, which event is directly responsible for the first heart sound ("lub")?

Accepted Answer

Closing of the atrioventricular (AV) valves at the beginning of ventricular systole

Question 4

Which of the following best describes the sequence of excitation in the intrinsic conduction system of the heart?

Accepted Answer

Sinoatrial node → Atrioventricular node → Atrioventricular bundle → Bundle branches → Purkinje fibers

Question 5

A patient is found to have an incompetent mitral valve. Which of the following heart sounds or findings would most likely be present during auscultation?

Accepted Answer

A swishing sound due to blood regurgitating from ventricle to atrium

Question 6

Which ion movement is primarily responsible for the plateau phase of the contractile cardiac muscle cell action potential?

Accepted Answer

Influx of Ca$$^{2+}$$ through slow channels

Question 7

Calculate the cardiac output (CO) for a patient with a heart rate (HR) of 90 beats/min and a stroke volume (SV) of 60 mL/beat. Use the formula $$CO = HR 	imes SV.$$

Accepted Answer

$$CO = 90 	imes 60 = 5400 mL/$$min

Question 8

A patient has a heart block due to a defective AV node. Which of the following is the most likely effect on the heart's rhythm?

Accepted Answer

Ventricles beat at their own intrinsic rate, which is too slow to maintain adequate circulation.

Question 9

Which of the following changes would most likely be seen on an ECG if a patient has hyperkalemia (elevated K$$^{+}$$ levels)?

Accepted Answer

Abnormal T wave due to repolarization issues

Question 10

Which of the following best describes the effect of sympathetic nervous system activation on the heart?

Accepted Answer

Increases heart rate and contractility via norepinephrine binding to $$\$$beta_1$$-adrenergic receptors

Question 11

A 25-year-old athlete has a resting cardiac output (CO) of 5.5 L/min and a maximal CO of 33 L/min during intense exercise. What is this athlete's cardiac reserve?

Accepted Answer

$$33 - 5.5 = 27.5 L/$$min

Question 12

Which phase of the cardiac cycle is characterized by all heart valves being closed and no change in ventricular volume, despite ongoing contraction?

Accepted Answer

Isovolumetric contraction

Question 13

A patient experiences a premature contraction (extrasystole) after consuming excessive caffeine. Which of the following best explains the sensation of a 'thud' felt during the next heartbeat?

Accepted Answer

The heart has more time to fill, resulting in a larger volume of blood being ejected on the next beat.

Question 14

Which of the following would most likely result from a stenotic aortic valve?

Accepted Answer

A high-pitched or clicking sound as blood is forced through a narrow opening

Question 15

Which of the following best describes the role of the AV bundle (bundle of His) in the heart's conduction system?

Accepted Answer

It is the only electrical connection between the atria and ventricles.

Question 16

Which of the following is true regarding the P wave on an ECG?

Accepted Answer

It represents depolarization of the SA node and atria.

Question 17

A patient with a defective SA node develops an ectopic focus in the AV node. What is the expected heart rate (junctional rhythm) in this scenario?

Accepted Answer

40-60 beats per minute

Question 18

Which of the following best explains why the Purkinje fibers are more elaborate on the left side of the heart?

Accepted Answer

The left ventricle has a thicker wall and requires more extensive conduction for coordinated contraction.

Question 19

Which of the following would most likely occur if the S-T segment on an ECG is elevated or depressed?

Accepted Answer

Cardiac ischemia

Chapter 17: The Cardiovascular System – The Heart (Mini-Textbook Study Notes)

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