Question 1

Which type of cardiac myocyte is responsible for initiating the depolarization of the entire heart without requiring nervous system stimulation?

Accepted Answer

Pacemaker cells

Question 2

What is the primary benefit of the longer absolute refractory period in cardiac muscle fibers compared to skeletal muscle fibers?

Accepted Answer

It prevents tetanic contractions, ensuring efficient ejection of blood

Question 3

Which structure in the intrinsic cardiac conduction system delays the electrical impulse to allow the atria to contract before the ventricles?

Accepted Answer

Atrioventricular (AV) node

Question 4

A patient presents with a heart rate of 45 beats per minute. Which part of the conduction system is most likely acting as the pacemaker?

Accepted Answer

Atrioventricular (AV) node

Question 5

Which of the following best explains why tetanic contractions cannot occur in cardiac muscle?

Accepted Answer

Cardiac muscle fibers have a longer absolute refractory period

Question 6

During which phase of the cardiac cycle does ventricular contraction occur, and what is this phase called?

Accepted Answer

Systole; contraction

Question 7

If the sinoatrial (SA) node fails to function, what is the most likely consequence for heart rate?

Accepted Answer

Heart rate will decrease and be set by the AV node

Question 8

Which of the following is a direct result of the longer action potential duration in cardiac muscle compared to skeletal muscle?

Accepted Answer

Sustained contraction for efficient blood ejection

Question 9

Which component of the cardiac conduction system directly depolarizes the contractile cells of both ventricles?

Accepted Answer

Subendocardial conducting network (Purkinje fibers)

Question 10

A patient’s ECG shows a prolonged PR interval greater than 0.2 seconds. What is the most likely diagnosis?

Accepted Answer

First degree heart block

Question 11

Which formula correctly calculates cardiac output ($CO$) in terms of stroke volume ($SV$) and heart rate ($HR$)?

Accepted Answer

$CO = SV 	imes HR$

Question 12

Given an end diastolic volume ($EDV$) of 120 ml and an end systolic volume ($ESV$) of 50 ml, what is the stroke volume ($SV$)?

Accepted Answer

$SV = EDV - ESV = 70$ ml

Question 13

Which of the following is NOT a function of pacemaker cells in the heart?

Accepted Answer

Require nervous system stimulation to function

Question 14

Which event in the cardiac cycle immediately follows the QRS complex on an ECG?

Accepted Answer

Ventricular contraction (systole)

Question 15

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

Accepted Answer

It connects the atria to the ventricles, allowing impulse conduction

Question 16

Which of the following would most likely result if the absolute refractory period in cardiac muscle were shortened to resemble that of skeletal muscle?

Accepted Answer

Tetanic contractions and impaired heart function

Question 17

Which of the following statements about contractile cells in the heart is correct?

Accepted Answer

They are responsible for the contraction of the myocardium

Question 18

Which phase of the cardiac action potential is responsible for the long refractory period in cardiac muscle?

Accepted Answer

Plateau phase

Question 19

A patient is found to have a heart rate of 30 beats per minute. Which part of the conduction system is most likely acting as the pacemaker?

Accepted Answer

Ventricular cells

Question 20

Which of the following is a key difference between the action potential of cardiac muscle and skeletal muscle?

Accepted Answer

Cardiac muscle action potential includes a plateau phase, prolonging contraction

Cardiovascular System: Cardiac Muscle, Conduction, and Electrical Activity

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