Cardiac Dysrhythmias Study Guide Part One
Cardiac Dysrhythmias: Electrical Conduction System
Multiple Choice Test
1. What is the primary pacemaker of the heart?
a) Atrioventricular (AV) node
b) Sinoatrial (SA) node
c) Bundle of His
d) Purkinje fibers
Answer: b) Sinoatrial (SA) node
Explanation: The SA node is the primary pacemaker of the heart, initiating
the heartbeat.
2. What is the normal rate of automaticity for the SA node?
a) 40 – 60 bpm
b) 20 – 40 bpm
c) 60 – 100 bpm
d) 100 – 120 bpm
Answer: c) 60 – 100 bpm
Explanation: The SA node typically fires at a rate of 60 to 100 beats per
minute.
3. Where is the SA node located?
a) Right atrium
b) Left ventricle
c) Right ventricle
d) Left atrium
Answer: a) Right atrium
Explanation: The SA node is situated in the right atrium of the heart.
4. Which node is considered the secondary pacemaker of the heart?
a) Sinoatrial (SA) node
b) Atrioventricular (AV) node
c) Bundle of His
d) Purkinje fibers
Answer: b) Atrioventricular (AV) node
Explanation: The AV node acts as the secondary pacemaker when the SA
node fails.
5. What is the normal rate of automaticity for the Atrioventricular
(AV) node?
a) 60 – 100 bpm
b) 40 – 60 bpm
c) 20 – 40 bpm
d) 100 – 120 bpm
Answer: b) 40 – 60 bpm
Explanation: The AV node fires at a rate of 40 to 60 beats per minute.
6. What happens if both the SA and AV nodes fail to generate an
impulse?
,a) The atria stop contracting
b) The Bundle of His takes over
c) The Purkinje fibers take over as pacemaker
d) The heart ceases to function
Answer: c) The Purkinje fibers take over as pacemaker
Explanation: If both the SA and AV nodes fail, the Purkinje fibers act as a
last resort pacemaker with a rate of 20–40 bpm.
7. Which of the following has the fastest rate of automaticity?
a) SA node
b) AV node
c) Bundle of His
d) Purkinje fibers
Answer: a) SA node
Explanation: The SA node has the fastest intrinsic rate of automaticity,
between 60-100 bpm.
8. Which part of the heart's electrical conduction system has the
slowest intrinsic firing rate?
a) SA node
b) AV node
c) Purkinje fibers
d) Bundle of His
Answer: c) Purkinje fibers
Explanation: The Purkinje fibers fire at a rate of 20–40 bpm, the slowest in
the conduction system.
9. Which of the following describes the location and function of the
Bundle of His?
a) Located in the right atrium; primary pacemaker
b) Located between the atria and ventricles; conducts impulses to the
ventricles
c) Located in the ventricles; initiates contraction of the ventricles
d) Located in the left atrium; slows down the heart rate
Answer: b) Located between the atria and ventricles; conducts
impulses to the ventricles
Explanation: The Bundle of His transmits electrical impulses from the AV
node to the ventricles.
10. What role do the Purkinje fibers play in the heart's conduction
system?
a) They slow down the heart rate.
b) They initiate electrical impulses in the SA node.
c) They conduct electrical impulses to the ventricular myocardium, causing
contraction.
d) They generate electrical impulses that override the SA node.
Answer: c) They conduct electrical impulses to the ventricular
myocardium, causing contraction
Explanation: Purkinje fibers ensure that the ventricles contract in
coordination to pump blood effectively.
,11. Which part of the heart is most responsible for the delay in
electrical conduction, allowing the ventricles time to fill with blood?
a) SA node
b) AV node
c) Bundle of His
d) Purkinje fibers
Answer: b) AV node
Explanation: The AV node slows down the electrical impulse to allow the
ventricles time to fill before contraction.
12. What term is used to describe the heart's ability to generate its
own electrical impulses without external stimuli?
a) Contractility
b) Conductivity
c) Automaticity
d) Excitability
Answer: c) Automaticity
Explanation: Automaticity is the heart's ability to generate its own electrical
impulses.
13. What is the electrical charge inside the heart cells during the
resting phase?
a) Positive
b) Neutral
c) Negative
d) Alternating
Answer: c) Negative
Explanation: During the resting phase, the inside of heart cells is negatively
charged compared to the outside.
14. Which phase of the cardiac cycle involves the depolarization of
the ventricles, leading to their contraction?
a) Diastole
b) Repolarization
c) Systole
d) Resting potential
Answer: c) Systole
Explanation: Systole is when the ventricles depolarize and contract to pump
blood.
15. What is the refractory period in cardiac cells?
a) A period of fast depolarization
b) A period when cells are unable to respond to a new stimulus
c) The time when cells generate an action potential
d) The moment when cells fully repolarize
Answer: b) A period when cells are unable to respond to a new
stimulus
Explanation: The refractory period is the phase during which cardiac cells
cannot be excited by another impulse.
16. What happens during repolarization of the cardiac cells?
, a) Cells return to a resting state
b) Cells are unable to contract
c) Cells become depolarized again
d) Cells generate an action potential
Answer: a) Cells return to a resting state
Explanation: Repolarization restores the negative charge inside the cell,
allowing it to return to its resting state.
17. Which electrolyte is primarily responsible for the depolarization
of cardiac cells?
a) Sodium (Na⁺)
b) Potassium (K⁺)
c) Calcium (Ca²⁺)
d) Chloride (Cl⁻)
Answer: a) Sodium (Na⁺)
Explanation: Sodium ions enter the cell during depolarization, causing the
interior of the cell to become more positive.
18. What is the role of calcium (Ca²⁺) in the cardiac action potential?
a) Causes depolarization of the SA node
b) Stabilizes the cell membrane
c) Aids in repolarization
d) Initiates myocardial contraction
Answer: d) Initiates myocardial contraction
Explanation: Calcium ions are responsible for the contraction of myocardial
cells after depolarization.
19. Which dysrhythmia is most likely to occur when the electrical
conduction is initiated from the AV node instead of the SA node?
a) Sinus tachycardia
b) Junctional rhythm
c) Atrial fibrillation
d) Ventricular fibrillation
Answer: b) Junctional rhythm
Explanation: When the AV node takes over as the pacemaker, it results in a
junctional rhythm.
20. What is the key characteristic of ventricular fibrillation?
a) A regular heart rhythm
b) Rapid, disorganized electrical activity in the ventricles
c) Slower heart rates with strong contractions
d) Delayed repolarization
Answer: b) Rapid, disorganized electrical activity in the ventricles
Explanation: Ventricular fibrillation is a life-threatening condition where the
ventricles quiver instead of contracting.
Cardiac Dysrhythmias: Electrical Conduction System
Multiple Choice Test
1. What is the primary pacemaker of the heart?
a) Atrioventricular (AV) node
b) Sinoatrial (SA) node
c) Bundle of His
d) Purkinje fibers
Answer: b) Sinoatrial (SA) node
Explanation: The SA node is the primary pacemaker of the heart, initiating
the heartbeat.
2. What is the normal rate of automaticity for the SA node?
a) 40 – 60 bpm
b) 20 – 40 bpm
c) 60 – 100 bpm
d) 100 – 120 bpm
Answer: c) 60 – 100 bpm
Explanation: The SA node typically fires at a rate of 60 to 100 beats per
minute.
3. Where is the SA node located?
a) Right atrium
b) Left ventricle
c) Right ventricle
d) Left atrium
Answer: a) Right atrium
Explanation: The SA node is situated in the right atrium of the heart.
4. Which node is considered the secondary pacemaker of the heart?
a) Sinoatrial (SA) node
b) Atrioventricular (AV) node
c) Bundle of His
d) Purkinje fibers
Answer: b) Atrioventricular (AV) node
Explanation: The AV node acts as the secondary pacemaker when the SA
node fails.
5. What is the normal rate of automaticity for the Atrioventricular
(AV) node?
a) 60 – 100 bpm
b) 40 – 60 bpm
c) 20 – 40 bpm
d) 100 – 120 bpm
Answer: b) 40 – 60 bpm
Explanation: The AV node fires at a rate of 40 to 60 beats per minute.
6. What happens if both the SA and AV nodes fail to generate an
impulse?
,a) The atria stop contracting
b) The Bundle of His takes over
c) The Purkinje fibers take over as pacemaker
d) The heart ceases to function
Answer: c) The Purkinje fibers take over as pacemaker
Explanation: If both the SA and AV nodes fail, the Purkinje fibers act as a
last resort pacemaker with a rate of 20–40 bpm.
7. Which of the following has the fastest rate of automaticity?
a) SA node
b) AV node
c) Bundle of His
d) Purkinje fibers
Answer: a) SA node
Explanation: The SA node has the fastest intrinsic rate of automaticity,
between 60-100 bpm.
8. Which part of the heart's electrical conduction system has the
slowest intrinsic firing rate?
a) SA node
b) AV node
c) Purkinje fibers
d) Bundle of His
Answer: c) Purkinje fibers
Explanation: The Purkinje fibers fire at a rate of 20–40 bpm, the slowest in
the conduction system.
9. Which of the following describes the location and function of the
Bundle of His?
a) Located in the right atrium; primary pacemaker
b) Located between the atria and ventricles; conducts impulses to the
ventricles
c) Located in the ventricles; initiates contraction of the ventricles
d) Located in the left atrium; slows down the heart rate
Answer: b) Located between the atria and ventricles; conducts
impulses to the ventricles
Explanation: The Bundle of His transmits electrical impulses from the AV
node to the ventricles.
10. What role do the Purkinje fibers play in the heart's conduction
system?
a) They slow down the heart rate.
b) They initiate electrical impulses in the SA node.
c) They conduct electrical impulses to the ventricular myocardium, causing
contraction.
d) They generate electrical impulses that override the SA node.
Answer: c) They conduct electrical impulses to the ventricular
myocardium, causing contraction
Explanation: Purkinje fibers ensure that the ventricles contract in
coordination to pump blood effectively.
,11. Which part of the heart is most responsible for the delay in
electrical conduction, allowing the ventricles time to fill with blood?
a) SA node
b) AV node
c) Bundle of His
d) Purkinje fibers
Answer: b) AV node
Explanation: The AV node slows down the electrical impulse to allow the
ventricles time to fill before contraction.
12. What term is used to describe the heart's ability to generate its
own electrical impulses without external stimuli?
a) Contractility
b) Conductivity
c) Automaticity
d) Excitability
Answer: c) Automaticity
Explanation: Automaticity is the heart's ability to generate its own electrical
impulses.
13. What is the electrical charge inside the heart cells during the
resting phase?
a) Positive
b) Neutral
c) Negative
d) Alternating
Answer: c) Negative
Explanation: During the resting phase, the inside of heart cells is negatively
charged compared to the outside.
14. Which phase of the cardiac cycle involves the depolarization of
the ventricles, leading to their contraction?
a) Diastole
b) Repolarization
c) Systole
d) Resting potential
Answer: c) Systole
Explanation: Systole is when the ventricles depolarize and contract to pump
blood.
15. What is the refractory period in cardiac cells?
a) A period of fast depolarization
b) A period when cells are unable to respond to a new stimulus
c) The time when cells generate an action potential
d) The moment when cells fully repolarize
Answer: b) A period when cells are unable to respond to a new
stimulus
Explanation: The refractory period is the phase during which cardiac cells
cannot be excited by another impulse.
16. What happens during repolarization of the cardiac cells?
, a) Cells return to a resting state
b) Cells are unable to contract
c) Cells become depolarized again
d) Cells generate an action potential
Answer: a) Cells return to a resting state
Explanation: Repolarization restores the negative charge inside the cell,
allowing it to return to its resting state.
17. Which electrolyte is primarily responsible for the depolarization
of cardiac cells?
a) Sodium (Na⁺)
b) Potassium (K⁺)
c) Calcium (Ca²⁺)
d) Chloride (Cl⁻)
Answer: a) Sodium (Na⁺)
Explanation: Sodium ions enter the cell during depolarization, causing the
interior of the cell to become more positive.
18. What is the role of calcium (Ca²⁺) in the cardiac action potential?
a) Causes depolarization of the SA node
b) Stabilizes the cell membrane
c) Aids in repolarization
d) Initiates myocardial contraction
Answer: d) Initiates myocardial contraction
Explanation: Calcium ions are responsible for the contraction of myocardial
cells after depolarization.
19. Which dysrhythmia is most likely to occur when the electrical
conduction is initiated from the AV node instead of the SA node?
a) Sinus tachycardia
b) Junctional rhythm
c) Atrial fibrillation
d) Ventricular fibrillation
Answer: b) Junctional rhythm
Explanation: When the AV node takes over as the pacemaker, it results in a
junctional rhythm.
20. What is the key characteristic of ventricular fibrillation?
a) A regular heart rhythm
b) Rapid, disorganized electrical activity in the ventricles
c) Slower heart rates with strong contractions
d) Delayed repolarization
Answer: b) Rapid, disorganized electrical activity in the ventricles
Explanation: Ventricular fibrillation is a life-threatening condition where the
ventricles quiver instead of contracting.
