Conduction System of the Heart Flashcards
Which of the following best describes the ability of cardiac cells to generate an electrical impulse without external stimulation?
A) Conductivity
B) Excitability
C) Automaticity
D) Depolarization
C) Automaticity
Rationale: Automaticity is the heart’s ability to generate electrical impulses independently, allowing contraction without requiring external nerve stimuli.
The sinoatrial (SA) node is responsible for initiating electrical impulses in the heart at what typical rate?
A) 40–60 bpm
B) 20–40 bpm
C) 60–100 bpm
D) 100–120 bpm
C) 60–100 bpm
Rationale: The SA node, located high in the right atrium, is the heart’s natural pacemaker, typically generating impulses at a rate of 60–100 bpm.
If the SA node fails, which structure can take over as the heart’s pacemaker?
A) Purkinje fibers
B) AV node
C) Right atrium
D) Bundle branches
B) AV node
Rationale: The AV node, located adjacent to the septum, can generate impulses at 40–60 bpm if the SA node fails.
The QRS complex on an electrocardiogram (EKG) represents which of the following?
A) Atrial depolarization
B) Ventricular depolarization
C) Ventricular repolarization
D) Atrial repolarization
B) Ventricular depolarization
Rationale: The QRS complex represents the electrical activity associated with ventricular depolarization, leading to ventricular contraction.
Which of the following effects describes a change in the strength of cardiac contraction?
A) Chronotropic
B) Inotropic
C) Dromotropic
D) Adrenergic
B) Inotropic
Rationale: The inotropic effect refers to the force of cardiac contraction. Chronotropic affects heart rate, and dromotropic influences electrical conduction speed.
Which wave on an electrocardiogram (EKG) represents ventricular repolarization?
A) P wave
B) QRS complex
C) T wave
D) U wave
C) T wave
Rationale: The T wave represents ventricular repolarization, where the ventricles recover and prepare for the next depolarization.
What is the primary function of baroreceptors in the cardiovascular system?
A) Detect changes in blood pressure
B) Detect changes in blood oxygen levels
C) Control sodium and potassium levels
D) Generate impulses to stimulate contraction
A) Detect changes in blood pressure
Rationale: Baroreceptors, located in the carotid arteries and aortic arch, sense blood pressure changes and help regulate cardiovascular function.
Which part of the conduction system has the slowest conduction speed to allow ventricular filling before contraction?
A) Sinoatrial (SA) node
B) Atrioventricular (AV) node
C) Purkinje fibers
D) Bundle branches
B) Atrioventricular (AV) node
Rationale: The AV node delays impulses to allow the ventricles to fully fill with blood before contraction occurs.
If a patient has an infarction that disrupts the Purkinje fibers, what direct effect would you expect on cardiac function?
A) Atrial contraction would stop
B) Ventricular contraction would be impaired
C) SA node function would cease
D) The patient would develop tachycardia
B) Ventricular contraction would be impaired
Rationale: The Purkinje fibers conduct impulses through the ventricles, so damage would lead to inefficient ventricular contractions.
Which of the following ions primarily influences depolarization in cardiac cells?
A) Sodium (Na+)
B) Potassium (K+)
C) Calcium (Ca2+)
D) Chloride (Cl-)
A) Sodium (Na+)
Rationale: Depolarization occurs when sodium rushes into the cardiac cells, generating the electrical impulse necessary for contraction.
Which of the following structures is responsible for initiating the electrical impulse in a normal heart rhythm?
A) Atrioventricular (AV) node
B) Sinoatrial (SA) node
C) Bundle of His
D) Purkinje fibers
B) Sinoatrial (SA) node
Rationale: The SA node (located in the right atrium) is the heart’s natural pacemaker, generating impulses at 60-100 bpm in normal sinus rhythm.
If the sinoatrial (SA) node fails, which structure takes over as the heart’s pacemaker?
A) Atrioventricular (AV) node
B) Bundle of His
C) Purkinje fibers
D) Ventricular myocardium
A) Atrioventricular (AV) node
Rationale: The AV node acts as the backup pacemaker, generating impulses at 40-60 bpm if the SA node fails.
What is the primary function of the atrioventricular (AV) node?
A) To directly stimulate ventricular contraction
B) To delay impulses from the SA node to allow ventricular filling
C) To generate an impulse when the Purkinje fibers fail
D) To increase the heart rate during sympathetic stimulation
B) To delay impulses from the SA node to allow ventricular filling
Rationale: The AV node delays conduction to ensure the atria contract fully before the ventricles, optimizing cardiac output.
Which of the following statements about the Purkinje fibers is correct?
A) They conduct impulses slowly to prevent ventricular tachycardia
B) They transmit electrical impulses to the ventricular myocardium
C) They initiate electrical impulses if the AV node fails
D) They depolarize the atria before the SA node does
B) They transmit electrical impulses to the ventricular myocardium
Rationale: The Purkinje fibers rapidly conduct impulses to the ventricular myocardium, ensuring coordinated contraction of the ventricles.
What does the T-wave represent on an electrocardiogram (EKG)?
A) Atrial depolarization
B) Ventricular depolarization
C) Atrial repolarization
D) Ventricular repolarization
D) Ventricular repolarization
Rationale: The T-wave represents ventricular repolarization, meaning the ventricles are recovering and preparing for the next contraction.
How can a myocardial infarction (MI) affect the cardiac conduction system?
A) It increases SA node firing rate, causing tachycardia
B) It can damage conduction pathways, leading to arrhythmias
C) It directly causes atrial fibrillation in all patients
D) It has no impact on the conduction system
B) It can damage conduction pathways, leading to arrhythmias
Rationale: An MI can cause ischemia in the conduction pathways, particularly affecting the SA node, AV node, or Purkinje fibers, leading to bradycardia, heart block, or ventricular arrhythmias.
Why might a patient with infective endocarditis develop a heart block?
A) The infection can damage the AV node, impairing conduction
B) The bacterial infection speeds up electrical impulses
C) The immune system blocks the SA node to fight infection
D) The Purkinje fibers become overactive, causing rapid conduction
A) The infection can damage the AV node, impairing conduction
Rationale: Infective endocarditis can cause valvular damage and inflammation that may extend to the AV node, leading to heart block and conduction delays.
How can an aortic aneurysm affect the heart’s electrical conduction?
A) It can compress the SA node, leading to sinus bradycardia
B) It can cause pressure on the AV node, leading to heart block
C) It stimulates the Purkinje fibers, leading to ventricular fibrillation
D) It directly affects ion exchange, leading to depolarization issues
B) It can cause pressure on the AV node, leading to heart block
Rationale: A thoracic aortic aneurysm can compress the AV node, causing conduction delays or complete heart block, which affects impulse transmission to the ventricles.
A patient with pericarditis is at risk for which conduction-related complication?
A) Atrial fibrillation
B) Ventricular tachycardia
C) Sinus arrest
D) Electrical alternans
D) Electrical alternans
Rationale: Pericarditis (inflammation of the pericardium) can cause pericardial effusion, leading to electrical alternans—a phenomenon where QRS complexes change in height due to the heart “swinging” in a fluid-filled pericardial sac.
How can myocardial ischemia from peripheral vascular disease (PVD) affect conduction?
A) It can lead to arrhythmias due to decreased oxygen supply to the heart
B) It causes hyperpolarization, making the heart resistant to impulses
C) It always results in atrial fibrillation
D) It has no effect on the heart’s electrical system
A) It can lead to arrhythmias due to decreased oxygen supply to the heart
Rationale: PVD can lead to poor circulation and ischemia, increasing the risk of conduction abnormalities like ventricular tachycardia, bradyarrhythmias, or heart blocks.
Which ECG finding is most concerning in a patient with a recent myocardial infarction?
A) Sinus tachycardia
B) A prolonged PR interval
C) ST-segment elevation
D) Isolated premature atrial contractions (PACs)
C) ST-segment elevation
Rationale: ST-segment elevation suggests acute myocardial injury, often due to a STEMI (ST-elevation myocardial infarction), which can affect electrical conduction and lead to life-threatening arrhythmias.
