BAYCARE EKG TEST ACTUAL 2026/2027 | Electrocardiogram
Interpretation & Cardiac Rhythm Analysis | Correct Solutions
| Pass Guaranteed - A+ Graded
Section 1: Cardiac Anatomy & Electrophysiology (Q1-12)
Q1. The sinoatrial (SA) node is the primary pacemaker of the heart with an intrinsic
firing rate of:
A. 40-60 beats per minute
B. 60-100 beats per minute
C. 20-40 beats per minute
D. 100-150 beats per minute
Correct Answer: B. 60-100 beats per minute [CORRECT]
Rationale: The SA node is the primary pacemaker with an intrinsic rate of 60-100 bpm;
the AV junction fires at 40-60 bpm and Purkinje fibers at 20-40 bpm per AHA cardiac
conduction physiology.
Q2. The normal delay at the atrioventricular (AV) node allows time for ventricular filling
and corresponds to which portion of the EKG?
A. The QRS complex
B. The ST segment
C. The PR interval
D. The QT interval
Correct Answer: C. The PR interval [CORRECT]
Rationale: The PR interval (0.12-0.20 seconds) represents conduction from the SA node
through the AV node, allowing atrial kick and ventricular filling before ventricular
depolarization.
Q3. During Phase 0 of the cardiac action potential, rapid depolarization occurs primarily
due to:
A. Calcium influx through L-type channels
B. Potassium efflux through delayed rectifier channels
,C. Fast sodium influx through voltage-gated channels
D. Chloride influx through ligand-gated channels
Correct Answer: C. Fast sodium influx through voltage-gated channels [CORRECT]
Rationale: Phase 0 depolarization is mediated by fast voltage-gated sodium channel
opening; calcium influx characterizes Phase 2 plateau and potassium efflux
characterizes Phase 3 repolarization.
Q4. The plateau phase (Phase 2) of the cardiac action potential is characterized by:
A. Rapid potassium efflux and membrane repolarization
B. Calcium influx balancing potassium efflux, maintaining a positive membrane
potential
C. Sodium channel inactivation and resting potential restoration
D. Slow diastolic depolarization in pacemaker cells
Correct Answer: B. Calcium influx balancing potassium efflux, maintaining a positive
membrane potential [CORRECT]
Rationale: Phase 2 plateau is sustained by L-type calcium influx counteracting
potassium efflux, creating the characteristic flat segment before rapid repolarization in
Phase 3.
Q5. A patient receives a stimulus during the absolute refractory period. The expected
response is:
A. A premature ventricular contraction
B. No response due to inactivated sodium channels
C. A triggered arrhythmia from early afterdepolarizations
D. A normal but delayed depolarization
Correct Answer: B. No response due to inactivated sodium channels [CORRECT]
Rationale: During the absolute refractory period, voltage-gated sodium channels are
inactivated and no stimulus, regardless of strength, can elicit a new action potential,
preventing tetanic contraction of cardiac muscle.
Q6. A 68-year-old patient experiences acute chest pain and anxiety. Increased
sympathetic stimulation releases norepinephrine, producing which cardiac effect?
,A. Decreased heart rate and increased PR interval
B. Increased heart rate and increased contractility
C. Decreased conduction velocity through the AV node
D. Prolonged absolute refractory period
Correct Answer: B. Increased heart rate and increased contractility [CORRECT]
Rationale: Sympathetic stimulation via norepinephrine binding to beta-1 adrenergic
receptors increases chronotropy (rate), inotropy (contractility), and dromotropy
(conduction velocity), opposite to parasympathetic acetylcholine effects.
Q7. A patient receiving vagal nerve stimulation for refractory epilepsy develops a heart
rate of 52 bpm. This bradycardia results from:
A. Beta-1 receptor blockade at the SA node
B. Acetylcholine release increasing potassium permeability and decreasing SA node
firing
C. Norepinephrine depletion from sympathetic nerve terminals
D. Calcium channel inhibition at the AV node
Correct Answer: B. Acetylcholine release increasing potassium permeability and
decreasing SA node firing [CORRECT]
Rationale: Parasympathetic stimulation releases acetylcholine, which increases
potassium permeability (IKACh channels) and hyperpolarizes the SA node, slowing the
rate of Phase 4 diastolic depolarization and decreasing heart rate per AHA
electrophysiology.
Q8. The intrinsic firing rate of the Purkinje fiber network, which serves as the ventricular
escape pacemaker, is:
A. 60-100 beats per minute
B. 40-60 beats per minute
C. 20-40 beats per minute
D. 100-250 beats per minute
Correct Answer: C. 20-40 beats per minute [CORRECT]
, Rationale: Purkinje fibers have an intrinsic escape rate of 20-40 bpm; this slow rate
becomes clinically relevant in third-degree AV block when ventricular escape rhythms
originate from the Purkinje network.
Q9. During Phase 3 of the cardiac action potential, rapid repolarization returns the
membrane potential to resting levels primarily through:
A. Closure of sodium channels and opening of calcium channels
B. Efflux of potassium ions through delayed rectifier channels
C. Influx of chloride ions through voltage-gated channels
D. Reuptake of calcium into the sarcoplasmic reticulum alone
Correct Answer: B. Efflux of potassium ions through delayed rectifier channels
[CORRECT]
Rationale: Phase 3 rapid repolarization is driven by voltage-gated potassium channel
opening (IKr and IKs delayed rectifiers), causing potassium efflux that restores the
negative resting membrane potential toward Phase 4.
Q10. A patient with autonomic dysfunction has lost parasympathetic tone but maintains
sympathetic innervation. The expected resting EKG finding is:
A. Sinus bradycardia with first-degree AV block
B. Sinus tachycardia with shortened PR interval
C. Junctional escape rhythm at 40 bpm
D. Atrial fibrillation with slow ventricular response
Correct Answer: B. Sinus tachycardia with shortened PR interval [CORRECT]
Rationale: Loss of parasympathetic (vagal) tone removes the brake on SA node firing
and AV nodal conduction, resulting in unopposed sympathetic activity producing sinus
tachycardia and faster AV conduction per AHA autonomic physiology.
Q11. In the cardiac conduction system, an impulse travels from the SA node to the AV
node via the:
A. Bundle of His and right bundle branch
B. Internodal pathways and interatrial tracts
C. Purkinje fiber network
D. Left bundle branch and fascicles
Interpretation & Cardiac Rhythm Analysis | Correct Solutions
| Pass Guaranteed - A+ Graded
Section 1: Cardiac Anatomy & Electrophysiology (Q1-12)
Q1. The sinoatrial (SA) node is the primary pacemaker of the heart with an intrinsic
firing rate of:
A. 40-60 beats per minute
B. 60-100 beats per minute
C. 20-40 beats per minute
D. 100-150 beats per minute
Correct Answer: B. 60-100 beats per minute [CORRECT]
Rationale: The SA node is the primary pacemaker with an intrinsic rate of 60-100 bpm;
the AV junction fires at 40-60 bpm and Purkinje fibers at 20-40 bpm per AHA cardiac
conduction physiology.
Q2. The normal delay at the atrioventricular (AV) node allows time for ventricular filling
and corresponds to which portion of the EKG?
A. The QRS complex
B. The ST segment
C. The PR interval
D. The QT interval
Correct Answer: C. The PR interval [CORRECT]
Rationale: The PR interval (0.12-0.20 seconds) represents conduction from the SA node
through the AV node, allowing atrial kick and ventricular filling before ventricular
depolarization.
Q3. During Phase 0 of the cardiac action potential, rapid depolarization occurs primarily
due to:
A. Calcium influx through L-type channels
B. Potassium efflux through delayed rectifier channels
,C. Fast sodium influx through voltage-gated channels
D. Chloride influx through ligand-gated channels
Correct Answer: C. Fast sodium influx through voltage-gated channels [CORRECT]
Rationale: Phase 0 depolarization is mediated by fast voltage-gated sodium channel
opening; calcium influx characterizes Phase 2 plateau and potassium efflux
characterizes Phase 3 repolarization.
Q4. The plateau phase (Phase 2) of the cardiac action potential is characterized by:
A. Rapid potassium efflux and membrane repolarization
B. Calcium influx balancing potassium efflux, maintaining a positive membrane
potential
C. Sodium channel inactivation and resting potential restoration
D. Slow diastolic depolarization in pacemaker cells
Correct Answer: B. Calcium influx balancing potassium efflux, maintaining a positive
membrane potential [CORRECT]
Rationale: Phase 2 plateau is sustained by L-type calcium influx counteracting
potassium efflux, creating the characteristic flat segment before rapid repolarization in
Phase 3.
Q5. A patient receives a stimulus during the absolute refractory period. The expected
response is:
A. A premature ventricular contraction
B. No response due to inactivated sodium channels
C. A triggered arrhythmia from early afterdepolarizations
D. A normal but delayed depolarization
Correct Answer: B. No response due to inactivated sodium channels [CORRECT]
Rationale: During the absolute refractory period, voltage-gated sodium channels are
inactivated and no stimulus, regardless of strength, can elicit a new action potential,
preventing tetanic contraction of cardiac muscle.
Q6. A 68-year-old patient experiences acute chest pain and anxiety. Increased
sympathetic stimulation releases norepinephrine, producing which cardiac effect?
,A. Decreased heart rate and increased PR interval
B. Increased heart rate and increased contractility
C. Decreased conduction velocity through the AV node
D. Prolonged absolute refractory period
Correct Answer: B. Increased heart rate and increased contractility [CORRECT]
Rationale: Sympathetic stimulation via norepinephrine binding to beta-1 adrenergic
receptors increases chronotropy (rate), inotropy (contractility), and dromotropy
(conduction velocity), opposite to parasympathetic acetylcholine effects.
Q7. A patient receiving vagal nerve stimulation for refractory epilepsy develops a heart
rate of 52 bpm. This bradycardia results from:
A. Beta-1 receptor blockade at the SA node
B. Acetylcholine release increasing potassium permeability and decreasing SA node
firing
C. Norepinephrine depletion from sympathetic nerve terminals
D. Calcium channel inhibition at the AV node
Correct Answer: B. Acetylcholine release increasing potassium permeability and
decreasing SA node firing [CORRECT]
Rationale: Parasympathetic stimulation releases acetylcholine, which increases
potassium permeability (IKACh channels) and hyperpolarizes the SA node, slowing the
rate of Phase 4 diastolic depolarization and decreasing heart rate per AHA
electrophysiology.
Q8. The intrinsic firing rate of the Purkinje fiber network, which serves as the ventricular
escape pacemaker, is:
A. 60-100 beats per minute
B. 40-60 beats per minute
C. 20-40 beats per minute
D. 100-250 beats per minute
Correct Answer: C. 20-40 beats per minute [CORRECT]
, Rationale: Purkinje fibers have an intrinsic escape rate of 20-40 bpm; this slow rate
becomes clinically relevant in third-degree AV block when ventricular escape rhythms
originate from the Purkinje network.
Q9. During Phase 3 of the cardiac action potential, rapid repolarization returns the
membrane potential to resting levels primarily through:
A. Closure of sodium channels and opening of calcium channels
B. Efflux of potassium ions through delayed rectifier channels
C. Influx of chloride ions through voltage-gated channels
D. Reuptake of calcium into the sarcoplasmic reticulum alone
Correct Answer: B. Efflux of potassium ions through delayed rectifier channels
[CORRECT]
Rationale: Phase 3 rapid repolarization is driven by voltage-gated potassium channel
opening (IKr and IKs delayed rectifiers), causing potassium efflux that restores the
negative resting membrane potential toward Phase 4.
Q10. A patient with autonomic dysfunction has lost parasympathetic tone but maintains
sympathetic innervation. The expected resting EKG finding is:
A. Sinus bradycardia with first-degree AV block
B. Sinus tachycardia with shortened PR interval
C. Junctional escape rhythm at 40 bpm
D. Atrial fibrillation with slow ventricular response
Correct Answer: B. Sinus tachycardia with shortened PR interval [CORRECT]
Rationale: Loss of parasympathetic (vagal) tone removes the brake on SA node firing
and AV nodal conduction, resulting in unopposed sympathetic activity producing sinus
tachycardia and faster AV conduction per AHA autonomic physiology.
Q11. In the cardiac conduction system, an impulse travels from the SA node to the AV
node via the:
A. Bundle of His and right bundle branch
B. Internodal pathways and interatrial tracts
C. Purkinje fiber network
D. Left bundle branch and fascicles
