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Advent Health EKG Newest Exam Preparation With
Complete Questions And Correct Answers With
Rationales Already Graded A+Brand New Version!!
1. The normal resting membrane potential of a ventricular myocardial
cell is approximately:
A) -90 mV
B) -70 mV
C) +30 mV
D) -55 mV
Answer: A) -90 mV
Rationale: Ventricular myocardial cells have a stable resting membrane
potential of approximately -90 mV, established primarily by the
permeability of the cell membrane to potassium ions. This negative
intracellular environment is crucial for the rapid depolarization phase
that characterizes these cells, distinguishing them from pacemaker cells
which have a less negative resting potential and exhibit automaticity.
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2. Which phase of the cardiac action potential is characterized by rapid
sodium influx and is responsible for the rapid upstroke of the QRS
complex?
A) Phase 0
B) Phase 1
C) Phase 2
D) Phase 3
Answer: A) Phase 0
Rationale: Phase 0 is the rapid depolarization phase mediated by the
opening of voltage-gated fast sodium channels, allowing a massive
influx of sodium ions into the cell. This influx shifts the membrane
potential from -90 mV toward +20 mV and corresponds to the QRS
complex on the surface electrocardiogram, representing ventricular
depolarization.
3. The plateau phase of the cardiac action potential, which
distinguishes cardiac muscle from skeletal muscle, is primarily due to:
A) Increased potassium efflux
B) Calcium influx through L-type calcium channels
C) Sodium-potassium ATPase activity
D) Chloride influx
Answer: B) Calcium influx through L-type calcium channels
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Rationale: Phase 2, the plateau phase, is maintained by a slow influx of
calcium ions through voltage-gated L-type calcium channels, which
balances the simultaneous outward potassium current. This plateau
prolongs the action potential and refractory period, preventing tetany
and allowing sufficient time for ventricular filling and coronary
perfusion.
4. The intrinsic rate of the sinoatrial node under normal autonomic
tone is approximately:
A) 40-60 beats per minute
B) 60-100 beats per minute
C) 100-150 beats per minute
D) 20-40 beats per minute
Answer: B) 60-100 beats per minute
Rationale: The sinoatrial node, the primary pacemaker of the heart,
exhibits intrinsic automaticity at a rate of 60-100 beats per minute in
the resting adult. This rate is modulated by autonomic nervous system
input, with parasympathetic tone typically slowing it toward the lower
end of this range and sympathetic stimulation accelerating it.
5. The atrioventricular node is located in which anatomical structure?
A) Interventricular septum
B) Crista terminalis
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C) Koch's triangle
D) Bundle of His
Answer: C) Koch's triangle
Rationale: The AV node is situated within Koch's triangle, an anatomical
region bounded by the coronary sinus ostium, the tendon of Todaro,
and the septal leaflet of the tricuspid valve. This location is critical for its
role in delaying conduction between the atria and ventricles, allowing
coordinated atrial contraction prior to ventricular systole.
6. The normal PR interval duration on a standard EKG is:
A) 0.12-0.20 seconds
B) 0.20-0.30 seconds
C) Less than 0.12 seconds
D) Greater than 0.22 seconds
Answer: A) 0.12-0.20 seconds
Rationale: The PR interval, measured from the onset of the P wave to
the onset of the QRS complex, represents the time required for atrial
depolarization and conduction through the AV node and His-Purkinje
system. Normal values range from 0.12 to 0.20 seconds (3 to 5 small
squares), with prolongation indicating first-degree AV block and
shortening suggesting pre-excitation syndromes.
7. The QRS complex duration in a normal EKG should not exceed:
Advent Health EKG Newest Exam Preparation With
Complete Questions And Correct Answers With
Rationales Already Graded A+Brand New Version!!
1. The normal resting membrane potential of a ventricular myocardial
cell is approximately:
A) -90 mV
B) -70 mV
C) +30 mV
D) -55 mV
Answer: A) -90 mV
Rationale: Ventricular myocardial cells have a stable resting membrane
potential of approximately -90 mV, established primarily by the
permeability of the cell membrane to potassium ions. This negative
intracellular environment is crucial for the rapid depolarization phase
that characterizes these cells, distinguishing them from pacemaker cells
which have a less negative resting potential and exhibit automaticity.
,2|Page
2. Which phase of the cardiac action potential is characterized by rapid
sodium influx and is responsible for the rapid upstroke of the QRS
complex?
A) Phase 0
B) Phase 1
C) Phase 2
D) Phase 3
Answer: A) Phase 0
Rationale: Phase 0 is the rapid depolarization phase mediated by the
opening of voltage-gated fast sodium channels, allowing a massive
influx of sodium ions into the cell. This influx shifts the membrane
potential from -90 mV toward +20 mV and corresponds to the QRS
complex on the surface electrocardiogram, representing ventricular
depolarization.
3. The plateau phase of the cardiac action potential, which
distinguishes cardiac muscle from skeletal muscle, is primarily due to:
A) Increased potassium efflux
B) Calcium influx through L-type calcium channels
C) Sodium-potassium ATPase activity
D) Chloride influx
Answer: B) Calcium influx through L-type calcium channels
,3|Page
Rationale: Phase 2, the plateau phase, is maintained by a slow influx of
calcium ions through voltage-gated L-type calcium channels, which
balances the simultaneous outward potassium current. This plateau
prolongs the action potential and refractory period, preventing tetany
and allowing sufficient time for ventricular filling and coronary
perfusion.
4. The intrinsic rate of the sinoatrial node under normal autonomic
tone is approximately:
A) 40-60 beats per minute
B) 60-100 beats per minute
C) 100-150 beats per minute
D) 20-40 beats per minute
Answer: B) 60-100 beats per minute
Rationale: The sinoatrial node, the primary pacemaker of the heart,
exhibits intrinsic automaticity at a rate of 60-100 beats per minute in
the resting adult. This rate is modulated by autonomic nervous system
input, with parasympathetic tone typically slowing it toward the lower
end of this range and sympathetic stimulation accelerating it.
5. The atrioventricular node is located in which anatomical structure?
A) Interventricular septum
B) Crista terminalis
, 4|Page
C) Koch's triangle
D) Bundle of His
Answer: C) Koch's triangle
Rationale: The AV node is situated within Koch's triangle, an anatomical
region bounded by the coronary sinus ostium, the tendon of Todaro,
and the septal leaflet of the tricuspid valve. This location is critical for its
role in delaying conduction between the atria and ventricles, allowing
coordinated atrial contraction prior to ventricular systole.
6. The normal PR interval duration on a standard EKG is:
A) 0.12-0.20 seconds
B) 0.20-0.30 seconds
C) Less than 0.12 seconds
D) Greater than 0.22 seconds
Answer: A) 0.12-0.20 seconds
Rationale: The PR interval, measured from the onset of the P wave to
the onset of the QRS complex, represents the time required for atrial
depolarization and conduction through the AV node and His-Purkinje
system. Normal values range from 0.12 to 0.20 seconds (3 to 5 small
squares), with prolongation indicating first-degree AV block and
shortening suggesting pre-excitation syndromes.
7. The QRS complex duration in a normal EKG should not exceed:
