IBHRE CCDS EXAMINATION - COMPLETE PRACTICE
QUESTIONS AND CORRECT ANSWERS WITH
DETAILED RATIONALES
SECTION 1: CARDIAC ANATOMY & ELECTROPHYSIOLOGY (Questions 1-50)
Question 1
Which structure initiates the electrical impulse in the normal heart?
A) Atrioventricular node
B) Bundle of His
C) Sinoatrial node
D) Purkinje fibers
Answer: C
Rationale: The sinoatrial (SA) node, located in the right atrial wall near the
superior vena cava, generates the heart's intrinsic rhythm in over 90% of
individuals. It functions as the primary pacemaker of the heart.
Question 2
Which ion is most responsible for the rapid depolarization phase (Phase 0) of
the cardiac action potential?
A) Calcium
B) Potassium
C) Sodium
,D) Chloride
Answer: C
Rationale: Phase 0 rapid depolarization is caused by a rapid influx of sodium
ions through voltage-gated sodium channels. This fast inward sodium current
is responsible for the upstroke of the action potential in working myocardial
cells.
Question 3
The AV node is primarily responsible for:
A) Generating the primary heart rate
B) Delaying conduction to allow ventricular filling
C) Rapidly conducting impulses to the ventricles
D) Depolarizing the ventricular myocardium
Answer: B
Rationale: The AV node provides a physiological delay (approximately 120-
200 ms) in impulse conduction, allowing time for atrial contraction to
complete ventricular filling before ventricular depolarization occurs.
Question 4
Purkinje fibers are specialized for:
A) Generating pacemaker impulses
B) Rapid conduction of electrical impulses through the ventricles
C) Filtering electrical signals
D) Storing calcium ions
,Answer: B
Rationale: Purkinje fibers are large-diameter conducting cells that rapidly
transmit electrical impulses from the bundle branches to the ventricular
myocardium, ensuring synchronized ventricular contraction.
Question 5
The normal resting membrane potential of a cardiac myocyte is
approximately:
A) -30 mV
B) -50 mV
C) -70 mV
D) -90 mV
Answer: D
Rationale: The normal resting membrane potential of ventricular myocytes is
approximately -90 mV, maintained primarily by the outward movement of
potassium ions through inward rectifier potassium channels.
Question 6
Phase 3 of the cardiac action potential is characterized by:
A) Rapid sodium influx
B) Calcium influx
C) Repolarization due to potassium efflux
D) Plateau phase
Answer: C
, Rationale: Phase 3 (rapid repolarization) is caused by potassium efflux
through rapid delayed rectifier potassium channels (Ikr), returning the
membrane potential toward the resting level.
Question 7
The bundle of His is located in the:
A) Right atrium
B) Interventricular septum
C) Left atrium
D) Pulmonary trunk
Answer: B
Rationale: The bundle of His originates at the AV node and travels through the
interventricular septum before dividing into the right and left bundle
branches.
Question 8
Bachmann's bundle connects which structures?
A) Right and left atria
B) Atria and ventricles
C) SA node and AV node
D) Right and left ventricles
Answer: A
Rationale: Bachmann's bundle (interatrial bundle) provides a preferential
conduction pathway between the right and left atria, facilitating synchronous
atrial depolarization.
QUESTIONS AND CORRECT ANSWERS WITH
DETAILED RATIONALES
SECTION 1: CARDIAC ANATOMY & ELECTROPHYSIOLOGY (Questions 1-50)
Question 1
Which structure initiates the electrical impulse in the normal heart?
A) Atrioventricular node
B) Bundle of His
C) Sinoatrial node
D) Purkinje fibers
Answer: C
Rationale: The sinoatrial (SA) node, located in the right atrial wall near the
superior vena cava, generates the heart's intrinsic rhythm in over 90% of
individuals. It functions as the primary pacemaker of the heart.
Question 2
Which ion is most responsible for the rapid depolarization phase (Phase 0) of
the cardiac action potential?
A) Calcium
B) Potassium
C) Sodium
,D) Chloride
Answer: C
Rationale: Phase 0 rapid depolarization is caused by a rapid influx of sodium
ions through voltage-gated sodium channels. This fast inward sodium current
is responsible for the upstroke of the action potential in working myocardial
cells.
Question 3
The AV node is primarily responsible for:
A) Generating the primary heart rate
B) Delaying conduction to allow ventricular filling
C) Rapidly conducting impulses to the ventricles
D) Depolarizing the ventricular myocardium
Answer: B
Rationale: The AV node provides a physiological delay (approximately 120-
200 ms) in impulse conduction, allowing time for atrial contraction to
complete ventricular filling before ventricular depolarization occurs.
Question 4
Purkinje fibers are specialized for:
A) Generating pacemaker impulses
B) Rapid conduction of electrical impulses through the ventricles
C) Filtering electrical signals
D) Storing calcium ions
,Answer: B
Rationale: Purkinje fibers are large-diameter conducting cells that rapidly
transmit electrical impulses from the bundle branches to the ventricular
myocardium, ensuring synchronized ventricular contraction.
Question 5
The normal resting membrane potential of a cardiac myocyte is
approximately:
A) -30 mV
B) -50 mV
C) -70 mV
D) -90 mV
Answer: D
Rationale: The normal resting membrane potential of ventricular myocytes is
approximately -90 mV, maintained primarily by the outward movement of
potassium ions through inward rectifier potassium channels.
Question 6
Phase 3 of the cardiac action potential is characterized by:
A) Rapid sodium influx
B) Calcium influx
C) Repolarization due to potassium efflux
D) Plateau phase
Answer: C
, Rationale: Phase 3 (rapid repolarization) is caused by potassium efflux
through rapid delayed rectifier potassium channels (Ikr), returning the
membrane potential toward the resting level.
Question 7
The bundle of His is located in the:
A) Right atrium
B) Interventricular septum
C) Left atrium
D) Pulmonary trunk
Answer: B
Rationale: The bundle of His originates at the AV node and travels through the
interventricular septum before dividing into the right and left bundle
branches.
Question 8
Bachmann's bundle connects which structures?
A) Right and left atria
B) Atria and ventricles
C) SA node and AV node
D) Right and left ventricles
Answer: A
Rationale: Bachmann's bundle (interatrial bundle) provides a preferential
conduction pathway between the right and left atria, facilitating synchronous
atrial depolarization.
