BIOL 252 Module 3 Exam Review: 200
Ultimate Q&As with Rationales | Human
Anatomy & Physiology II
Question 1
,Which layer of the heart wall is composed of simple squamous epithelium and forms the
smooth inner lining of the chambers and valves?
A) Myocardium
B) Epicardium
C) Endocardium
D) Fibrous pericardium
ANSWER: C) Endocardium
EXPLANATION: The endocardium is the innermost layer of the heart wall. It consists of
an endothelium (simple squamous epithelium) and a thin layer of connective tissue,
providing a smooth surface that minimizes friction as blood flows through the heart
chambers.
Question 2
What structures prevent the atrioventricular (AV) valves from everting or flipping backward
into the atria during ventricular contraction?
A) Pectinate muscles
B) Chordae tendineae and papillary muscles
C) Trabeculae carneae
D) Semilunar cusps
ANSWER: B) Chordae tendineae and papillary muscles
EXPLANATION: The chordae tendineae (tendinous cords) anchor the cusps of the AV
valves to the papillary muscles projecting from the ventricular walls. When the ventricles
contract, the papillary muscles contract simultaneously, pulling the cords taut to hold the
valves shut against high pressure.
Question 3
Deoxygenated blood returning to the heart from the myocardium itself enters the right atrium
via which structure?
A) Superior vena cava
B) Inferior vena cava
C) Pulmonary trunk
D) Coronary sinus
ANSWER: D) Coronary sinus
EXPLANATION: The coronary sinus is a large venous channel on the posterior aspect of
,the heart that collects deoxygenated blood from the cardiac veins draining the myocardium
and empties it directly into the right atrium.
Question 4
Which component of the cardiac conduction system possesses the fastest intrinsic rate of
depolarization and serves as the primary pacemaker?
A) Sinoatrial (SA) node
B) Atrioventricular (AV) node
C) Atrioventricular (AV) bundle
D) Purkinje fibers
ANSWER: A) Sinoatrial (SA) node
EXPLANATION: The SA node, located in the superior wall of the right atrium, typically
depolarizes spontaneously at an intrinsic rate of 70–80 times per minute. Because this is
faster than any other autorhythmic region, it sets the sinus rhythm for the entire heart.
Question 5
Why is there a critical delay of approximately 0.1 seconds at the atrioventricular (AV) node?
A) To allow the ventricles to fully relax before filling
B) To allow the atria to complete their contraction and finish filling the ventricles
C) To allow the semilunar valves time to snap shut
D) To prevent the electrical signal from reaching the apex
ANSWER: B) To allow the atria to complete their contraction and finish filling the
ventricles
EXPLANATION: The AV node delay slows down the electrical impulse, ensuring that
atrial systole (contraction) is fully completed and the ventricles are optimally filled with
blood before ventricular systole begins.
Question 6
During which phase of the action potential in a cardiac contractile cell does a rapid influx of
extracellular sodium ions (\(Na^{+}\)) occur?
A) Phase 0 (Depolarization)
B) Phase 1 (Initial repolarization)
C) Phase 2 (Plateau)
D) Phase 3 (Rapid repolarization)
, ANSWER: A) Phase 0 (Depolarization)
EXPLANATION: Phase 0 is initiated by the opening of fast, voltage-gated sodium
channels. The massive influx of \(Na^{+}\) down its electrochemical gradient causes a
rapid reversal of membrane potential from negative to positive.
Question 7
The prolonged plateau phase (Phase 2) of a cardiac muscle action potential is unique
compared to skeletal muscle. Which ion channels are primarily responsible for maintaining
this plateau?
A) Fast voltage-gated \(Na^{+}\) channels
B) L-type voltage-gated \(Ca^{2+}\) channels
C) Chemically gated \(K^{+}\) channels
D) \(Na^{+}/K^{+}\) pumps
ANSWER: B) L-type voltage-gated \(Ca^{2+}\) channels
EXPLANATION: The plateau phase is maintained by a balance between the slow influx of
calcium ions (\(Ca^{2+}\)) through L-type channels and a slow efflux of potassium ions
(\(K^{+}\)). This prolonged depolarization creates a long absolute refractory period,
preventing tetanic contractions.
Question 8
On a standard electrocardiogram (ECG), which electrical event is hidden beneath the
prominent QRS complex?
A) Atrial depolarization
B) Ventricular repolarization
C) Atrial repolarization
D) Atrial systole
ANSWER: C) Atrial repolarization
EXPLANATION: Atrial repolarization occurs at the exact same time as ventricular
depolarization. Because the muscle mass of the ventricles is so much larger than that of
the atria, the electrical signals of ventricular depolarization (the QRS complex) completely
mask the signal of atrial repolarization.
Question 9
Ultimate Q&As with Rationales | Human
Anatomy & Physiology II
Question 1
,Which layer of the heart wall is composed of simple squamous epithelium and forms the
smooth inner lining of the chambers and valves?
A) Myocardium
B) Epicardium
C) Endocardium
D) Fibrous pericardium
ANSWER: C) Endocardium
EXPLANATION: The endocardium is the innermost layer of the heart wall. It consists of
an endothelium (simple squamous epithelium) and a thin layer of connective tissue,
providing a smooth surface that minimizes friction as blood flows through the heart
chambers.
Question 2
What structures prevent the atrioventricular (AV) valves from everting or flipping backward
into the atria during ventricular contraction?
A) Pectinate muscles
B) Chordae tendineae and papillary muscles
C) Trabeculae carneae
D) Semilunar cusps
ANSWER: B) Chordae tendineae and papillary muscles
EXPLANATION: The chordae tendineae (tendinous cords) anchor the cusps of the AV
valves to the papillary muscles projecting from the ventricular walls. When the ventricles
contract, the papillary muscles contract simultaneously, pulling the cords taut to hold the
valves shut against high pressure.
Question 3
Deoxygenated blood returning to the heart from the myocardium itself enters the right atrium
via which structure?
A) Superior vena cava
B) Inferior vena cava
C) Pulmonary trunk
D) Coronary sinus
ANSWER: D) Coronary sinus
EXPLANATION: The coronary sinus is a large venous channel on the posterior aspect of
,the heart that collects deoxygenated blood from the cardiac veins draining the myocardium
and empties it directly into the right atrium.
Question 4
Which component of the cardiac conduction system possesses the fastest intrinsic rate of
depolarization and serves as the primary pacemaker?
A) Sinoatrial (SA) node
B) Atrioventricular (AV) node
C) Atrioventricular (AV) bundle
D) Purkinje fibers
ANSWER: A) Sinoatrial (SA) node
EXPLANATION: The SA node, located in the superior wall of the right atrium, typically
depolarizes spontaneously at an intrinsic rate of 70–80 times per minute. Because this is
faster than any other autorhythmic region, it sets the sinus rhythm for the entire heart.
Question 5
Why is there a critical delay of approximately 0.1 seconds at the atrioventricular (AV) node?
A) To allow the ventricles to fully relax before filling
B) To allow the atria to complete their contraction and finish filling the ventricles
C) To allow the semilunar valves time to snap shut
D) To prevent the electrical signal from reaching the apex
ANSWER: B) To allow the atria to complete their contraction and finish filling the
ventricles
EXPLANATION: The AV node delay slows down the electrical impulse, ensuring that
atrial systole (contraction) is fully completed and the ventricles are optimally filled with
blood before ventricular systole begins.
Question 6
During which phase of the action potential in a cardiac contractile cell does a rapid influx of
extracellular sodium ions (\(Na^{+}\)) occur?
A) Phase 0 (Depolarization)
B) Phase 1 (Initial repolarization)
C) Phase 2 (Plateau)
D) Phase 3 (Rapid repolarization)
, ANSWER: A) Phase 0 (Depolarization)
EXPLANATION: Phase 0 is initiated by the opening of fast, voltage-gated sodium
channels. The massive influx of \(Na^{+}\) down its electrochemical gradient causes a
rapid reversal of membrane potential from negative to positive.
Question 7
The prolonged plateau phase (Phase 2) of a cardiac muscle action potential is unique
compared to skeletal muscle. Which ion channels are primarily responsible for maintaining
this plateau?
A) Fast voltage-gated \(Na^{+}\) channels
B) L-type voltage-gated \(Ca^{2+}\) channels
C) Chemically gated \(K^{+}\) channels
D) \(Na^{+}/K^{+}\) pumps
ANSWER: B) L-type voltage-gated \(Ca^{2+}\) channels
EXPLANATION: The plateau phase is maintained by a balance between the slow influx of
calcium ions (\(Ca^{2+}\)) through L-type channels and a slow efflux of potassium ions
(\(K^{+}\)). This prolonged depolarization creates a long absolute refractory period,
preventing tetanic contractions.
Question 8
On a standard electrocardiogram (ECG), which electrical event is hidden beneath the
prominent QRS complex?
A) Atrial depolarization
B) Ventricular repolarization
C) Atrial repolarization
D) Atrial systole
ANSWER: C) Atrial repolarization
EXPLANATION: Atrial repolarization occurs at the exact same time as ventricular
depolarization. Because the muscle mass of the ventricles is so much larger than that of
the atria, the electrical signals of ventricular depolarization (the QRS complex) completely
mask the signal of atrial repolarization.
Question 9
