Exam 2: BIOS255 / BIOS 255 Anatomy and Physiology III
with Lab
Latest Update 2026/2027 | Grade A | 100% Correct
Section 1: Cardiovascular System – Heart Anatomy and Physiology
Q1: Which of the following structures is unique to cardiac muscle tissue and directly accounts
for its synchronized contraction as a single functional syncytium?
A. Striated arrangements of actin and myosin filaments
B. Intercalated discs containing gap junctions and desmosomes. [CORRECT]
C. T-tubules that are larger in diameter than those in skeletal muscle
D. A high density of mitochondria filling the sarcoplasm
Correct Answer: B
Rationale: Intercalated discs are specialized junctions between cardiac muscle cells that contain
gap junctions (allowing rapid ion passage for synchronized depolarization) and desmosomes
(preventing cell separation during contraction). Striated banding and high mitochondrial density
are also features of cardiac muscle, but they relate to force generation and ATP production,
respectively, rather than structural synchronization. While cardiac T-tubules are larger, their
primary role is facilitating excitation-contraction coupling, not binding adjacent cells together.
Q2: [Labeling/Matching] Match the following cardiac structural descriptions to their correct
anatomical term:
Dense connective tissue ring providing electrical insulation between atria and ventricles
Irregular muscular ridges lining the ventricular walls
Muscular columns projecting from the atrial walls
Strong, collagenous cords anchoring AV valve cusps to papillary muscles
Options:
,A. 1-Fibrous skeleton; 2-Trabeculae carneae; 3-Pectinate muscles; 4-Chordae tendineae.
[CORRECT]
B. 1-Endomysium; 2-Papillary muscles; 3-Trabeculae carneae; 4-Chordae tendineae.
C. 1-Fibrous skeleton; 2-Pectinate muscles; 3-Trabeculae carneae; 4-Auricles.
D. 1-Pericardium; 2-Trabeculae carneae; 3-Pectinate muscles; 4-Chordae tendineae.
Correct Answer: A
Rationale: The fibrous skeleton anchors valve cusps, prevents overstretching, and electrically
isolates the atria from the ventricles. Trabeculae carneae are the irregular ridges found on the
ventricular inner surface, whereas pectinate muscles are the comb-like ridges specific to the atrial
walls (particularly the right atrium). Chordae tendineae connect the AV valve flaps to the
papillary muscles to prevent prolapse. The endomysium is a delicate connective tissue wrapping
individual cells, not a macroscopic structural ring, and the pericardium is the outer sac, not an
internal electrical insulator.
Q3: [Sequence Ordering] Place the following structures of the cardiac conduction system in the
correct anatomical sequence for the transmission of an action potential from the atria to the
ventricles:
Bundle branches (right and left)
Atrioventricular (AV) node
Sinoatrial (SA) node
Purkinje fibers
Atrioventricular (AV) bundle (Bundle of His)
A. 3, 2, 5, 1, 4. [CORRECT]
B. 3, 5, 2, 1, 4
C. 2, 3, 5, 4, 1
D. 3, 2, 1, 5, 4
Correct Answer: A
Rationale: The cardiac action potential originates at the SA node (3), travels across the atria to
the AV node (2), where it briefly delays to allow complete atrial contraction. It then passes into
the AV bundle/Bundle of His (5), descends through the interventricular septum via the right and
left bundle branches (1), and finally spreads to the ventricular myocardium via the Purkinje
, fibers (4). Option B incorrectly places the AV bundle before the AV node, and Options C and D
severely misorder the fundamental pathway.
Q4: During which phase of the cardiac cycle are the atrioventricular (AV) valves closed, the
semilunar (SL) valves closed, and the ventricular volume remaining constant?
A. Ventricular ejection
B. Isovolumetric contraction. [CORRECT]
C. Isovolumetric relaxation
D. Atrial systole
Correct Answer: B
Rationale: Isovolumetric contraction occurs immediately after the QRS complex when
ventricular pressure rises above atrial pressure (closing AV valves) but has not yet exceeded the
pressure in the aorta/pulmonary trunk (keeping SL valves closed). Because all valves are closed,
no blood can enter or exit, making the ventricular volume constant ("iso-volumetric"). Option C
also has constant volume, but it occurs when ventricular pressure drops below arterial pressure
and before AV valves open. Options A and D both involve valve opening and blood movement.
Q5: [Clinical Correlation] A 55-year-old male presents with severe crushing chest pain. Coronary
angiography reveals complete occlusion of the left anterior descending (LAD) artery. Which of
the following areas of the heart is most likely to suffer ischemic injury?
A. Right atrium and right ventricle
B. Left atrium and posterior left ventricle
C. Anterior interventricular septum and anterior walls of both ventricles. [CORRECT]
D. Lateral wall of the left ventricle only
Correct Answer: C
Rationale: The left anterior descending (LAD) artery, often called the "widow-maker," travels
down the anterior interventricular sulcus and supplies blood to the anterior interventricular
septum, the anterior walls of both ventricles, and the apex. The right coronary artery primarily
supplies the right atrium and ventricle (Option A). The circumflex artery supplies the lateral and
posterior left ventricle (Option D). The posterior interventricular artery (usually a branch of the
RCA) supplies the posterior septum (Option B).
with Lab
Latest Update 2026/2027 | Grade A | 100% Correct
Section 1: Cardiovascular System – Heart Anatomy and Physiology
Q1: Which of the following structures is unique to cardiac muscle tissue and directly accounts
for its synchronized contraction as a single functional syncytium?
A. Striated arrangements of actin and myosin filaments
B. Intercalated discs containing gap junctions and desmosomes. [CORRECT]
C. T-tubules that are larger in diameter than those in skeletal muscle
D. A high density of mitochondria filling the sarcoplasm
Correct Answer: B
Rationale: Intercalated discs are specialized junctions between cardiac muscle cells that contain
gap junctions (allowing rapid ion passage for synchronized depolarization) and desmosomes
(preventing cell separation during contraction). Striated banding and high mitochondrial density
are also features of cardiac muscle, but they relate to force generation and ATP production,
respectively, rather than structural synchronization. While cardiac T-tubules are larger, their
primary role is facilitating excitation-contraction coupling, not binding adjacent cells together.
Q2: [Labeling/Matching] Match the following cardiac structural descriptions to their correct
anatomical term:
Dense connective tissue ring providing electrical insulation between atria and ventricles
Irregular muscular ridges lining the ventricular walls
Muscular columns projecting from the atrial walls
Strong, collagenous cords anchoring AV valve cusps to papillary muscles
Options:
,A. 1-Fibrous skeleton; 2-Trabeculae carneae; 3-Pectinate muscles; 4-Chordae tendineae.
[CORRECT]
B. 1-Endomysium; 2-Papillary muscles; 3-Trabeculae carneae; 4-Chordae tendineae.
C. 1-Fibrous skeleton; 2-Pectinate muscles; 3-Trabeculae carneae; 4-Auricles.
D. 1-Pericardium; 2-Trabeculae carneae; 3-Pectinate muscles; 4-Chordae tendineae.
Correct Answer: A
Rationale: The fibrous skeleton anchors valve cusps, prevents overstretching, and electrically
isolates the atria from the ventricles. Trabeculae carneae are the irregular ridges found on the
ventricular inner surface, whereas pectinate muscles are the comb-like ridges specific to the atrial
walls (particularly the right atrium). Chordae tendineae connect the AV valve flaps to the
papillary muscles to prevent prolapse. The endomysium is a delicate connective tissue wrapping
individual cells, not a macroscopic structural ring, and the pericardium is the outer sac, not an
internal electrical insulator.
Q3: [Sequence Ordering] Place the following structures of the cardiac conduction system in the
correct anatomical sequence for the transmission of an action potential from the atria to the
ventricles:
Bundle branches (right and left)
Atrioventricular (AV) node
Sinoatrial (SA) node
Purkinje fibers
Atrioventricular (AV) bundle (Bundle of His)
A. 3, 2, 5, 1, 4. [CORRECT]
B. 3, 5, 2, 1, 4
C. 2, 3, 5, 4, 1
D. 3, 2, 1, 5, 4
Correct Answer: A
Rationale: The cardiac action potential originates at the SA node (3), travels across the atria to
the AV node (2), where it briefly delays to allow complete atrial contraction. It then passes into
the AV bundle/Bundle of His (5), descends through the interventricular septum via the right and
left bundle branches (1), and finally spreads to the ventricular myocardium via the Purkinje
, fibers (4). Option B incorrectly places the AV bundle before the AV node, and Options C and D
severely misorder the fundamental pathway.
Q4: During which phase of the cardiac cycle are the atrioventricular (AV) valves closed, the
semilunar (SL) valves closed, and the ventricular volume remaining constant?
A. Ventricular ejection
B. Isovolumetric contraction. [CORRECT]
C. Isovolumetric relaxation
D. Atrial systole
Correct Answer: B
Rationale: Isovolumetric contraction occurs immediately after the QRS complex when
ventricular pressure rises above atrial pressure (closing AV valves) but has not yet exceeded the
pressure in the aorta/pulmonary trunk (keeping SL valves closed). Because all valves are closed,
no blood can enter or exit, making the ventricular volume constant ("iso-volumetric"). Option C
also has constant volume, but it occurs when ventricular pressure drops below arterial pressure
and before AV valves open. Options A and D both involve valve opening and blood movement.
Q5: [Clinical Correlation] A 55-year-old male presents with severe crushing chest pain. Coronary
angiography reveals complete occlusion of the left anterior descending (LAD) artery. Which of
the following areas of the heart is most likely to suffer ischemic injury?
A. Right atrium and right ventricle
B. Left atrium and posterior left ventricle
C. Anterior interventricular septum and anterior walls of both ventricles. [CORRECT]
D. Lateral wall of the left ventricle only
Correct Answer: C
Rationale: The left anterior descending (LAD) artery, often called the "widow-maker," travels
down the anterior interventricular sulcus and supplies blood to the anterior interventricular
septum, the anterior walls of both ventricles, and the apex. The right coronary artery primarily
supplies the right atrium and ventricle (Option A). The circumflex artery supplies the lateral and
posterior left ventricle (Option D). The posterior interventricular artery (usually a branch of the
RCA) supplies the posterior septum (Option B).
