BIOL 271/BIOL271 Modules 5 & 6 Exam Actual
2026/2027 with Detailed Rationales | 100% Verified | Pass
Guaranteed
SECTION 1: CARDIOVASCULAR SYSTEM – HEART & VESSELS
(Questions 1–20)
Q1: The left ventricle has a thicker myocardial wall than the right ventricle primarily
because the left ventricle:
A. Pumps blood through the pulmonary circuit only
B. Must generate higher pressure to pump blood through the systemic circuit
C. Receives blood directly from the pulmonary veins
D. Has a smaller chamber volume
Correct Answer: B
Rationale: Correct because the left ventricle must generate systemic pressure
(approximately 120 mmHg) to pump blood through the high-resistance systemic circuit,
whereas the right ventricle generates only 25 mmHg for the low-resistance pulmonary
circuit; this functional demand produces the thicker wall.
Q2: During the cardiac cycle, the period when the ventricles are contracting and all
valves are closed is known as:
A. Isovolumetric relaxation
,B. Isovolumetric contraction
C. Ventricular ejection
D. Atrial systole
Correct Answer: B
Rationale: Correct because isovolumetric contraction is the brief phase when ventricular
pressure rises after the AV valves close but before the semilunar valves open;
ventricular volume remains constant while pressure increases rapidly.
Q3: The sinoatrial (SA) node is located in the:
A. Interventricular septum near the apex
B. Posterior wall of the left atrium
C. Posterior wall of the right atrium near the superior vena cava opening
D. Anterior wall of the right ventricle
Correct Answer: C
Rationale: Correct because the SA node is located in the posterior wall of the right
atrium near the opening of the superior vena cava; it serves as the normal pacemaker of
the heart with an intrinsic firing rate of 60–100 beats per minute.
Q4: On a standard ECG tracing, the QRS complex represents:
A. Atrial depolarization
B. Atrial repolarization
,C. Ventricular depolarization
D. Ventricular repolarization
Correct Answer: C
Rationale: Correct because the QRS complex represents ventricular depolarization; the
electrical signal spreads rapidly through the bundle of His, bundle branches, and
Purkinje fibers, causing coordinated ventricular contraction.
Q5: Stroke volume is defined as:
A. The volume of blood ejected by both ventricles in one minute
B. The volume of blood ejected by one ventricle during a single contraction
C. The total volume of blood in the circulatory system
D. The volume of blood remaining in the ventricle at end-systole
Correct Answer: B
Rationale: Correct because stroke volume is the volume of blood ejected by one
ventricle during a single contraction, normally 60–80 mL; cardiac output equals stroke
volume multiplied by heart rate.
Q6: The Frank-Starling law of the heart states that:
A. Heart rate is inversely proportional to stroke volume
B. Stroke volume increases as end-diastolic volume increases, up to a physiological
limit
, C. Blood pressure is directly proportional to peripheral resistance only
D. Cardiac output remains constant regardless of venous return
Correct Answer: B
Rationale: Correct because the Frank-Starling mechanism describes the intrinsic ability
of the heart to adjust stroke volume in response to changes in preload; greater
ventricular stretch from increased end-diastolic volume produces a more forceful
contraction.
Q7: Which blood vessel layer contains smooth muscle and elastic fibers that allow for
vasoconstriction and vasodilation?
A. Tunica intima
B. Tunica media
C. Tunica externa
D. Tunica adventitia
Correct Answer: B
Rationale: Correct because the tunica media is the middle layer containing circular
smooth muscle and elastic fibers; contraction and relaxation of this layer regulate
vessel diameter, blood pressure, and blood flow distribution.
Q8: The aortic semilunar valve opens when:
A. Atrial pressure exceeds ventricular pressure
B. Ventricular pressure exceeds aortic pressure
2026/2027 with Detailed Rationales | 100% Verified | Pass
Guaranteed
SECTION 1: CARDIOVASCULAR SYSTEM – HEART & VESSELS
(Questions 1–20)
Q1: The left ventricle has a thicker myocardial wall than the right ventricle primarily
because the left ventricle:
A. Pumps blood through the pulmonary circuit only
B. Must generate higher pressure to pump blood through the systemic circuit
C. Receives blood directly from the pulmonary veins
D. Has a smaller chamber volume
Correct Answer: B
Rationale: Correct because the left ventricle must generate systemic pressure
(approximately 120 mmHg) to pump blood through the high-resistance systemic circuit,
whereas the right ventricle generates only 25 mmHg for the low-resistance pulmonary
circuit; this functional demand produces the thicker wall.
Q2: During the cardiac cycle, the period when the ventricles are contracting and all
valves are closed is known as:
A. Isovolumetric relaxation
,B. Isovolumetric contraction
C. Ventricular ejection
D. Atrial systole
Correct Answer: B
Rationale: Correct because isovolumetric contraction is the brief phase when ventricular
pressure rises after the AV valves close but before the semilunar valves open;
ventricular volume remains constant while pressure increases rapidly.
Q3: The sinoatrial (SA) node is located in the:
A. Interventricular septum near the apex
B. Posterior wall of the left atrium
C. Posterior wall of the right atrium near the superior vena cava opening
D. Anterior wall of the right ventricle
Correct Answer: C
Rationale: Correct because the SA node is located in the posterior wall of the right
atrium near the opening of the superior vena cava; it serves as the normal pacemaker of
the heart with an intrinsic firing rate of 60–100 beats per minute.
Q4: On a standard ECG tracing, the QRS complex represents:
A. Atrial depolarization
B. Atrial repolarization
,C. Ventricular depolarization
D. Ventricular repolarization
Correct Answer: C
Rationale: Correct because the QRS complex represents ventricular depolarization; the
electrical signal spreads rapidly through the bundle of His, bundle branches, and
Purkinje fibers, causing coordinated ventricular contraction.
Q5: Stroke volume is defined as:
A. The volume of blood ejected by both ventricles in one minute
B. The volume of blood ejected by one ventricle during a single contraction
C. The total volume of blood in the circulatory system
D. The volume of blood remaining in the ventricle at end-systole
Correct Answer: B
Rationale: Correct because stroke volume is the volume of blood ejected by one
ventricle during a single contraction, normally 60–80 mL; cardiac output equals stroke
volume multiplied by heart rate.
Q6: The Frank-Starling law of the heart states that:
A. Heart rate is inversely proportional to stroke volume
B. Stroke volume increases as end-diastolic volume increases, up to a physiological
limit
, C. Blood pressure is directly proportional to peripheral resistance only
D. Cardiac output remains constant regardless of venous return
Correct Answer: B
Rationale: Correct because the Frank-Starling mechanism describes the intrinsic ability
of the heart to adjust stroke volume in response to changes in preload; greater
ventricular stretch from increased end-diastolic volume produces a more forceful
contraction.
Q7: Which blood vessel layer contains smooth muscle and elastic fibers that allow for
vasoconstriction and vasodilation?
A. Tunica intima
B. Tunica media
C. Tunica externa
D. Tunica adventitia
Correct Answer: B
Rationale: Correct because the tunica media is the middle layer containing circular
smooth muscle and elastic fibers; contraction and relaxation of this layer regulate
vessel diameter, blood pressure, and blood flow distribution.
Q8: The aortic semilunar valve opens when:
A. Atrial pressure exceeds ventricular pressure
B. Ventricular pressure exceeds aortic pressure
