STRAIGHTERLINE A&P II QUIZ 2 2026/2027 | Complete
Solution with Verified Answers | Cardiovascular,
Lymphatic/Immune, Respiratory | Pass Guaranteed - A+
Graded
Domain 1: Cardiovascular System (20 Questions)
Q1: A 68-year-old patient presents with chest pain. An ECG shows a prolonged PR
interval (>0.20 seconds) with normal P waves and normal QRS complexes. Which
cardiac conduction abnormality is present, and where is the block located?
A. Bundle branch block at the Bundle of His
B. First-degree AV block at the AV node [CORRECT]
C. Ventricular fibrillation in the Purkinje fibers
D. Sinoatrial node exit block
Correct Answer: B
Rationale: First-degree AV block is characterized by a prolonged PR interval (>0.20
seconds or >5 small boxes on ECG) with maintained 1:1 conduction (every P wave
followed by QRS complex). The delay occurs at the AV node, where impulses from the
atria are slowed before reaching the ventricles. This is often benign and can occur in
athletes or with medications (beta-blockers, calcium channel blockers, digoxin), or with
increased vagal tone.
Option A is incorrect because bundle branch blocks cause widened QRS complexes
(>0.12 seconds), not PR prolongation. Option C is incorrect because ventricular
fibrillation shows chaotic electrical activity without identifiable P waves or QRS
complexes, not organized rhythm with prolonged PR. Option D is incorrect because SA
,node exit block would cause dropped P waves or pauses in atrial activity, not PR interval
prolongation.
Q2: During a cardiac cycle, which event causes the "lub" sound (S1) of the heart?
A. Closure of the semilunar valves (aortic and pulmonary)
B. Closure of the AV valves (mitral and tricuspid) at the beginning of systole [CORRECT]
C. Opening of the AV valves during ventricular filling
D. Turbulent blood flow through coronary arteries
Correct Answer: B
Rationale: The first heart sound (S1, "lub") is produced by the closure of the
atrioventricular (AV) valves—the mitral (bicuspid) and tricuspid valves—at the beginning
of ventricular systole. When ventricular pressure exceeds atrial pressure, these valves
close abruptly, creating vibrations audible as S1. This marks the onset of systole and
coincides with the QRS complex on ECG.
Option A is incorrect because semilunar valve closure produces the second heart sound
(S2, "dub") at the end of systole. Option C is incorrect because valve opening is generally
silent; heart sounds are produced by valve closure. Option D is incorrect because
coronary blood flow occurs during diastole and does not produce audible heart sounds.
Q3: A patient has a resting heart rate of 75 bpm and stroke volume of 70 mL/beat.
During exercise, heart rate increases to 150 bpm and stroke volume increases to 100
mL/beat. What is the percentage increase in cardiac output?
A. 100%
B. 186% [CORRECT]
C. 50%
D. 125%
,Correct Answer: B
Rationale: Cardiac output (CO) = Heart rate (HR) × Stroke volume (SV). Resting CO = 75
bpm × 70 mL/beat = 5,250 mL/min (5.25 L/min). Exercise CO = 150 bpm × 100 mL/beat
= 15,000 mL/min (15 L/min). Increase = 15,000 - 5,250 = 9,750 mL/min. Percentage
increase = (9,750 ÷ 5,250) × 100 = 186%. This demonstrates how both chronotropic
(HR) and inotropic (SV) effects combine to dramatically increase cardiac output during
exercise.
Option A (100%) only accounts for the doubling of heart rate. Option C (50%) and D
(125%) represent miscalculations of the combined effect.
Q4: Which layer of blood vessels contains smooth muscle and elastic fibers, allowing
for vasoconstriction and vasodilation?
A. Tunica intima (inner layer)
B. Tunica media (middle layer) [CORRECT]
C. Tunica adventitia (outer layer)
D. Tunica serosa (serous membrane)
Correct Answer: B
Rationale: The tunica media is the middle layer of blood vessel walls, composed
primarily of smooth muscle cells and elastic fibers. This layer is thickest in arteries
(especially elastic arteries like the aorta) and allows for: (1) Vasoconstriction (smooth
muscle contraction reducing vessel diameter) and vasodilation (smooth muscle
relaxation increasing diameter), regulating blood flow and pressure; (2) Elastic recoil in
large arteries maintaining continuous blood flow during diastole (Windkessel effect).
Option A is incorrect because the tunica intima consists of endothelium (simple
squamous epithelium) and subendothelial connective tissue; it lacks smooth muscle.
, Option C is incorrect because the tunica adventitia is outer connective tissue with
collagen and elastic fibers anchoring vessels, but lacks significant smooth muscle.
Option D is incorrect because tunica serosa is not a standard blood vessel layer; serous
membranes cover organs in body cavities.
Q5: A patient with hypertension has elevated afterload. Which statement best describes
afterload in cardiac physiology?
A. The volume of blood in ventricles at end-diastole
B. The resistance the ventricle must overcome to eject blood [CORRECT]
C. The intrinsic contractile force of the myocardium
D. The heart rate during systole
Correct Answer: B
Rationale: Afterload is the pressure or resistance that the ventricles must overcome to
eject blood during systole. It is primarily determined by: (1) Systemic vascular
resistance (arteriolar tone) for the left ventricle; (2) Pulmonary vascular resistance for
the right ventricle; (3) Aortic/pulmonary valve stenosis increases afterload. In
hypertension, elevated arterial pressure increases afterload, making the heart work
harder to eject stroke volume, leading to left ventricular hypertrophy over time.
Option A describes preload (end-diastolic volume, venous return). Option C describes
contractility (inotropic state, independent of preload/afterload). Option D describes
chronotropy, not afterload.
Q6: Which ECG wave represents ventricular depolarization, and what is its normal
duration?
A. P wave; 0.06-0.10 seconds
B. QRS complex; 0.06-0.10 seconds [CORRECT]
Solution with Verified Answers | Cardiovascular,
Lymphatic/Immune, Respiratory | Pass Guaranteed - A+
Graded
Domain 1: Cardiovascular System (20 Questions)
Q1: A 68-year-old patient presents with chest pain. An ECG shows a prolonged PR
interval (>0.20 seconds) with normal P waves and normal QRS complexes. Which
cardiac conduction abnormality is present, and where is the block located?
A. Bundle branch block at the Bundle of His
B. First-degree AV block at the AV node [CORRECT]
C. Ventricular fibrillation in the Purkinje fibers
D. Sinoatrial node exit block
Correct Answer: B
Rationale: First-degree AV block is characterized by a prolonged PR interval (>0.20
seconds or >5 small boxes on ECG) with maintained 1:1 conduction (every P wave
followed by QRS complex). The delay occurs at the AV node, where impulses from the
atria are slowed before reaching the ventricles. This is often benign and can occur in
athletes or with medications (beta-blockers, calcium channel blockers, digoxin), or with
increased vagal tone.
Option A is incorrect because bundle branch blocks cause widened QRS complexes
(>0.12 seconds), not PR prolongation. Option C is incorrect because ventricular
fibrillation shows chaotic electrical activity without identifiable P waves or QRS
complexes, not organized rhythm with prolonged PR. Option D is incorrect because SA
,node exit block would cause dropped P waves or pauses in atrial activity, not PR interval
prolongation.
Q2: During a cardiac cycle, which event causes the "lub" sound (S1) of the heart?
A. Closure of the semilunar valves (aortic and pulmonary)
B. Closure of the AV valves (mitral and tricuspid) at the beginning of systole [CORRECT]
C. Opening of the AV valves during ventricular filling
D. Turbulent blood flow through coronary arteries
Correct Answer: B
Rationale: The first heart sound (S1, "lub") is produced by the closure of the
atrioventricular (AV) valves—the mitral (bicuspid) and tricuspid valves—at the beginning
of ventricular systole. When ventricular pressure exceeds atrial pressure, these valves
close abruptly, creating vibrations audible as S1. This marks the onset of systole and
coincides with the QRS complex on ECG.
Option A is incorrect because semilunar valve closure produces the second heart sound
(S2, "dub") at the end of systole. Option C is incorrect because valve opening is generally
silent; heart sounds are produced by valve closure. Option D is incorrect because
coronary blood flow occurs during diastole and does not produce audible heart sounds.
Q3: A patient has a resting heart rate of 75 bpm and stroke volume of 70 mL/beat.
During exercise, heart rate increases to 150 bpm and stroke volume increases to 100
mL/beat. What is the percentage increase in cardiac output?
A. 100%
B. 186% [CORRECT]
C. 50%
D. 125%
,Correct Answer: B
Rationale: Cardiac output (CO) = Heart rate (HR) × Stroke volume (SV). Resting CO = 75
bpm × 70 mL/beat = 5,250 mL/min (5.25 L/min). Exercise CO = 150 bpm × 100 mL/beat
= 15,000 mL/min (15 L/min). Increase = 15,000 - 5,250 = 9,750 mL/min. Percentage
increase = (9,750 ÷ 5,250) × 100 = 186%. This demonstrates how both chronotropic
(HR) and inotropic (SV) effects combine to dramatically increase cardiac output during
exercise.
Option A (100%) only accounts for the doubling of heart rate. Option C (50%) and D
(125%) represent miscalculations of the combined effect.
Q4: Which layer of blood vessels contains smooth muscle and elastic fibers, allowing
for vasoconstriction and vasodilation?
A. Tunica intima (inner layer)
B. Tunica media (middle layer) [CORRECT]
C. Tunica adventitia (outer layer)
D. Tunica serosa (serous membrane)
Correct Answer: B
Rationale: The tunica media is the middle layer of blood vessel walls, composed
primarily of smooth muscle cells and elastic fibers. This layer is thickest in arteries
(especially elastic arteries like the aorta) and allows for: (1) Vasoconstriction (smooth
muscle contraction reducing vessel diameter) and vasodilation (smooth muscle
relaxation increasing diameter), regulating blood flow and pressure; (2) Elastic recoil in
large arteries maintaining continuous blood flow during diastole (Windkessel effect).
Option A is incorrect because the tunica intima consists of endothelium (simple
squamous epithelium) and subendothelial connective tissue; it lacks smooth muscle.
, Option C is incorrect because the tunica adventitia is outer connective tissue with
collagen and elastic fibers anchoring vessels, but lacks significant smooth muscle.
Option D is incorrect because tunica serosa is not a standard blood vessel layer; serous
membranes cover organs in body cavities.
Q5: A patient with hypertension has elevated afterload. Which statement best describes
afterload in cardiac physiology?
A. The volume of blood in ventricles at end-diastole
B. The resistance the ventricle must overcome to eject blood [CORRECT]
C. The intrinsic contractile force of the myocardium
D. The heart rate during systole
Correct Answer: B
Rationale: Afterload is the pressure or resistance that the ventricles must overcome to
eject blood during systole. It is primarily determined by: (1) Systemic vascular
resistance (arteriolar tone) for the left ventricle; (2) Pulmonary vascular resistance for
the right ventricle; (3) Aortic/pulmonary valve stenosis increases afterload. In
hypertension, elevated arterial pressure increases afterload, making the heart work
harder to eject stroke volume, leading to left ventricular hypertrophy over time.
Option A describes preload (end-diastolic volume, venous return). Option C describes
contractility (inotropic state, independent of preload/afterload). Option D describes
chronotropy, not afterload.
Q6: Which ECG wave represents ventricular depolarization, and what is its normal
duration?
A. P wave; 0.06-0.10 seconds
B. QRS complex; 0.06-0.10 seconds [CORRECT]
