BIOS 252 | 250 EXAM REVISION MCQs
Questions ,Answers & rationales | latest
update
Here are 250 BIOS 252 MCQs covering Anatomy & Physiology II major topics:
Cardiovascular, Respiratory, Renal, Digestive, Endocrine, Reproductive, Nervous System,
Fluid/Electrolyte Balance, and Immunity
CARDIOVASCULAR SYSTEM (Questions 1–40)
1. Which layer of the heart wall is responsible for the contractile force of the heartbeat? A)
Epicardium B) Pericardium C) Myocardium (correct answer) D) Endocardium
Rationale: The myocardium is the thick muscular middle layer of the heart wall composed
of cardiac muscle cells responsible for generating the pumping force of the heart.
2. The sinoatrial (SA) node is located in which chamber of the heart? A) Left ventricle B) Left
atrium C) Right ventricle D) Right atrium (correct answer)
Rationale: The SA node, the primary pacemaker of the heart, is embedded in the posterior
wall of the right atrium near the opening of the superior vena cava.
3. Which of the following vessels carries oxygenated blood? A) Pulmonary artery B) Superior
vena cava C) Pulmonary vein (correct answer) D) Inferior vena cava
Rationale: The pulmonary veins are unique among veins in that they carry oxygenated
blood from the lungs back to the left atrium of the heart.
4. The normal resting cardiac output for an adult is approximately: A) 2–3 L/min B) 8–10 L/min
C) 4–6 L/min (correct answer) D) 10–12 L/min
,Rationale: Cardiac output = stroke volume × heart rate. At rest, with approximately 70 mL
stroke volume and 70 bpm, cardiac output averages 4.9 L/min, typically quoted as 4–6
L/min.
5. During ventricular systole, which valves are open? A) Mitral and tricuspid valves B) Aortic
and pulmonary valves (correct answer) C) All four valves D) Mitral and aortic valves
Rationale: During ventricular systole, the atrioventricular valves (mitral and tricuspid) are
closed while the semilunar valves (aortic and pulmonary) open to allow blood ejection into
the aorta and pulmonary trunk.
6. What is the Frank-Starling law of the heart? A) Heart rate increases as blood pressure rises B)
Stroke volume decreases as venous return increases C) The greater the stretch of cardiac
muscle, the greater the force of contraction (correct answer) D) Cardiac output is
independent of preload
Rationale: The Frank-Starling law states that within physiological limits, the heart pumps
all the blood it receives; greater venous return stretches the ventricles, increasing
contractile force and stroke volume.
7. Which ion is primarily responsible for the plateau phase (phase 2) of the cardiac action
potential? A) Sodium B) Potassium C) Calcium (correct answer) D) Chloride
Rationale: Phase 2 (plateau) of the cardiac action potential is maintained by slow inward
calcium current through L-type calcium channels, which also triggers calcium-induced
calcium release for muscle contraction.
8. Arteriosclerosis refers to: A) Inflammation of the pericardium B) Blockage of coronary
arteries by a clot C) Hardening and loss of elasticity of arterial walls (correct answer) D)
Dilation of veins due to incompetent valves
Rationale: Arteriosclerosis describes a group of diseases characterized by thickening,
hardening, and loss of elasticity of arterial walls, reducing blood flow and increasing risk of
hypertension and cardiovascular events.
,9. The QRS complex on an ECG represents: A) Atrial depolarization B) Ventricular
repolarization C) Ventricular depolarization (correct answer) D) Atrial repolarization
Rationale: The QRS complex represents the electrical depolarization spreading through
the ventricles, which triggers ventricular contraction (systole). Atrial repolarization is
hidden within the QRS complex.
10. Which of the following would increase heart rate? A) Increased parasympathetic stimulation
B) Increased sympathetic stimulation (correct answer) C) Elevated acetylcholine levels D)
Decreased epinephrine levels
Rationale: Sympathetic nervous system activation releases norepinephrine and
epinephrine, which bind to beta-1 adrenergic receptors on the SA node, increasing heart
rate (positive chronotropy).
11. Blood pressure is measured as: A) Diastolic over systolic B) Systolic over diastolic (correct
answer) C) Mean arterial pressure over pulse pressure D) Cardiac output over total peripheral
resistance
Rationale: Blood pressure is recorded as systolic pressure (ventricular contraction) over
diastolic pressure (ventricular relaxation). Normal is approximately 120/80 mmHg.
12. Which of the following is NOT a function of the lymphatic system in relation to the
cardiovascular system? A) Returns interstitial fluid to the blood B) Transports dietary fats C)
Plays a role in immunity D) Pumps blood through the systemic circuit (correct answer)
Rationale: The lymphatic system does not pump blood. Its functions include returning
excess interstitial fluid to the bloodstream, transporting dietary lipids as chylomicrons, and
housing immune cells.
13. Stroke volume is determined by: A) Heart rate alone B) Only afterload C) Preload,
contractility, and afterload (correct answer) D) Only preload
Rationale: Stroke volume is determined by three factors: preload (end-diastolic volume),
myocardial contractility (intrinsic force), and afterload (resistance the ventricle must
overcome to eject blood).
, 14. The atrioventricular (AV) node delays the electrical impulse to: A) Allow the SA node to
reset B) Prevent atrial fibrillation C) Allow the ventricles to fill completely before contracting
(correct answer) D) Increase conduction velocity in the Bundle of His
Rationale: The AV node imposes a delay of approximately 0.1 seconds, allowing complete
atrial contraction and ventricular filling before the impulse travels to the ventricles via the
Bundle of His.
15. Which type of blood vessel has the thickest tunica media? A) Veins B) Capillaries C)
Venules D) Arteries (correct answer)
Rationale: Arteries have the thickest tunica media rich in smooth muscle and elastic tissue,
allowing them to withstand high pressure generated during ventricular systole and
maintain blood pressure.
16. Vasoconstriction is primarily caused by: A) Parasympathetic stimulation B) Histamine
release C) Sympathetic stimulation via alpha-1 receptors (correct answer) D) Nitric oxide
release
Rationale: Sympathetic nerve fibers release norepinephrine, which binds to alpha-1
adrenergic receptors on vascular smooth muscle, causing vasoconstriction and increased
peripheral resistance.
17. The first heart sound (S1, "lub") is caused by: A) Opening of semilunar valves B) Closing of
semilunar valves C) Opening of AV valves D) Closing of AV valves (correct answer)
Rationale: S1 is produced by the sudden closure of the mitral and tricuspid (AV) valves at
the beginning of ventricular systole. S2 ("dub") is caused by closure of the aortic and
pulmonary semilunar valves.
18. Which of the following best describes the role of capillaries? A) Transport blood at high
pressure B) Return deoxygenated blood to the heart C) Store large volumes of blood D)
Exchange of gases, nutrients, and wastes between blood and tissues (correct answer)
Rationale: Capillaries are the functional exchange units of the cardiovascular system. Their
thin single-cell walls allow diffusion of oxygen, carbon dioxide, nutrients, and metabolic
waste products between blood and tissues.
Questions ,Answers & rationales | latest
update
Here are 250 BIOS 252 MCQs covering Anatomy & Physiology II major topics:
Cardiovascular, Respiratory, Renal, Digestive, Endocrine, Reproductive, Nervous System,
Fluid/Electrolyte Balance, and Immunity
CARDIOVASCULAR SYSTEM (Questions 1–40)
1. Which layer of the heart wall is responsible for the contractile force of the heartbeat? A)
Epicardium B) Pericardium C) Myocardium (correct answer) D) Endocardium
Rationale: The myocardium is the thick muscular middle layer of the heart wall composed
of cardiac muscle cells responsible for generating the pumping force of the heart.
2. The sinoatrial (SA) node is located in which chamber of the heart? A) Left ventricle B) Left
atrium C) Right ventricle D) Right atrium (correct answer)
Rationale: The SA node, the primary pacemaker of the heart, is embedded in the posterior
wall of the right atrium near the opening of the superior vena cava.
3. Which of the following vessels carries oxygenated blood? A) Pulmonary artery B) Superior
vena cava C) Pulmonary vein (correct answer) D) Inferior vena cava
Rationale: The pulmonary veins are unique among veins in that they carry oxygenated
blood from the lungs back to the left atrium of the heart.
4. The normal resting cardiac output for an adult is approximately: A) 2–3 L/min B) 8–10 L/min
C) 4–6 L/min (correct answer) D) 10–12 L/min
,Rationale: Cardiac output = stroke volume × heart rate. At rest, with approximately 70 mL
stroke volume and 70 bpm, cardiac output averages 4.9 L/min, typically quoted as 4–6
L/min.
5. During ventricular systole, which valves are open? A) Mitral and tricuspid valves B) Aortic
and pulmonary valves (correct answer) C) All four valves D) Mitral and aortic valves
Rationale: During ventricular systole, the atrioventricular valves (mitral and tricuspid) are
closed while the semilunar valves (aortic and pulmonary) open to allow blood ejection into
the aorta and pulmonary trunk.
6. What is the Frank-Starling law of the heart? A) Heart rate increases as blood pressure rises B)
Stroke volume decreases as venous return increases C) The greater the stretch of cardiac
muscle, the greater the force of contraction (correct answer) D) Cardiac output is
independent of preload
Rationale: The Frank-Starling law states that within physiological limits, the heart pumps
all the blood it receives; greater venous return stretches the ventricles, increasing
contractile force and stroke volume.
7. Which ion is primarily responsible for the plateau phase (phase 2) of the cardiac action
potential? A) Sodium B) Potassium C) Calcium (correct answer) D) Chloride
Rationale: Phase 2 (plateau) of the cardiac action potential is maintained by slow inward
calcium current through L-type calcium channels, which also triggers calcium-induced
calcium release for muscle contraction.
8. Arteriosclerosis refers to: A) Inflammation of the pericardium B) Blockage of coronary
arteries by a clot C) Hardening and loss of elasticity of arterial walls (correct answer) D)
Dilation of veins due to incompetent valves
Rationale: Arteriosclerosis describes a group of diseases characterized by thickening,
hardening, and loss of elasticity of arterial walls, reducing blood flow and increasing risk of
hypertension and cardiovascular events.
,9. The QRS complex on an ECG represents: A) Atrial depolarization B) Ventricular
repolarization C) Ventricular depolarization (correct answer) D) Atrial repolarization
Rationale: The QRS complex represents the electrical depolarization spreading through
the ventricles, which triggers ventricular contraction (systole). Atrial repolarization is
hidden within the QRS complex.
10. Which of the following would increase heart rate? A) Increased parasympathetic stimulation
B) Increased sympathetic stimulation (correct answer) C) Elevated acetylcholine levels D)
Decreased epinephrine levels
Rationale: Sympathetic nervous system activation releases norepinephrine and
epinephrine, which bind to beta-1 adrenergic receptors on the SA node, increasing heart
rate (positive chronotropy).
11. Blood pressure is measured as: A) Diastolic over systolic B) Systolic over diastolic (correct
answer) C) Mean arterial pressure over pulse pressure D) Cardiac output over total peripheral
resistance
Rationale: Blood pressure is recorded as systolic pressure (ventricular contraction) over
diastolic pressure (ventricular relaxation). Normal is approximately 120/80 mmHg.
12. Which of the following is NOT a function of the lymphatic system in relation to the
cardiovascular system? A) Returns interstitial fluid to the blood B) Transports dietary fats C)
Plays a role in immunity D) Pumps blood through the systemic circuit (correct answer)
Rationale: The lymphatic system does not pump blood. Its functions include returning
excess interstitial fluid to the bloodstream, transporting dietary lipids as chylomicrons, and
housing immune cells.
13. Stroke volume is determined by: A) Heart rate alone B) Only afterload C) Preload,
contractility, and afterload (correct answer) D) Only preload
Rationale: Stroke volume is determined by three factors: preload (end-diastolic volume),
myocardial contractility (intrinsic force), and afterload (resistance the ventricle must
overcome to eject blood).
, 14. The atrioventricular (AV) node delays the electrical impulse to: A) Allow the SA node to
reset B) Prevent atrial fibrillation C) Allow the ventricles to fill completely before contracting
(correct answer) D) Increase conduction velocity in the Bundle of His
Rationale: The AV node imposes a delay of approximately 0.1 seconds, allowing complete
atrial contraction and ventricular filling before the impulse travels to the ventricles via the
Bundle of His.
15. Which type of blood vessel has the thickest tunica media? A) Veins B) Capillaries C)
Venules D) Arteries (correct answer)
Rationale: Arteries have the thickest tunica media rich in smooth muscle and elastic tissue,
allowing them to withstand high pressure generated during ventricular systole and
maintain blood pressure.
16. Vasoconstriction is primarily caused by: A) Parasympathetic stimulation B) Histamine
release C) Sympathetic stimulation via alpha-1 receptors (correct answer) D) Nitric oxide
release
Rationale: Sympathetic nerve fibers release norepinephrine, which binds to alpha-1
adrenergic receptors on vascular smooth muscle, causing vasoconstriction and increased
peripheral resistance.
17. The first heart sound (S1, "lub") is caused by: A) Opening of semilunar valves B) Closing of
semilunar valves C) Opening of AV valves D) Closing of AV valves (correct answer)
Rationale: S1 is produced by the sudden closure of the mitral and tricuspid (AV) valves at
the beginning of ventricular systole. S2 ("dub") is caused by closure of the aortic and
pulmonary semilunar valves.
18. Which of the following best describes the role of capillaries? A) Transport blood at high
pressure B) Return deoxygenated blood to the heart C) Store large volumes of blood D)
Exchange of gases, nutrients, and wastes between blood and tissues (correct answer)
Rationale: Capillaries are the functional exchange units of the cardiovascular system. Their
thin single-cell walls allow diffusion of oxygen, carbon dioxide, nutrients, and metabolic
waste products between blood and tissues.
