Q.1 Which chamber of the heart pumps oxygenated blood into the systemic circulation?
Right atrium
Right ventricle
Left atrium
Left ventricle
Explanation - The left ventricle pumps oxygenated blood into the aorta, which distributes it to the systemic circulation.
Correct answer is: Left ventricle
Q.2 The primary pacemaker of the heart is:
Atrioventricular (AV) node
Bundle of His
Purkinje fibers
Sinoatrial (SA) node
Explanation - The SA node generates spontaneous action potentials and sets the pace of the heartbeat.
Correct answer is: Sinoatrial (SA) node
Q.3 Which ion is primarily responsible for the plateau phase of the cardiac action potential?
Sodium (Na+)
Potassium (K+)
Calcium (Ca2+)
Chloride (Cl-)
Explanation - During the plateau phase, calcium influx through L-type calcium channels maintains depolarization.
Correct answer is: Calcium (Ca2+)
Q.4 During ventricular systole, which heart valves remain closed?
Aortic and pulmonary valves
Tricuspid and mitral valves
All four valves
None
Explanation - The atrioventricular valves (tricuspid and mitral) close during systole to prevent backflow into atria.
Correct answer is: Tricuspid and mitral valves
Q.5 What does the QRS complex in an ECG represent?
Atrial depolarization
Atrial repolarization
Ventricular depolarization
Ventricular repolarization
Explanation - The QRS complex corresponds to the rapid depolarization of the ventricles.
Correct answer is: Ventricular depolarization
Q.6 Which vessel carries oxygen-rich blood from the lungs to the heart?
Pulmonary artery
Pulmonary vein
Aorta
Superior vena cava
Explanation - Pulmonary veins carry oxygenated blood from the lungs to the left atrium.
Correct answer is: Pulmonary vein
Q.7 Stroke volume is defined as:
End-diastolic volume minus end-systolic volume
Heart rate times cardiac output
Cardiac output divided by heart rate
Blood pressure divided by heart rate
Explanation - Stroke volume is the amount of blood ejected per beat, calculated as EDV − ESV.
Correct answer is: End-diastolic volume minus end-systolic volume
Q.8 Which law states that stroke volume increases with increased venous return?
Poiseuille’s law
Laplace’s law
Frank-Starling law
Boyle’s law
Explanation - The Frank-Starling law explains that increased ventricular filling increases stroke volume due to optimal sarcomere stretching.
Correct answer is: Frank-Starling law
Q.9 Normal resting cardiac output in a healthy adult is approximately:
1 L/min
3 L/min
5 L/min
10 L/min
Explanation - At rest, an average adult’s cardiac output is around 5 liters per minute.
Correct answer is: 5 L/min
Q.10 Which factor primarily determines afterload?
Venous return
Systemic vascular resistance
Heart rate
End-diastolic volume
Explanation - Afterload is the resistance the ventricle must overcome, largely determined by systemic vascular resistance.
Correct answer is: Systemic vascular resistance
Q.11 What effect does the sympathetic nervous system have on heart rate?
Decreases heart rate
No effect
Increases heart rate
Stops the heart
Explanation - Sympathetic stimulation increases heart rate by enhancing SA node depolarization.
Correct answer is: Increases heart rate
Q.12 Which pressure drives coronary perfusion during diastole?
Left atrial pressure
Aortic pressure
Right atrial pressure
Pulmonary artery pressure
Explanation - Coronary arteries receive most of their blood flow during diastole, driven by aortic pressure.
Correct answer is: Aortic pressure
Q.13 Which vessel acts as a major resistance site in the circulation?
Aorta
Arterioles
Capillaries
Veins
Explanation - Arterioles are known as the resistance vessels because they regulate blood flow and systemic vascular resistance.
Correct answer is: Arterioles
Q.14 Baroreceptors that regulate blood pressure are located mainly in:
Aortic arch and carotid sinus
Left atrium and right atrium
Pulmonary artery and vena cava
Renal arteries
Explanation - Baroreceptors sense stretch in the arterial walls and help maintain blood pressure homeostasis.
Correct answer is: Aortic arch and carotid sinus
Q.15 Which ion is most responsible for the rapid depolarization phase of the cardiac action potential in ventricular myocytes?
Calcium (Ca2+)
Sodium (Na+)
Potassium (K+)
Magnesium (Mg2+)
Explanation - Rapid depolarization in ventricular myocytes occurs due to fast sodium influx.
Correct answer is: Sodium (Na+)
Q.16 Which heart sound corresponds to closure of the atrioventricular valves?
S1
S2
S3
S4
Explanation - The first heart sound (S1) is caused by closure of the mitral and tricuspid valves.
Correct answer is: S1
Q.17 What is the normal range of mean arterial pressure (MAP) in a healthy adult?
20–40 mmHg
40–60 mmHg
70–105 mmHg
120–150 mmHg
Explanation - Normal MAP ensures adequate perfusion of vital organs.
Correct answer is: 70–105 mmHg
Q.18 What is the primary determinant of diastolic blood pressure?
Cardiac output
Stroke volume
Systemic vascular resistance
Venous return
Explanation - Diastolic blood pressure reflects vascular resistance and arterial compliance.
Correct answer is: Systemic vascular resistance
Q.19 Which structure electrically connects atria to ventricles?
SA node
AV node
Purkinje fibers
Bundle of His
Explanation - The AV node is the only normal electrical pathway between atria and ventricles.
Correct answer is: AV node
Q.20 In the Wiggers diagram, the dicrotic notch corresponds to:
Opening of aortic valve
Closure of aortic valve
Mitral valve opening
Ventricular depolarization
Explanation - The dicrotic notch on the aortic pressure curve occurs due to elastic recoil after aortic valve closure.
Correct answer is: Closure of aortic valve
Q.21 What is the approximate ejection fraction in a normal healthy adult?
10–20%
30–40%
50–70%
80–90%
Explanation - Ejection fraction is normally around 50–70%, representing the fraction of blood ejected per beat.
Correct answer is: 50–70%
Q.22 Which structure delays electrical conduction to allow atrial contraction before ventricular contraction?
SA node
AV node
Purkinje fibers
Bundle branches
Explanation - The AV node slows conduction, allowing atria to contract before ventricles.
Correct answer is: AV node
Q.23 Venous return to the heart is facilitated by:
Respiratory pump
Skeletal muscle pump
Venous valves
All of the above
Explanation - Venous return is aided by respiratory movements, skeletal muscle contractions, and venous valves.
Correct answer is: All of the above
Q.24 Which blood vessel has the largest total cross-sectional area?
Aorta
Capillaries
Arterioles
Veins
Explanation - Capillaries collectively have the greatest cross-sectional area, allowing for efficient exchange.
Correct answer is: Capillaries
Q.25 Which neurotransmitter is released by parasympathetic fibers to the heart?
Norepinephrine
Dopamine
Acetylcholine
Epinephrine
Explanation - Parasympathetic fibers release acetylcholine, which reduces heart rate.
Correct answer is: Acetylcholine