Cardiovascular system quiz: 25 questions with answers

Questions and answers

By CanQuiz

An AI wrote the questions in this quiz from its creator’s material. It may contain mistakes.

1. 1.Which valve separates the left atrium from the left ventricle?

   • Tricuspid valve
   • Mitral (bicuspid) valve
   • Aortic valve
   • Pulmonary valve
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   Answer: Mitral (bicuspid) valve

   Explanation: The mitral valve, which has two cusps, guards the opening between the left atrium and the left ventricle. The tricuspid valve plays the same role on the right side of the heart.

2. 2.Which vessel carries oxygen-poor blood from the right ventricle towards the lungs?

   • Pulmonary veins
   • Aorta
   • Pulmonary trunk
   • Superior vena cava
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   Answer: Pulmonary trunk

   Explanation: The right ventricle ejects blood into the pulmonary trunk, which divides into the right and left pulmonary arteries. In the pulmonary circuit the arteries, not the veins, carry the oxygen-poor blood.

3. 3.Where does each normal heartbeat begin?

   • Atrioventricular node
   • Bundle of His
   • Purkinje fibres
   • Sinoatrial node
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   Answer: Sinoatrial node

   Explanation: The sinoatrial node in the wall of the right atrium depolarises spontaneously faster than any other cardiac tissue, so it sets the rhythm. This is why it is called the pacemaker of the heart.

4. 4.What is the main purpose of the brief conduction delay in the atrioventricular node?

   • It lets the atria finish contracting and topping up the ventricles before the ventricles contract
   • It gives the sinoatrial node time to repolarise
   • It stops blood flowing back into the venae cavae
   • It lets the coronary arteries fill before each beat
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   Answer: It lets the atria finish contracting and topping up the ventricles before the ventricles contract

   Explanation: The impulse slows down as it crosses the atrioventricular node. The pause means atrial contraction is complete, and the ventricles are full, before ventricular depolarisation starts.

5. 5.On a standard ECG, what does the QRS complex mainly represent?

   • Atrial depolarisation
   • Ventricular depolarisation
   • Ventricular repolarisation
   • Closure of the semilunar valves
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   Answer: Ventricular depolarisation

   Explanation: The QRS complex records the spread of depolarisation through the ventricles. The P wave reflects atrial depolarisation and the T wave ventricular repolarisation, while atrial repolarisation is usually hidden inside the QRS.

6. 6.What mainly produces the first heart sound (S1)?

   • Closure of the aortic and pulmonary valves
   • Opening of the mitral and tricuspid valves
   • Closure of the mitral and tricuspid valves
   • Blood rushing into the ventricles in early diastole
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   Answer: Closure of the mitral and tricuspid valves

   Explanation: S1 marks the start of ventricular systole, when rising ventricular pressure shuts the atrioventricular valves. The second sound, S2, comes from the closure of the semilunar valves at the end of systole.

7. 7.Which statement describes the isovolumetric contraction phase of the cardiac cycle?

   • The atrioventricular valves are open and the ventricles are filling
   • All four valves are closed and ventricular pressure is rising
   • The aortic valve is open and blood is leaving the left ventricle
   • All four valves are closed and ventricular pressure is falling
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   Answer: All four valves are closed and ventricular pressure is rising

   Explanation: Once the atrioventricular valves close, the ventricles contract with no outlet until their pressure exceeds that in the aorta and pulmonary trunk, so volume stays the same. Closed valves with falling pressure describe isovolumetric relaxation instead.

8. 8.Cardiac output is calculated as which of the following?

   • Stroke volume multiplied by mean arterial pressure
   • Heart rate multiplied by end-diastolic volume
   • Stroke volume divided by heart rate
   • Heart rate multiplied by stroke volume
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   Answer: Heart rate multiplied by stroke volume

   Explanation: Cardiac output is the volume pumped by one ventricle per minute. It equals the number of beats per minute times the volume ejected with each beat.

9. 9.According to the Frank-Starling mechanism, what happens when more blood returns to the ventricle during diastole?

   • The ventricle stretches more and contracts more forcefully, raising stroke volume
   • The sinoatrial node slows down to allow longer filling
   • The ventricle contracts less forcefully to protect its fibres
   • The aortic valve opens earlier in diastole
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   Answer: The ventricle stretches more and contracts more forcefully, raising stroke volume

   Explanation: A larger end-diastolic volume stretches the cardiac muscle fibres towards a more favourable overlap of actin and myosin. The stronger contraction that follows lets the heart match its output to venous return.

10. 10.Which vessels account for the largest share of total peripheral resistance?

    • The aorta
    • Large elastic arteries
    • Arterioles
    • Venules and veins
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    Answer: Arterioles

    Explanation: Arterioles have narrow lumens and thick smooth muscle that can change their radius. Because resistance rises steeply as radius falls, they are the main site where blood pressure drops and flow is regulated.

11. 11.At rest, where is most of the body's blood volume found?

    • Systemic arteries
    • Systemic veins and venules
    • Systemic capillaries
    • The chambers of the heart
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    Answer: Systemic veins and venules

    Explanation: Veins have thin, distensible walls and hold roughly two thirds of the blood at any moment. This is why they are described as capacitance or reservoir vessels.

12. 12.Which layer of the heart wall is made mainly of cardiac muscle?

    • Endocardium
    • Epicardium
    • Fibrous pericardium
    • Myocardium
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    Answer: Myocardium

    Explanation: The myocardium is the thick middle layer of contractile cardiac muscle cells. The endocardium lines the chambers and the epicardium covers the outer surface of the heart.

13. 13.What is the role of the chordae tendineae and papillary muscles?

    • They hold the semilunar valves closed during diastole
    • They stop the atrioventricular valve cusps from turning back into the atria during ventricular contraction
    • They anchor the heart to the diaphragm
    • They pump blood into the coronary arteries
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    Answer: They stop the atrioventricular valve cusps from turning back into the atria during ventricular contraction

    Explanation: The papillary muscles contract with the ventricle and tighten the chordae tendineae attached to the cusps of the mitral and tricuspid valves. This keeps the cusps from being pushed into the atria by the high ventricular pressure.

14. 14.Where do the right and left coronary arteries arise?

    • From the pulmonary trunk
    • From the arch of the aorta, beside the subclavian arteries
    • From the aortic sinuses of the ascending aorta, just above the aortic valve
    • Directly from the cavity of the left ventricle
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    Answer: From the aortic sinuses of the ascending aorta, just above the aortic valve

    Explanation: The coronary arteries are the first branches of the aorta, leaving it from the small dilations behind the cusps of the aortic valve. They supply the myocardium itself.

15. 15.Into which chamber does the coronary sinus drain?

    • Right atrium
    • Left atrium
    • Right ventricle
    • Left ventricle
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    Answer: Right atrium

    Explanation: The coronary sinus runs in the groove on the back of the heart, collects most of the venous blood from the myocardium, and opens into the right atrium.

16. 16.In the fetal heart, which two structures does the foramen ovale connect?

    • The pulmonary trunk and the aorta
    • The right atrium and the left atrium
    • The right ventricle and the left ventricle
    • The umbilical vein and the inferior vena cava
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    Answer: The right atrium and the left atrium

    Explanation: The foramen ovale lets much of the blood entering the right atrium pass straight to the left atrium, bypassing the fluid-filled fetal lungs. The pulmonary trunk and aorta are linked by a different shunt, the ductus arteriosus.

17. 17.What mainly sustains the plateau phase of the action potential in a ventricular muscle cell?

    • Influx of sodium through fast sodium channels
    • Influx of calcium through L-type calcium channels
    • Influx of chloride through ligand-gated channels
    • Efflux of sodium through the sodium-potassium pump
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    Answer: Influx of calcium through L-type calcium channels

    Explanation: During the plateau, calcium entering through L-type channels roughly balances potassium leaving the cell, so the membrane stays depolarised. The long plateau also gives a long refractory period, which prevents tetanic contraction of the heart.

18. 18.What is the effect of noradrenaline acting on beta-1 receptors in the heart?

    • Lower heart rate and weaker contraction
    • Lower heart rate with no change in contraction
    • Higher heart rate and stronger contraction
    • Constriction of the coronary arteries only
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    Answer: Higher heart rate and stronger contraction

    Explanation: Beta-1 stimulation speeds the firing of the sinoatrial node and increases calcium entry into cardiac muscle cells. The result is a faster heart rate and greater contractility.

19. 19.Which nerve carries the parasympathetic fibres that slow the heart?

    • Phrenic nerve
    • Glossopharyngeal nerve
    • Greater splanchnic nerve
    • Vagus nerve
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    Answer: Vagus nerve

    Explanation: Parasympathetic fibres reach the heart through the vagus nerve and release acetylcholine, mainly at the sinoatrial and atrioventricular nodes. This slows the heart rate and atrioventricular conduction.

20. 20.When arterial blood pressure rises suddenly, how does the baroreceptor reflex respond?

    • It increases vagal activity and reduces sympathetic activity, slowing the heart and dilating vessels
    • It increases sympathetic activity, speeding up the heart
    • It constricts the arterioles to raise resistance further
    • It stimulates the release of more noradrenaline from the adrenal medulla
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    Answer: It increases vagal activity and reduces sympathetic activity, slowing the heart and dilating vessels

    Explanation: Stretch receptors in the carotid sinus and aortic arch fire faster when pressure rises. The brainstem responds with more parasympathetic and less sympathetic output, which lowers heart rate, contractility and peripheral resistance.

21. 21.The pulmonary veins carry oxygen-rich blood to the left atrium.

    • True
    • False
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    Answer: True

    Explanation: Blood that has picked up oxygen in the lungs returns to the heart through the pulmonary veins, which open into the left atrium. They are the only veins in the adult that carry oxygen-rich blood.

22. 22.The wall of the right ventricle is thicker than the wall of the left ventricle.

    • True
    • False
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    Answer: False

    Explanation: The left ventricle has the thickest wall because it pumps blood against the much higher pressure of the systemic circulation. The right ventricle only has to push blood through the low-pressure pulmonary circuit.

23. 23.The cusps of the aortic and pulmonary valves are attached to chordae tendineae.

    • True
    • False
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    Answer: False

    Explanation: Only the atrioventricular valves have chordae tendineae. The semilunar valves close passively when blood flowing back fills their pocket-like cusps.

24. 24.The wall of a capillary is made of a single layer of endothelial cells resting on a basement membrane.

    • True
    • False
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    Answer: True

    Explanation: Capillaries lack the smooth muscle and connective tissue layers of larger vessels. Their thin wall keeps the distance short for exchange of gases, nutrients and wastes with the tissues.

25. 25.At rest, most ventricular filling happens passively, before the atria contract.

    • True
    • False
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    Answer: True

    Explanation: When the atrioventricular valves open, blood stored in the atria and veins flows into the relaxed ventricles. Atrial contraction at the end of diastole adds only the final part of the filling at rest.