1.1.3 Structure and operation of the mammalian heart Quiz: Pearson Edexcel Biology A (Salters-Nuffield), Unit 1

The 20 questions

1. Which chamber of the mammalian heart has the thickest muscular wall?

   • The right ventricle, because it pumps blood to the lungs against the greatest resistance
   • The left ventricle, because it pumps blood at high pressure round the whole body
   • The right atrium, because it receives blood from the vena cava at the highest pressure
   • The left atrium, because it receives oxygenated blood from the pulmonary veins

2. What is the correct order of the phases of the cardiac cycle?

   • Ventricular systole, then atrial systole, then cardiac diastole
   • Atrial systole, then cardiac diastole, then ventricular systole
   • Cardiac diastole, then ventricular systole, then atrial systole
   • Atrial systole, then ventricular systole, then cardiac diastole

3. What is the function of the atrioventricular valves?

   • To prevent backflow of blood from the aorta into the left ventricle during diastole
   • To prevent backflow of blood from the ventricles into the atria when the ventricles contract
   • To stop blood entering the pulmonary artery from the right ventricle during atrial systole
   • To pump blood from the atria into the ventricles during the cardiac cycle

4. What causes the semilunar valves to close?

   • Blood pressure in the aorta or pulmonary artery pushes back on the cusps when ventricular pressure falls
   • The cusps are pulled shut by tendons attached to the papillary muscles during systole
   • Contraction of the atria pushes the valves shut so that blood cannot leave the ventricles
   • Blood flowing from the atria into the ventricles pushes the cusps against the artery walls

5. Which blood vessel carries deoxygenated blood from the right ventricle to the lungs?

   • Vena cava
   • Pulmonary artery
   • Pulmonary vein
   • Aorta

6. Which heart chamber receives oxygenated blood from the lungs?

   • Left atrium, via the pulmonary veins
   • Right ventricle, via the vena cava
   • Right atrium, via the pulmonary artery
   • Left ventricle, via the aorta

7. A heart beats at 75 beats per minute. What is the duration of one complete cardiac cycle?

   • 1.25 s
   • 0.075 s
   • 0.8 s
   • 75 s

8. A ventricle has a stroke volume of 70 cm^3 and the heart rate is 70 beats per minute. What is the cardiac output?

   • 4900 cm^3 per minute
   • 1000 cm^3 per minute
   • 70 cm^3 per minute
   • 140 cm^3 per minute

9. What causes the sound of the heart beat, the lub-dub sound?

   • The stretching of the aorta when blood is pumped out of the left ventricle at high pressure
   • The rush of blood through the open atria and the contraction of the atrial walls in the cardiac cycle
   • The closure of the atrioventricular valves at the start of systole, followed by the closure of the semilunar valves
   • The opening of the semilunar valves in diastole, which allows blood back into the ventricles

10. Why do the ventricles contract from the apex upwards?

    • This squeezes blood towards the exits of the ventricles, so it is pushed out efficiently
    • This makes the atria fill more quickly, so the atrioventricular valves open at the same time
    • This allows the cardiac muscle to relax before the atria contract, so the cycle is shorter
    • This stops blood from flowing back into the veins, which needs the apex to contract first

11. Where does the heart's own blood supply come from?

    • Pulmonary veins that carry blood from the lungs directly to the heart muscle
    • The vena cava, which supplies oxygenated blood directly to the right atrium
    • Coronary arteries branching from the aorta just above the semilunar valve
    • Capillaries in the lungs that diffuse oxygen into the heart muscle during diastole

12. Which of these explains why the atrioventricular node delays the signal before ventricular contraction?

    • It stops the impulse from reaching the ventricles, so the ventricles only respond to the atria
    • It increases the heart rate by sending a stronger signal to the sinoatrial node for each beat
    • It ensures the atria finish contracting before the ventricles begin, so blood is pushed fully into the ventricles
    • It makes the ventricles relax before the atria, so pressure in the atria falls before systole

13. In a heart with a heart rate of 60 beats per minute and a stroke volume of 75 cm^3, what is the cardiac output in dm^3 per minute?

    • 4.5 dm^3 per minute
    • 1.25 dm^3 per minute
    • 45 dm^3 per minute
    • 0.45 dm^3 per minute

14. Which statement about the mammalian heart's septum is correct?

    • It separates the oxygenated blood on the left from the deoxygenated blood on the right, preventing mixing
    • It separates the atria from the ventricles so that blood can only flow in one direction through the heart
    • It separates the pulmonary artery from the aorta so that the two vessels carry blood at equal pressure
    • It contains the sinoatrial node, which controls the rate at which the heart contracts

15. A student dissects a sheep's heart and finds the left ventricle wall is 12 mm thick and the right ventricle wall is 4 mm thick. What is the best explanation for this difference?

    • The left ventricle must generate a higher pressure to push blood round the systemic circulation
    • The right ventricle has more valves that need thicker walls to hold them in place during systole
    • The right ventricle pumps oxygenated blood, which requires a smaller wall to avoid excess oxygen loss
    • The left ventricle is responsible for filling the atria, which needs a stronger wall than the right

16. Which pressure change directly causes the atrioventricular valves to open during diastole?

    • Pulmonary artery pressure falls below atrial pressure during atrial systole
    • Ventricular pressure rises above aortic pressure as the ventricles contract
    • Atrial pressure rises above ventricular pressure as the ventricles relax and fill
    • Aortic pressure falls below atmospheric pressure as the ventricles finish contracting

17. Why is the heart described as myogenic?

    • Its contraction is initiated by the cardiac muscle itself, without needing nerve impulses to start each beat
    • It is controlled entirely by hormones released from the adrenal glands during each cardiac cycle
    • It contracts only when stimulated by skeletal muscle, which surrounds the heart and squeezes it
    • Its valves open and close by muscle contraction driven by the autonomic nervous system at each beat

18. During which phase of the cardiac cycle is blood pressure in the aorta highest?

    • Atrial diastole, just before the atrioventricular valves open
    • Ventricular systole, just after the semilunar valves open
    • Atrial systole, when the atria push blood into the ventricles
    • Cardiac diastole, when all four chambers are relaxed and filling

19. In an experiment, a heart is perfused and the rate of beating is changed by a drug. Which is the most valid conclusion if the stroke volume stays the same but the heart rate doubles?

    • Cardiac output quadruples, because stroke volume and heart rate both affect output multiplicatively
    • Cardiac output halves, because a faster rate means each beat must eject less blood
    • Cardiac output doubles, because cardiac output is the product of stroke volume and heart rate
    • Cardiac output stays the same, because stroke volume is the only factor that determines output

20. Which statement describes the role of the sinoatrial node?

    • It is the pacemaker that generates impulses which spread across the atria and set the heart rate
    • It is a coronary artery that supplies oxygenated blood to the pacemaker region of the heart
    • It is a valve that opens at the start of each cardiac cycle to let blood into the atria
    • It is a nerve that carries signals from the brain to the lungs to control the breathing rate

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