1. 1
   A doctor is explaining the structure of the heart to a group of medical students using a dissected pig heart. She points out that the left ventricle wall is much thicker than the right ventricle wall. She also shows the students the valves inside the heart and explains that blood flows through the heart in only one direction, never backwards.

   (a)

   Both chambers pump the same volume of blood per beat. Which of these correctly explains why the left ventricle wall is thicker?

   [1 mark]

   • AThe left ventricle pumps blood at high pressure around the whole body, so it needs more muscle to generate that force
   • BThe left ventricle contains more blood than the right ventricle at any one time
   • CThe left ventricle is closer to the lungs so it must work harder against gravity
   • DThe left ventricle has more valves attached to its wall, requiring extra muscle for support

   (b)

   The doctor then points to a valve located between the left atrium and the left ventricle and asks the students what would happen if this valve failed to close properly during ventricular contraction. Which outcome is correct?

   [1 mark]

   • AOxygenated and deoxygenated blood would mix in the lungs instead of the heart
   • BBlood would flow from the right side of the heart directly into the left side
   • CThe heart rate would automatically increase to compensate for the pressure loss
   • DBlood would flow backwards from the ventricle into the atrium instead of being pumped into the aorta

   (c)

   The doctor also shows the students the aorta and the vena cava attached to the heart. Describe how the structure of the aorta is related to its function in the circulatory system.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   An athlete has a resting heart rate of 60 beats per minute and a stroke volume of 70 cm3. During a training session, her heart rate rises to 150 beats per minute and her stroke volume increases to 100 cm3. Her coach records these values to monitor her cardiovascular fitness over several months of training.

   (a)

   Using the equation cardiac output = stroke volume × heart rate, what is the athlete's resting cardiac output?

   [1 mark]

   • A130 cm3 per minute
   • B4200 cm3 per minute
   • C0.86 cm3 per minute
   • D420 cm3 per minute

   (b)

   After several months of training, the athlete's resting heart rate falls to 48 beats per minute, but her resting cardiac output stays roughly the same as before training. Which of these best explains this change?

   [1 mark]

   • AHer blood has become less dense, so it requires fewer heartbeats to circulate it
   • BHer heart has become smaller and more efficient, needing less blood overall
   • CHer stroke volume has increased, so fewer, stronger heartbeats are needed to pump the same volume of blood per minute
   • DHer lungs now supply more oxygen per breath, which directly lowers heart rate without changing stroke volume

   (c)

   Calculate the athlete's cardiac output during the training session described, when her heart rate is 150 beats per minute and her stroke volume is 100 cm3. Show your working and include units.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student is comparing three types of blood vessel taken from a mammal: one carries blood away from the heart at high pressure, one is a very narrow vessel with a wall only one cell thick, and one carries blood back towards the heart at low pressure and contains valves. She wants to relate the structure of each vessel to how it functions within the circulatory system.

   (a)

   Identify each of the three vessels and give one structural feature of each that matches its description.

   [3 marks]

   (b)

   Explain why the vessel carrying blood back to the heart at low pressure needs valves, while the vessel carrying blood away from the heart at high pressure does not rely on valves in the same way.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A patient has been diagnosed with a faulty valve between the left atrium and left ventricle, which allows blood to leak backwards into the atrium each time the ventricle contracts. The patient's doctor is considering whether the faulty valve should be surgically replaced and is explaining the risks and benefits of this decision to the patient.

   (a)

   Explain how this faulty valve would affect the efficiency of the circulatory system, referring to the structure and function of the heart in your answer.

   [6 marks]

   (b)

   The doctor explains that the faulty valve could be replaced with a mechanical valve or a biological valve taken from a pig heart. Discuss the factors the doctor and patient should consider when choosing between these two options.

   [6 marks]

   Total for question 4: 12 marks

End of questions