1. 1
   A student dissected a mammalian heart and identified its four chambers, noticing clear differences in the thickness of their muscular walls. The student also identified a muscular wall separating the left and right sides of the heart.

   (a)

   A student dissected a mammalian heart and noticed that the wall of one chamber was much thicker and more muscular than the walls of the other three chambers. Which chamber did the student most likely observe?

   [1 mark]

   • ARight atrium
   • BLeft ventricle
   • CLeft atrium
   • DRight ventricle

   (b)

   What is the function of the muscular wall separating the left and right sides of the heart, identified by the student?

   [1 mark]

   • ATo prevent oxygenated and deoxygenated blood from mixing
   • BTo pump blood into the aorta
   • CTo generate electrical impulses that start the heartbeat
   • DTo filter blood before it enters the lungs

   (c)

   Explain why the wall of the left ventricle is much thicker and more muscular than the wall of the right ventricle.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A doctor listened to a patient's heart sounds using a stethoscope and heard two distinct sounds with each heartbeat, then measured the patient's pulse rate and asked them to do some light exercise to monitor changes in heart activity.

   (a)

   What mainly causes these heart sounds?

   [1 mark]

   • AThe closing of the heart valves
   • BThe contraction of the septum
   • CBlood flowing through the coronary arteries
   • DElectrical impulses from the pacemaker

   (b)

   After the patient exercised, the doctor noted an increase in heart rate. Which other method could the doctor use to directly monitor the electrical activity of the heart during this exercise?

   [1 mark]

   • AECG (electrocardiogram)
   • BMeasuring blood glucose concentration
   • CMeasuring body temperature
   • DTaking a blood smear

   (c)

   Explain why the patient's heart rate increased during exercise.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A patient was diagnosed with coronary heart disease after their coronary arteries became partly blocked by fatty deposits. The patient's doctor discussed risk factors and possible lifestyle changes to reduce further damage to the heart.

   (a)

   Explain why blockage of the coronary arteries can damage heart muscle tissue.

   [3 marks]

   (b)

   Discuss four risk factors that may have contributed to this patient's coronary heart disease, and explain how changes in diet and exercise could reduce the risk of further blockage.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A group of medical students used a mechanical model heart with clear plastic chambers to observe the opening and closing of its valves as fluid was pumped through in time with a simulated heartbeat.

   (a)

   Describe the sequence of events during one complete heartbeat, from the entry of blood into the atria to its ejection into the arteries, explaining the roles of the atrioventricular valves and the semilunar valves at each stage.

   [6 marks]

   (b)

   The students then damaged the atrioventricular valve on the left side of the model heart so that it did not close completely during ventricular contraction. Predict and explain the effects this would have on the pumping efficiency of the heart, and discuss why this defect would be more serious on the left side than an equivalent defect on the right side.

   [6 marks]

   Total for question 4: 12 marks

End of questions