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Figure 3 shows pressure and blood flow during the cardiac cycle in a dog - AQA - A-Level Biology - Question 3 - 2020 - Paper 1
Question 3
Figure 3 shows pressure and blood flow during the cardiac cycle in a dog. At P on Figure 3, the pressure in the left ventricle is increasing. At this time, the rate... show full transcript
Worked Solution & Example Answer:Figure 3 shows pressure and blood flow during the cardiac cycle in a dog - AQA - A-Level Biology - Question 3 - 2020 - Paper 1
Step 1
At P on Figure 3, the pressure in the left ventricle is increasing. At this time, the rate of blood flow has not yet started to increase in the aorta. Use evidence from Figure 3 to explain why.
Answer
At point P, the aortic valve is closed, meaning that blood from the left ventricle cannot enter the aorta. The pressure in the left ventricle rises as it contracts, but because the aortic pressure is higher at this moment, blood flow into the aorta does not commence. This results in an increase in left ventricular pressure without a corresponding increase in blood flow.
Step 2
At Q on Figure 3 there is a small increase in pressure and in rate of blood flow in the aorta. Explain how this happens and its importance.
Answer
At point Q, the aortic valve opens due to the pressure in the left ventricle exceeding that in the aorta, allowing blood to flow into the aorta. This increase in blood flow is crucial as it ensures oxygen-rich blood is delivered to the body. Additionally, the elastic recoil of the aorta helps to smooth the flow.
Step 3
A student correctly plotted the right ventricle pressure on the same grid as the left ventricle pressure in Figure 3. Describe one way in which the student’s curve would be similar to and one way it would be different from the curve shown in Figure 3.
Answer
Similarity: The pressure in the right ventricle would rise and fall in a similar pattern as the left ventricular pressure due to similar cardiac cycles.
Difference: The right ventricle pressure would be lower than the left ventricle pressure, as the right ventricle pumps blood to the lungs at a lower pressure compared to the systemic circulation.
Step 4