AQA AS Level Biology Paper 2, June 2023: Question 4

7 marks · Medium difficulty · Practical Techniques & Data Analysis

Identify cardiac structures in the correct sequence, describe changes in cardiac output based on a bar chart during different exercise intensities, and explain how arterioles control blood flow.

Practise this question

Question

The question contains three parts about the heart and blood flow. Part 04.1 features Table 2 listing various heart structures and vessels where students must order the flow of blood into and through the heart up to the left ventricle using numbers 1 to 6, with 'Left ventricle' already marked as 4. Part 04.2 presents a bar chart (Figure 2) showing the mean volume of the left ventricle before and after contraction alongside heart rate at rest, medium-intensity exercise, and high-intensity exercise, asking students to describe what causes the increase in cardiac output between rest and medium-intensity exercise, and between medium and high-intensity exercise. Part 04.3 asks for the name of the blood vessel that controls blood flow to muscles and an explanation of how these blood vessels change blood flow during exercise.
Question text

04.1 This question is about the flow of blood into and through the heart.

Add the numbers 1 to 6 to Table 2 to give the order of structures through which blood

will pass as it enters the heart and flows through the left ventricle.

Use each number only once. Number 4 has been done for you.

[2 marks]

Table 2

Aorta Pulmonary vein

Left atrioventricular valve Left semi-lunar valve

Right atrioventricular valve Vena cava

Left atrium Left ventricle 4

Right atrium Right ventricle

Pulmonary artery 10 Right semi-lunar valve

04.2 Scientists investigated the heart activity of humans at rest, during medium-intensity

exercise and during high-intensity exercise.

Figure 2 shows the scientists’ results.

Figure 2

Stroke volume = volume of blood leaving a ventricle with each contraction

Cardiac output = stroke volume × heart rate

Use all the information to describe what causes the increase in cardiac output:

• from rest to medium-intensity exercise

• from medium-intensity exercise to high-intensity exercise.

You do not need to calculate cardiac output to answer this question.

[2 marks]

Rest to medium-intensity exercise

Medium-intensity exercise to high-intensity exercise

04.3 Name the type of blood vessel that controls blood flow to muscles and explain how

these blood vessels change blood flow during exercise.

[3 marks]

Name of blood vessel

Explanation

Mark scheme

Show the mark scheme The mark scheme provides answers for all three parts. For 04.1, it shows the correct numbering for Table 2: Pulmonary vein (1), Left atrium (2), Left atrioventricular valve (3), Left ventricle (4), Left semi-lunar valve (5), Aorta (6), awarding 2 marks for all correct. For 04.2, it awards 2 marks for stating increased stroke volume and increased heart rate for rest to medium-intensity exercise, and increased heart rate for medium to high-intensity exercise. For 04.3, it awards 3 marks for naming 'Arteriole', explaining that (circular/smooth) muscle relaxes, and vasodilation widens the lumen to increase blood flow.

Question Marking Guidance Mark Comments

Aorta 6 Pulmonary vein 1 Ignore numbers 7-12

Left

Left semi-lunar Penalise more than

atrioventricular 3 5

valve one use of numbers

valve

Right 1-6

atrioventricular Vena cava

valve 2

04.1 Left atrium 2 Left ventricle 4 (2 x

Right atrium Right ventricle AO1)

Pulmonary artery Right semi-lunar

valve

All correct 2 marks,

3–4 correct 1 mark,

0–2 correct 0 marks

1. Accept description

1. (Rest to medium-intensity exercise)

of increased stroke

Increased stroke volume and increased heart

volume

rate; 2

2. Reject reference to

04.2 2. (Medium-intensity exercise to high-intensity (2 x

increase stroke

exercise) AO2)

volume here.

Increased heart rate;

1. and 2. Ignore

figures.

1. Arteriole;

2. (Circular/smooth) muscle relaxes;

3. Vasodilation increases blood flow

04.3 (1 x

OR AO1, 2

x AO2)

Widens/dilates (lumen of) blood vessel so

increases blood flow;

How to answer it

Flow of Blood and Cardiac Output Study Guide

What this question tests

This question assesses your knowledge of the human cardiovascular system, specifically tracing the anatomical pathway of blood flow through the heart chambers and valves. It tests your ability to interpret graphical data regarding cardiac cycle volumes and heart rates during different exercise intensities, and applies your understanding of vascular control (arterioles and smooth muscle relaxation) in meeting metabolic demands.

Question 0.4.1

Pathway of Blood Through the Heart

Ordering structures leading into and through the left ventricle

✅ Correct Answers (Table Mapping)

  • Pulmonary vein: 1
  • Left atrium: 2
  • Left atrioventricular valve: 3
  • Left ventricle: 4 (given)
  • Left semi-lunar valve: 5
  • Aorta: 6

💡 Key Knowledge

  • Oxygenated blood returns from the lungs via the pulmonary veins into the left atrium.
  • Blood passes through the bicuspid (left atrioventricular) valve into the left ventricle.
  • Contraction of the left ventricle forces blood through the aortic semi-lunar valve into the aorta.

🧠 Exam Technique

  • Strict marking scale: All 6 correct = 2 marks; 3 to 4 correct = 1 mark; 0 to 2 correct = 0 marks.
  • Make sure you use numbers 1 to 6 exclusively without repetition.

❌ Common Errors

  • Confusing the left and right sides of the heart (remember diagrams are shown from the perspective of the person whose heart it is: left is on your right of the page).
  • Including structures on the right side of the heart (like the vena cava or pulmonary artery) which are not part of the pathway specified leading specifically to the left ventricle.
Total for 04.1: [2 marks]
Question 0.4.2

Cardiac Output and Exercise Intensity

Interpreting bar charts to explain changes in cardiac output

✅ Correct Answers

  • Rest to medium-intensity exercise: Increased stroke volume and increased heart rate.
  • Medium-intensity exercise to high-intensity exercise: Increased heart rate (only).

💡 Key Knowledge

  • Cardiac output = Stroke volume × Heart rate
  • Stroke volume is calculated as: Volume just before contraction minus Volume at the end of contraction.
  • During high-intensity exercise, stroke volume plateaus or stops increasing, so further increases in cardiac output rely solely on raising heart rate.

🧠 Exam Technique

  • Read the prompt carefully: You do not need to calculate cardiac output numbers. Use the visual bar graph trends directly.
  • For the first transition, both factors must be mentioned to secure the mark.

❌ Common Errors

  • Stating that stroke volume increases between medium-intensity and high-intensity exercise (the bar heights for volume before/after contraction remain nearly identical).
  • Wasting time performing unnecessary mathematical calculations using the scale on Figure 2.
Total for 04.2: [2 marks]
Question 0.4.3

Control of Blood Flow to Muscles

Identifying blood vessels and explaining mechanisms of vasodilation

✅ Correct Answers

  • Name of blood vessel: Arteriole.
  • Explanation: Circular/smooth muscle relaxes, causing vasodilation which widens the lumen and increases blood flow to the muscles.

💡 Key Knowledge

  • Arterioles are small vessels situated between arteries and capillaries containing rings of smooth muscle whose contraction or relaxation controls blood distribution.
  • Relaxation of smooth muscle decreases resistance and increases volumetric flow to active tissues during exercise.

🧠 Exam Technique

  • This is a classic 3-mark breakdown: 1 mark for naming the vessel correctly, and 2 marks for the mechanism (relaxation of smooth muscle leading to vasodilation / wider lumen).
  • Ensure you specify smooth or circular muscle; generic references to "muscles" will not gain credit.

❌ Common Errors

  • Naming capillaries or arteries instead of arterioles. Capillaries do not have muscular walls to actively control flow, and large arteries act more on pressure damping.
  • Saying muscle "contracts" to widen the vessel (smooth muscle relaxation causes widening/vasodilation).
Total for 04.3: [3 marks]

Topics

Biology · 3.3 Organisms exchange substances with their environment

Question and mark scheme from the AQA AS Level Biology examination, Paper 2, June 2023. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.