The structure and function of the heart, the pathway of blood, the components of cardiac output, blood vessels and vascular shunting during exercise.

A focused answer to AQA GCSE PE on the cardiovascular system: the structure of the heart, the double circulatory system, cardiac output, the blood vessels and vascular shunting during exercise.

Generated by Claude Opus 4.88 min answerUpdated 2026-06-02

Reviewed by: AI editorial process; not yet individually human-reviewed

Have a quick question? Jump to the Q&A page

Jump to a section

What this dot point is asking
Structure and pathway of the heart
Cardiac output
Blood vessels and vascular shunting
How the three measures fit together

What this dot point is asking

AQA wants you to describe the structure of the heart, the pathway of blood through a double circulatory system, how cardiac output is made from heart rate and stroke volume, the three blood vessel types, and how vascular shunting redirects blood during exercise.

Structure and pathway of the heart

The heart has four chambers: two atria (top) and two ventricles (bottom). The right side handles deoxygenated blood and the left side handles oxygenated blood. The valves stop blood flowing backwards.

Cardiac output

For example, a heart rate of $70$ beats per minute and a stroke volume of $70$ ml gives a cardiac output of $70 \times 70 = 4900$ ml per minute. During exercise both heart rate and stroke volume rise, so cardiac output increases to deliver more oxygen to the muscles. A trained endurance athlete has a larger, stronger heart, so each beat ejects more blood (a higher stroke volume). That lets them reach a high cardiac output at a lower heart rate, and it explains their low resting heart rate, because at rest the same blood need is met with fewer, more powerful beats.

Calculating cardiac output and reading the change with exercise

Write the equation

Start every cardiac output question with $Q = HR \times SV$ so the marker can see your method.

Substitute the resting values

For a performer at rest with $HR = 65$ beats per minute and $SV = 75$ ml, the resting cardiac output is $Q = 65 \times 75 = 4875$ ml per minute.

Substitute the exercise values

During hard exercise the same performer reaches $HR = 180$ beats per minute and $SV = 110$ ml, so $Q = 180 \times 110 = 19800$ ml per minute (about $19.8$ litres per minute).

Interpret the result

Cardiac output has risen roughly fourfold. State the consequence: far more oxygenated blood reaches the working muscles each minute, supporting aerobic energy release and clearing carbon dioxide. Always keep the unit (ml per minute) attached.

Blood vessels and vascular shunting

Arteries: carry blood away from the heart at high pressure, with thick muscular walls.
Capillaries: tiny, thin-walled vessels where gas exchange (oxygen and carbon dioxide) takes place.
Veins: carry blood back to the heart at low pressure, with valves to prevent backflow.

How the three measures fit together

Heart rate, stroke volume and cardiac output are linked, and AQA likes to test the relationship. If a question gives any two of the three, you can find the third by rearranging $Q = HR \times SV$ . For instance, given a cardiac output of $20000$ ml per minute and a heart rate of $200$ beats per minute, stroke volume is $SV = Q \div HR = 20000 \div 200 = 100$ ml. Maximum heart rate is estimated as $220$ minus your age, so a 16 year old has an estimated maximum of about $204$ beats per minute; training does not raise this maximum, but it raises the stroke volume the heart can deliver at any heart rate.

Common traps

Saying veins carry deoxygenated blood and arteries oxygenated blood as a rule: This is usually true, but the pulmonary artery carries deoxygenated blood and the pulmonary vein carries oxygenated blood. Define vessels by direction of flow (arteries away from the heart, veins towards it), not oxygen content.
Forgetting the units in cardiac output: State stroke volume in ml and heart rate in beats per minute, then give cardiac output per minute. A bare number loses the unit mark.
Confusing vasodilation and vasoconstriction: Vasodilation widens vessels to increase flow to working muscles; vasoconstriction narrows them to reduce flow to inactive areas. Both happen at once during shunting.
Thinking training raises maximum heart rate: It does not. Training lowers resting heart rate and raises stroke volume, so the heart works more efficiently at the same effort.

Exam-style practice questions

Practice questions written in the style of AQA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.

AQA 20183 marksA performer has a heart rate of 60 beats per minute and a stroke volume of 80 ml at rest. Calculate their cardiac output and state the unit.

Show worked answer →

A Paper 1 calculation. Markers award one mark for selecting the correct equation, one for the value, and one for the unit.

Use $Q = HR \times SV$ , so $Q = 60 \times 80 = 4800$ . The unit is millilitres per minute, so the answer is $4800$ ml per minute (or $4.8$ litres per minute).

A common dropped mark is leaving off the unit, or multiplying then forgetting that the result is per minute because heart rate is per minute.

AQA 20224 marksExplain how vascular shunting and changes to cardiac output meet the demands of the working muscles during a 1500 m race.

Show worked answer →

An AO2 application question that rewards linking mechanisms to the named activity.

Award marks for: heart rate and stroke volume both rise, so cardiac output increases (from $Q = HR \times SV$ ) and more oxygenated blood is delivered per minute. Vascular shunting then redistributes that blood, the arterioles to the leg muscles vasodilate to raise flow while those to the gut and skin vasoconstrict.

Top answers tie this to the race: the legs receive more oxygen for aerobic energy release, delaying fatigue across the four laps.

Related dot points

Sources & how we know this

AQA GCSE Physical Education (8582) specification — AQA (2016)