How do the heart and lungs work together to deliver oxygen to the muscles?
The structure and function of the cardio-respiratory system: the heart and the double circulatory system, blood vessels and vascular shunting, heart rate, stroke volume and cardiac output, the pathway of air and gaseous exchange in the lungs.
A focused answer to Eduqas GCSE PE Component 1 on the cardio-respiratory system: the heart and double circulation, blood vessels and vascular shunting, cardiac output (with a calculation), the pathway of air, and gaseous exchange at the alveoli.
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What this dot point is asking
Eduqas wants you to describe the structure and function of the heart, blood vessels and lungs, trace blood and air through the body, define and calculate cardiac output, explain vascular shunting, and describe gaseous exchange.
The heart and the double circulatory system
Blood passes through the heart twice on one circuit (the double circulatory system): the pulmonary circuit runs heart to lungs and back, and the systemic circuit runs heart to body and back. Deoxygenated blood enters the right atrium, drops into the right ventricle, and is pumped to the lungs; oxygenated blood returns to the left atrium, drops into the left ventricle, and is pumped to the body through the aorta.
Heart rate, stroke volume and cardiac output
The blood vessels and vascular shunting
During exercise, vascular shunting redistributes blood: the arteries to the working muscles vasodilate (widen) to increase flow, while the vessels to organs that need less blood (the gut) vasoconstrict (narrow). The result is that a much larger share of the cardiac output reaches the muscles.
The pathway of air and gaseous exchange
Air travels through the mouth and nose, down the trachea, into the bronchi, the bronchioles, and finally the alveoli (tiny air sacs). At the alveoli, gaseous exchange happens by diffusion: oxygen diffuses from the alveoli (high concentration) into the blood in the surrounding capillaries, and carbon dioxide diffuses from the blood into the alveoli to be breathed out. The alveoli are adapted for this: a huge surface area, walls one cell thick (a short diffusion distance), a rich capillary network and moist walls all speed up diffusion. Breathing itself is driven by the diaphragm and intercostal muscles, which change the volume and pressure of the chest to draw air in and push it out.
Exam-style practice questions
Practice questions written in the style of WJEC Eduqas exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Eduqas 20193 marksA performer has a heart rate of 72 beats per minute and a stroke volume of 75 millilitres at rest. Calculate their cardiac output and state the units.Show worked answer →
A Component 1 calculation. Award marks for the formula, the value and the units.
Cardiac output is heart rate multiplied by stroke volume: millilitres per minute, which is litres per minute.
Markers want the formula shown, the value, and the correct units (millilitres or litres per minute). Adding instead of multiplying, or omitting the units, loses marks.
Eduqas 20214 marksExplain how vascular shunting redistributes blood during exercise and why this benefits a performer.Show worked answer →
A 4-mark application question on blood redistribution.
Award marks for: during exercise the working muscles need more oxygen. Vascular shunting redistributes blood by vasodilation (widening) of the arteries supplying the working muscles, increasing blood flow to them, and vasoconstriction (narrowing) of the vessels supplying organs that need less blood at that moment, such as the gut. The benefit: more oxygenated blood reaches the muscles, delivering oxygen for aerobic respiration and removing carbon dioxide and lactic acid faster, so the performer can keep working at a high intensity.
Markers reward vasodilation and vasoconstriction used correctly and a clear statement that more blood and oxygen reach the working muscles.
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Sources & how we know this
- Eduqas GCSE (9-1) Physical Education C550QS specification — Eduqas (2016)