How does the heart and blood deliver oxygen to working muscles during exercise?
The structure and function of the cardiovascular system, the pathway of blood through the heart, heart rate, stroke volume and cardiac output, the role of blood vessels and vascular shunting, and the cardiovascular response to exercise.
A focused answer to OCR GCSE PE Component 01 on the cardiovascular system: the structure of the heart and the double circulatory system, the blood vessels, heart rate, stroke volume and cardiac output (with a calculation), vascular shunting, and the response to exercise.
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What this dot point is asking
OCR wants you to describe the structure and function of the heart and blood vessels, trace blood through the double circulatory system, define and calculate cardiac output, explain vascular shunting, and describe the cardiovascular response to exercise.
Structure and function of the heart
This is the double circulatory system: blood passes through the heart twice on one full circuit. The pulmonary circuit carries blood from the heart to the lungs and back; the systemic circuit carries blood from the heart to the rest of the body and back.
The pathway of blood through the heart
Deoxygenated blood from the body enters the right atrium, passes into the right ventricle, and is pumped through the pulmonary artery to the lungs, where it picks up oxygen. Oxygenated blood returns from the lungs to the left atrium, passes into the left ventricle, and is pumped out through the aorta to the whole body.
Heart rate, stroke volume and cardiac output
The blood vessels
A simple memory aid: Arteries carry blood Away from the heart. Most arteries carry oxygenated blood (the exception is the pulmonary artery to the lungs); most veins carry deoxygenated blood (the exception is the pulmonary vein from the lungs).
Vascular shunting
During exercise the working muscles need far more oxygen, so blood flow is redistributed by vascular shunting. The arteries supplying the working muscles vasodilate (widen) to increase blood flow there, while the vessels supplying organs that do not need as much blood (such as the gut) vasoconstrict (narrow) to reduce flow. The result is that a much larger share of the cardiac output reaches the muscles, delivering oxygen and removing carbon dioxide and lactic acid.
The cardiovascular response to exercise
As exercise begins, heart rate rises (so more blood is pumped per minute), stroke volume rises (the heart pumps harder), and vascular shunting directs blood to the muscles. Over time, regular endurance training produces long-term adaptations such as cardiac hypertrophy (a larger, stronger heart), a higher stroke volume and a lower resting heart rate (bradycardia), all covered in the effects of exercise topic.
Exam-style practice questions
Practice questions written in the style of OCR exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
OCR 20193 marksA performer has a heart rate of 70 beats per minute and a stroke volume of 80 millilitres at rest. Calculate their cardiac output and state the units.Show worked answer →
A Component 01 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 per minute or litres per minute). Forgetting the units, or adding instead of multiplying, loses marks.
OCR 20224 marksExplain how vascular shunting redistributes blood flow during exercise and why this benefits a performer.Show worked answer →
A 4-mark application question on the redirection of blood.
Award marks for: during exercise the body needs more oxygen at the working muscles. Vascular shunting redistributes blood by vasodilation (widening) of the arteries and arterioles supplying the working muscles, increasing blood flow to them, and vasoconstriction (narrowing) of the vessels supplying organs that do not need as much blood at that moment, such as the gut.
The benefit: more oxygenated blood reaches the muscles, delivering more oxygen for aerobic respiration and removing carbon dioxide and lactic acid faster, so the performer can keep working at a high intensity.
Markers reward the terms vasodilation and vasoconstriction used correctly and a clear statement that more blood (and oxygen) reaches the working muscles.
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Sources & how we know this
- OCR GCSE (9-1) Physical Education J587 specification — OCR (2016)