Question 1

What is the difference between cardiac output and stroke volume?

Accepted Answer

Cardiac output is the total volume of blood pumped by the heart per minute, measured in litres per minute. Stroke volume is the volume of blood pumped per heartbeat, measured in millilitres. The relationship is: cardiac output = stroke volume × heart rate. During exercise, both stroke volume and heart rate increase to raise cardiac output, delivering more oxygen to working muscles.

Question 2

How does the respiratory system adapt to long-term exercise?

Accepted Answer

Long-term exercise leads to several adaptations in the respiratory system. The intercostal muscles and diaphragm become stronger, allowing for deeper and more efficient breaths. Vital capacity (the maximum amount of air that can be exhaled after a deep breath) increases, and the number of capillaries around the alveoli grows, improving gas exchange. These changes enhance oxygen uptake and carbon dioxide removal, delaying fatigue.

Question 3

Why does my heart rate increase during exercise?

Accepted Answer

During exercise, your muscles require more oxygen to produce energy. The brain detects this increased demand and sends signals via the sympathetic nervous system to the heart, causing it to beat faster. Hormones like adrenaline also stimulate the heart. The increased heart rate raises cardiac output, delivering more oxygenated blood to the muscles and removing waste products like carbon dioxide more quickly.

Question 4

What is the role of the alveoli in gas exchange?

Accepted Answer

Alveoli are tiny air sacs in the lungs where gas exchange occurs. They have a large surface area and thin walls (one cell thick) to allow efficient diffusion. Oxygen from inhaled air diffuses across the alveolar wall into the surrounding capillaries, where it binds to haemoglobin in red blood cells. At the same time, carbon dioxide diffuses from the blood into the alveoli to be exhaled. This process is essential for supplying oxygen to the body and removing waste.

Question 5

How do I calculate cardiac output in an exam?

Accepted Answer

To calculate cardiac output, use the formula: Cardiac Output (CO) = Stroke Volume (SV) × Heart Rate (HR). For example, if stroke volume is 70 ml and heart rate is 72 bpm, then CO = 70 × 72 = 5040 ml/min, which is 5.04 L/min. Always include units in your answer. If given values in different units (e.g., stroke volume in litres), convert them first to ensure consistency.

Question 6

What is the difference between aerobic and anaerobic respiration in terms of the cardiovascular and respiratory systems?

Accepted Answer

Aerobic respiration requires oxygen, so during aerobic exercise, the cardiovascular and respiratory systems work to deliver sufficient oxygen to muscles. Heart rate and breathing rate increase steadily to meet demand. Anaerobic respiration occurs without oxygen, typically during high-intensity exercise. The cardiovascular and respiratory systems cannot supply oxygen fast enough, so the body relies on stored energy. This leads to a rapid increase in heart rate and breathing rate, but oxygen debt builds up, causing fatigue and requiring deep breathing after exercise to repay it.

The cardiovascular and respiratory systems

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Related Topics in OCR GCSE Physical Education

Aerobic and anaerobic exercise

Applied anatomy and physiology

Applying the principles of training

Characteristics of skilful movement

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