Respiratory system — AQA A-Level Physical Education
Test yourself on Respiratory system with AQA A-Level practice questions.
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Your focus
- Understanding of lung volumes and the impact of and on physical activity and sport.
Respiratory system exam tips
Quick Revision Summary (Key Takeaway)
The respiratory system is the network of organs and tissues that facilitate gas exchange, bringing oxygen into the body and removing carbon dioxide. In AQA A-Level Physical Education, you must understand its structure, mechanics of breathing, neural and chemical control, and how it adapts to exercise and training.
Topic Overview
The respiratory system is responsible for the intake of oxygen and removal of carbon dioxide, essential for energy production during exercise. At A-Level, you must understand the anatomy of the respiratory tract, the mechanics of breathing (inspiration and expiration at rest and during exercise), and the control of breathing by the nervous system.
This topic underpins performance in physical activity, as efficient gas exchange directly affects aerobic capacity and endurance. It also links to other areas such as the cardiovascular system, energy systems, and training adaptations, making it a core component of the AQA A-Level Physical Education specification.
Key Concepts
- →Structure of the respiratory system: nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles, alveoli, and the role of the diaphragm and intercostal muscles.
- →Mechanics of breathing: inspiration and expiration at rest and during exercise, including the roles of the diaphragm, external and internal intercostal muscles, and accessory muscles.
- →Gas exchange: diffusion of oxygen and carbon dioxide across the alveolar-capillary membrane driven by partial pressure gradients.
- →Neural and chemical control: medulla oblongata, chemoreceptors (central and peripheral), and the role of blood pH, pCO2, and pO2.
- →Respiratory adaptations to training: increased tidal volume, vital capacity, pulmonary ventilation, and efficiency of gas exchange.
Examiner Tips
- 💡Always use specific terminology such as 'partial pressure', 'diffusion gradient', 'medulla oblongata', and 'chemoreceptors' to access higher marks.
- 💡When explaining responses to exercise, structure your answer using the stimulus-receptor-coordinator-effector-response model to ensure logical flow.
- 💡For calculation questions, show all working and include units; marks are often awarded for correct units and intermediate steps.
Common Mistakes
- Students often think that breathing is controlled by the lungs themselves. Correction: Breathing is controlled by the medulla oblongata in the brainstem, which responds to chemical stimuli from chemoreceptors.
- Many believe that oxygen is carried primarily in the blood plasma. Correction: About 98% of oxygen is carried bound to haemoglobin in red blood cells; only 2% dissolves in plasma.
- Students sometimes confuse partial pressure with concentration. Correction: Partial pressure is the pressure exerted by a single gas in a mixture, and it drives diffusion; concentration is the amount of gas per unit volume.
Revision Plan
- 1Week 1: Learn the anatomy of the respiratory system using diagrams and labelling exercises. Focus on the pathway of air and the structure of alveoli.
- 2Week 1: Study the mechanics of breathing at rest and during exercise. Create a table comparing inspiration and expiration, including muscle actions and pressure changes.
- 3Week 2: Understand gas exchange and partial pressures. Practice explaining the diffusion of oxygen and carbon dioxide using correct terminology.
- 4Week 2: Learn the neural and chemical control of breathing. Create a flowchart of the control pathway and test yourself on the roles of chemoreceptors.
- 5Week 2: Review adaptations to training and complete past paper questions on the respiratory system, marking your answers against the mark scheme.
Exam Question Types
- 📋Short-answer questions (2-4 marks) asking for definitions or explanations of specific structures or processes, e.g., 'Define tidal volume' or 'Explain the role of the diaphragm during inspiration'.
- 📋Data analysis questions (4-6 marks) where you interpret spirometry traces or graphs of ventilation during exercise and explain the physiological reasons for the changes.
- 📋Extended writing questions (6-9 marks) requiring a detailed explanation of how the respiratory system responds to exercise or training, often linking to other systems.
- 📋Calculation questions (2-3 marks) involving VO2 max, pulmonary ventilation, or oxygen uptake, requiring correct formula application and units.
Command Word Expectations (AQA)
Describe
Provide a detailed account of the features or process, including specific names and functions. No explanation of why is required, but accuracy is essential.
Explain
Give reasons or mechanisms for a process. You must use causal language (because, therefore, as a result) and link structure to function.
Evaluate
Make a judgement based on evidence, considering strengths and weaknesses. You must weigh up factors and come to a justified conclusion.
How Students Lose Marks (Examiner Pitfalls)
Pitfall: Students often confuse the partial pressures of oxygen and carbon dioxide in the blood and alveoli, leading to incorrect explanations of gas exchange direction.
❌ Weak Answer (Loses Marks):Oxygen moves from the blood to the alveoli because there is more oxygen in the blood.
Example improved answer:Oxygen moves from the alveoli to the blood by diffusion because the partial pressure of oxygen (pO2) is higher in the alveoli (approximately 104 mmHg) than in the deoxygenated blood of the pulmonary capillaries (approximately 40 mmHg). Carbon dioxide moves in the opposite direction because its partial pressure (pCO2) is higher in the blood (approximately 45 mmHg) than in the alveoli (approximately 40 mmHg).
Examiner Tip: Always refer to partial pressure gradients, not just 'concentration', and state the direction of movement for each gas. Use the terms 'diffusion' and 'partial pressure' explicitly.
Pitfall: When explaining neural control of breathing, students frequently omit the role of chemoreceptors and the medulla oblongata, focusing only on the lungs.
❌ Weak Answer (Loses Marks):Breathing is controlled by the lungs and you breathe faster when you exercise because your muscles need more oxygen.
Example improved answer:Breathing is controlled by the respiratory centres in the medulla oblongata. Chemoreceptors detect changes in blood pH, pCO2, and pO2. During exercise, increased pCO2 and decreased pH stimulate the chemoreceptors, which send impulses to the medulla. The medulla then increases the rate and depth of breathing via the phrenic and intercostal nerves, which stimulate the diaphragm and external intercostal muscles.
Examiner Tip: Name the specific receptors (central and peripheral chemoreceptors), the integrating centre (medulla oblongata), and the effector muscles. Use the correct sequence: stimulus, receptor, coordinator, effector, response.
Step-by-Step Worked Solutions
Question: Calculate the oxygen uptake (VO2) in ml/kg/min for a 70 kg athlete who consumes 3.5 litres of oxygen per minute during maximal exercise. Show your working.
- 1.Step 1: Identify given facts: oxygen consumption = 3.5 L/min, body mass = 70 kg.
- 2.Step 2: Convert litres to millilitres: 3.5 L = 3500 ml.
- 3.Step 3: Apply formula: VO2 (ml/kg/min) = (oxygen consumption in ml/min) / body mass in kg.
- 4.Step 4: Calculate: 3500 ml/min / 70 kg = 50 ml/kg/min.
Final Answer: The athlete's oxygen uptake is 50 ml/kg/min.
Question: Explain how the respiratory system responds to a single bout of moderate-intensity exercise. (6 marks)
- 1.Step 1: Identify the key responses: increased breathing rate and depth (tidal volume).
- 2.Step 2: Explain the neural control: chemoreceptors detect increased pCO2 and decreased pH, stimulating the medulla oblongata.
- 3.Step 3: Describe the mechanical changes: increased stimulation of diaphragm and external intercostal muscles via phrenic and intercostal nerves.
- 4.Step 4: Link to gas exchange: increased ventilation maintains partial pressure gradients for oxygen and carbon dioxide.
- 5.Step 5: Mention additional responses: increased pulmonary blood flow and recruitment of more alveoli.
Final Answer: During moderate exercise, breathing rate and tidal volume increase due to chemoreceptor detection of rising pCO2 and falling pH. The medulla oblongata stimulates the diaphragm and external intercostals more forcefully, increasing ventilation. This maintains partial pressure gradients for efficient gas exchange, supported by increased pulmonary blood flow and alveolar recruitment.
Active Recall Memory Test
What is the partial pressure of oxygen in the alveoli and in deoxygenated blood?
Key Fact: Alveoli: approximately 104 mmHg; deoxygenated blood: approximately 40 mmHg.
Which muscles are responsible for inspiration during exercise?
Key Fact: Diaphragm, external intercostal muscles, and accessory muscles such as sternocleidomastoid and scalenes.
What is the role of the medulla oblongata in breathing?
Key Fact: It contains the respiratory centres that generate rhythmic nerve impulses to the respiratory muscles, adjusting rate and depth based on chemoreceptor input.
Define tidal volume.
Key Fact: The volume of air inhaled or exhaled during a normal breath, approximately 500 ml at rest.
Frequently Asked Questions
What is the difference between breathing and respiration?
Breathing (ventilation) is the mechanical process of moving air into and out of the lungs, involving muscles and pressure changes. Respiration is the biochemical process within cells that uses oxygen to produce ATP, releasing carbon dioxide as a waste product. In A-Level PE, you must distinguish between external respiration (gas exchange in the lungs) and internal respiration (gas exchange at tissues).
How does the respiratory system control breathing during exercise?
During exercise, chemoreceptors detect increased carbon dioxide and decreased blood pH. These send signals to the medulla oblongata, which increases nerve impulses to the diaphragm and intercostal muscles. This raises breathing rate and depth, increasing oxygen intake and carbon dioxide removal. Proprioceptors in muscles and joints also stimulate the medulla at the start of exercise.
What are the long-term effects of training on the respiratory system?
Long-term training increases tidal volume, vital capacity, and pulmonary ventilation during maximal exercise. It also strengthens respiratory muscles, improves alveolar-capillary diffusion, and increases the number of alveoli and capillaries. These adaptations enhance oxygen delivery and carbon dioxide removal, improving endurance performance.
Why does breathing rate increase during exercise?
Breathing rate increases to meet the higher oxygen demand of working muscles and to remove excess carbon dioxide. Chemoreceptors detect rising pCO2 and falling pH, triggering the medulla oblongata to stimulate faster and deeper breathing. This maintains partial pressure gradients for efficient gas exchange.
What is VO2 max and how is it calculated?
VO2 max is the maximum rate of oxygen consumption during intense exercise, reflecting aerobic fitness. It is calculated as the maximum volume of oxygen used per minute per kilogram of body mass (ml/kg/min). It can be measured directly during a graded exercise test or estimated using submaximal tests like the Cooper run.
How do you answer a 6-mark question on the respiratory system?
For a 6-mark question, you need six distinct points, each with explanation. Structure your answer using a logical sequence: stimulus, receptor, coordinator, effector, response, and link to performance. Use correct terminology and ensure each point is developed. For example, when explaining exercise responses, cover neural control, mechanical changes, and gas exchange.