Describe the oxygen pressure gradient at the alveoli at rest.

Alveolar air has a pO₂ of about 100 mmHg. Blood arriving in the capillaries has a pO₂ of about 40 mmHg, so oxygen diffuses into the blood.

Describe the carbon dioxide pressure gradient at the alveoli at rest.

Blood arriving at the alveoli has a pCO₂ of about 45 mmHg against about 40 mmHg in the alveoli. Carbon dioxide diffuses into the alveoli to be breathed out.

Which features of the alveoli make gas exchange efficient?

Alveoli have a huge surface area and walls only one cell thick. A dense capillary network and a moist lining also speed diffusion.

Describe gas exchange at the muscles at rest.

Arterial blood reaching the muscles has a higher pO₂ than the muscle cells. Oxygen diffuses into the muscle, and carbon dioxide diffuses out into the blood.

OCR A-Level Physical Education H555

Skeletal and Muscular Systems

Topic overview Shoulder, elbow and wrist joints and muscles Hip, knee and ankle joints and muscles Planes of movement, muscle roles and contractions Analysing movement in sporting actions Motor units and muscle fibre types

The Cardiovascular System

Topic overview Heart rate, stroke volume and cardiac output at rest The cardiac cycle and conduction system Cardiac responses to exercise and recovery The vascular shunt mechanism Venous return and heart rate regulation

The Respiratory System

Topic overview Breathing frequency, tidal volume and minute ventilation Mechanics of breathing at rest and in exercise Regulation of breathing Gas exchange at the alveoli and the muscles

Energy for Exercise

Topic overview ATP and coupled reactions The ATP-PC system The glycolytic system The aerobic system The energy continuum and intermittent exercise EPOC and the recovery process

Environmental Effects on Body Systems

Topic overview Altitude and oxygen delivery Acclimatisation and timing arrival at altitude Exercise in the heat and cardiovascular drift

Diet, Nutrition and Ergogenic Aids

Topic overview Components of a balanced diet Energy balance, meals and hydration Anabolic steroids, EPO and HGH Blood doping, intermittent hypoxic training and cooling aids Carbohydrate loading and supplements

Aerobic Training

Topic overview VO₂max and the factors that affect it Testing aerobic capacity Continuous training, HIIT and target heart rates Adaptations to aerobic training

Strength and Flexibility Training

Topic overview Types of strength and strength testing Strength training methods Adaptations to strength training Types of flexibility and flexibility testing Flexibility training methods and adaptations

Periodisation of Training

Topic overview Macrocycles, mesocycles and microcycles Training phases and tapering Planning a personal health and fitness programme

Training and Lifestyle Diseases

Topic overview Atherosclerosis and coronary heart disease Heart attack and stroke Asthma and COPD

Injury Prevention and Rehabilitation

Topic overview Acute and chronic injuries Risk factors, warm-up and cool-down SALTAPS, PRICE and concussion Fractures, joint injuries and muscle damage Treatments for sporting injuries

Biomechanical Principles and Levers

Topic overview Newton's laws and force calculations Forces and free body diagrams Centre of mass and stability Levers and mechanical advantage Limb kinematics, force plates and wind tunnels

Linear and Angular Motion

Topic overview Linear motion, distance and displacement Speed, velocity and acceleration Graphs of linear motion Angular motion and the axes of rotation Moment of inertia and conservation of angular momentum

Fluid Mechanics and Projectile Motion

Topic overview Air resistance and drag Factors affecting projectile distance Forces on a projectile and flight paths Bernoulli's principle and lift Spin and the Magnus effect

Skill Classification, Practice and Transfer

Topic overview Classifying skills by difficulty, environment and pacing Classifying skills by muscular involvement, continuity and organisation Whole, part, whole-part-whole and progressive part practice Massed, distributed, fixed and varied practice Transfer of learning between skills

Theories and Stages of Learning

Topic overview Operant conditioning Cognitive theory and insight learning Bandura's observational learning Fitts and Posner's stages of learning

Guidance and Feedback

Topic overview Verbal and visual guidance Manual and mechanical guidance Intrinsic, extrinsic, positive and negative feedback Knowledge of performance and knowledge of results

Memory Models

Topic overview Atkinson and Shiffrin's multi-store model Selective attention Craik and Lockhart's levels of processing

Personality and Attitudes

Topic overview Trait theory of personality Social learning and interactionist perspectives Attitudes and the triadic model Persuasive communication and cognitive dissonance

Motivation and Arousal

Topic overview Intrinsic and extrinsic motivation Rewards and motivation in coaching Arousal and drive theory Inverted-U and catastrophe theories

Anxiety

Topic overview State and trait anxiety Somatic and cognitive anxiety The zone of optimal functioning

Aggression

Topic overview Aggression and assertion Instinct and social learning theories of aggression Frustration-aggression and aggressive cue hypotheses

Social Facilitation and Group Dynamics

Topic overview Social facilitation and inhibition Evaluation apprehension and reducing social inhibition Groups and Tuckman's stages of development Steiner's model, the Ringelmann effect and social loafing

Goal Setting

Topic overview Outcome, performance and process goals How goal setting improves performance The SMART principle

Attribution

Topic overview Weiner's model: locus of causality and stability Controllability, self-serving bias and attribution retraining Learned helplessness and mastery orientation

Confidence and Self-Efficacy

Topic overview Sports confidence, self-efficacy and self-esteem Vealey's model of sports confidence Bandura's four sources of self-efficacy Building confidence in performers

Leadership

Topic overview Effective, emergent and prescribed leaders Autocratic, democratic and laissez-faire styles Trait, social learning and interactionist theories of leadership Chelladurai's multi-dimensional model

Stress Management

Topic overview Stress and stressors in sport Self-talk, thought stopping and rational thinking Mental rehearsal, imagery, goal setting and mindfulness Relaxation, biofeedback, centring and breathing control

Sport in Pre-Industrial and Industrial Britain

Topic overview Popular recreation in pre-industrial Britain Urbanisation, rational recreation and the railways Amateurism and professionalism in Victorian sport Public schools and the cult of athleticism

Sport in the 20th and 21st Centuries

Topic overview Amateurism and professionalism in the 20th century Social change and sport in 20th-century Britain Class, gender and access in 21st-century sport The globalisation of sport

The Olympic Games and Global Sporting Events

Topic overview Coubertin and the aims of the modern Olympics Berlin 1936 and Mexico City 1968 Munich 1972 and the Cold War boycotts Hosting a global sporting event

Drugs in Sport

Topic overview Legal supplements and illegal doping Why elite performers dope Consequences of doping for society, sport and performers Strategies against doping

Violence and Gambling in Sport

Topic overview Causes of player and spectator violence Implications of violence in sport Preventing violence among players and spectators Match fixing, bribery and illegal betting

Commercialisation and the Media

Topic overview What drives the commercialisation of sport Impacts of commercialisation Television, radio, press and internet coverage Positive and negative effects of the media Sport as a commodity and the golden triangle

Routes to Sporting Excellence

Topic overview From talent identification to elite performance Schools, clubs and universities in elite success UK Sport and the national institutes Drop-out from elite programmes

Modern Technology in Sport

Topic overview Technology and elite performance Technology and general participation Technology and fair outcomes Technology and entertainment

The Respiratory System

Gas exchange at the alveoli and the muscles

3 things to know
Component 01

Overview

Partial pressure and pressure gradients at the alveoli and the muscles, alveolar structure, myoglobin, the arterio-venous oxygen difference, the oxyhaemoglobin dissociation curve and the Bohr shift in exercise and recovery.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

What are partial pressure and a pressure gradient, and how do they drive gas exchange?

Key term

What is partial pressure?

Key term

What is a pressure gradient in gas exchange?

Questions from this subtopic

Each one with the model answer underneath.

1
What is partial pressure?
Model answer
Partial pressure is the pressure exerted by one gas within a mixture of gases. Oxygen and carbon dioxide each exert their own partial pressure.
2
What is a pressure gradient in gas exchange?
Model answer
A pressure gradient is the difference in partial pressure between two areas. Gases diffuse from high to low partial pressure, and a steeper gradient means faster diffusion.
3
Describe the oxygen pressure gradient at the alveoli at rest.
Model answer
Alveolar air has a pO₂ of about 100 mmHg. Blood arriving in the capillaries has a pO₂ of about 40 mmHg, so oxygen diffuses into the blood.
4
Describe the carbon dioxide pressure gradient at the alveoli at rest.
Model answer
Blood arriving at the alveoli has a pCO₂ of about 45 mmHg against about 40 mmHg in the alveoli. Carbon dioxide diffuses into the alveoli to be breathed out.
5
Which features of the alveoli make gas exchange efficient?
Model answer
Alveoli have a huge surface area and walls only one cell thick. A dense capillary network and a moist lining also speed diffusion.
6
Describe gas exchange at the muscles at rest.
Model answer
Arterial blood reaching the muscles has a higher pO₂ than the muscle cells. Oxygen diffuses into the muscle, and carbon dioxide diffuses out into the blood.

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Skeletal and Muscular Systems

The Cardiovascular System

The Respiratory System

Energy for Exercise

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