You are viewing a free preview of this lesson.
Subscribe to unlock all 10 lessons in this course and every other course on LearningBro.
This lesson covers the mechanics of breathing — how air is drawn into and pushed out of the lungs — as required by the Edexcel GCSE PE specification (1PE0 — Topic 1). You need to understand the role of the diaphragm, intercostal muscles, and changes in pressure and volume during inspiration (breathing in) and expiration (breathing out), both at rest and during exercise.
Breathing (also called ventilation) is the physical process of moving air into and out of the lungs. It has two phases:
Breathing is controlled by two main sets of muscles:
| Muscle | Location | Role in Breathing |
|---|---|---|
| Diaphragm | A dome-shaped sheet of muscle below the lungs, separating the chest cavity from the abdomen | The primary breathing muscle |
| External intercostal muscles | Between the ribs (on the outside) | Raise the ribcage during inspiration |
| Internal intercostal muscles | Between the ribs (on the inside) | Pull the ribcage down during forced expiration |
During normal, quiet inspiration (breathing in at rest):
graph TD
A["Diaphragm contracts<br>(flattens)"] --> D["Chest cavity<br>volume increases"]
B["External intercostals<br>contract"] --> C["Ribcage moves<br>up and out"]
C --> D
D --> E["Pressure inside<br>lungs decreases"]
E --> F["Air rushes IN<br>(inspiration)"]
style A fill:#4a90d9,color:#fff
style F fill:#27ae60,color:#fff
During normal, quiet expiration (breathing out at rest):
Important: At rest, expiration is largely a passive process — it relies on the relaxation of muscles and the natural elasticity of the lungs (they spring back like an elastic band). The internal intercostal muscles are not used during quiet breathing.
During exercise, the body needs to take in more oxygen and expel more carbon dioxide. Both inspiration and expiration become more active and forceful:
Subscribe to continue reading
Get full access to this lesson and all 10 lessons in this course.