Breathing Mechanics and Cardiac Output
How the body takes in air and moves blood during exercise: the muscles of breathing, the lung volumes on a spirometer, and how to work out cardiac output from stroke volume and heart rate.
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Breathing and pumping 🫁
To keep moving, the body must take in oxygen and pump blood to the muscles. Breathing is driven by muscles that change the size of the chest, and the heart pushes out a measured amount of blood each minute. This module looks at the mechanics of breathing and how to work out cardiac output.
Key words 🔑
Learn these four terms before you study breathing and cardiac output.
Breathing in or out? 🆚
Different muscles work to move air into and out of the lungs at rest.
Grade 9 thinking 💡
Cardiac output equals stroke volume multiplied by heart rate, and this is a gift-mark calculation, so learn it well. During exercise stroke volume, heart rate and breathing all rise so more oxygen reaches the muscles. In hard exercise extra muscles such as the sternocleidomastoid help you breathe in more deeply.
Match the breathing term 🔗
- diaphragm
- intercostal muscles
- tidal volume
- residual volume
- a dome-shaped muscle below the lungs
- muscles between the ribs that move the rib cage
- the air breathed in or out in one normal breath
- the air left in the lungs after breathing out fully
Match the heart term 🧩
- stroke volume
- heart rate
- cardiac output
- anticipatory rise
- the blood pumped out of the heart in one beat
- the number of beats each minute
- the blood pumped out of the heart each minute
- the rise in heart rate just before exercise starts
What is cardiac output? ❓
What is cardiac output?
- The amount of blood pumped out of the heart each minute.
- The blood pumped out of the heart in one beat.
- The number of times the heart beats each minute.
Muscles for breathing in ✅
Select the TWO muscles used to breathe in at rest.
- The diaphragm.
- The intercostal muscles.
- The abdominal muscles.
- The sternocleidomastoid.
Order breathing in 🪜
An interactive activity.
Summarise the ideas 📝
The _____ is a dome-shaped muscle that flattens when you breathe in. The air breathed in or out in one normal breath is called _____ volume. The blood pumped out of the heart in one beat is the _____ volume. Cardiac output is stroke volume multiplied by _____ rate. During exercise all of these values _____.
Work out cardiac output 🔢
An interactive activity.
Find what rises in exercise 🖍️
An interactive activity.
Which measure is it? 🧭
An interactive activity.
Explain exercise changes ✍️
An interactive activity.