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.
Breathing and cardiac terms
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.
The gift-mark equation
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.
- The maximum amount of oxygen the body can use in a 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
Put the steps of breathing in at rest in order, earliest first.
- The diaphragm contracts and flattens
- The chest cavity gets bigger
- The air pressure in the lungs drops
- Air rushes into the lungs
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
A performer has a stroke volume of 70 millilitres and a heart rate of 60 beats per minute. Cardiac output is stroke volume multiplied by heart rate. What is the cardiac output in millilitres per minute?
Find what rises in exercise
Tap the TWO values that increase during exercise.
- Heart rate
- Residual volume
- Tidal volume
- The number of lungs
- The number of heart chambers
Which measure is it?
Decide which measure each description is.
- The blood pumped out of the heart in a single beat
- The number of times the heart beats each minute
- The total blood pumped out of the heart each minute
Explain exercise changes
Explain how breathing and cardiac output change when a performer exercises, and why these changes happen.
- Describe how breathing changes during exercise
- Describe how cardiac output changes during exercise
- Explain why the body needs these changes