Respiratory system


Respiratory system - response to exercise

Increased breathing rate - increased rate + depth breathing caused by O2 demand and CO2 increase. anticipatory rise = minor rise. steady state exercise = breathing rate plateaus. maximum intensity - breathing rate increases until it exhaustion.

Increased tidal volume - O2 depletion = increased tidal volume allowing more air to pass to lungs. strenuous exercise = O2 diffusion rate 3x higher. minute ventilation = BRxTV (upto 15 times higher during exercise) 

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Respiratory system - long term

Increased vital capacity - provides increased / more efficient O2 supply

Increased respiratory muscle strength - intercostal muscles + diaphragm increase strength, allows greater expansion, therefore more air volume breathed in.

Increase O2 + CO2 diffusion rate - greater capillarisation muscles + alveoli allows O2+CO2 to diffuse rapidly (steeper diffusion gradient), can train longer and harder if more O2 available.

Maximal breathing rate increases - enables more air to move in and out of the lungs allowing for  more efficient gas exchange

Increased lung capacity - therefore allowing a greater quantity of air to move in and out.

Increased tidal volume - the amount of air breathed in and out per breath

Increased pulmonary ventilation (VĖ) - the amount of air breathed in and out in a minute

Greater capillarisation - enables more blood to flow in and out of the lungs to provide a greater surface area for haemoglobin to bind with the blood

Increased number of alveoli enables more gas exchange to occur 

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Lung Volume Key terms

Pulmonary Ventilation total volume of gas / air inspired (breathed in) or expired (breathed out) per minute - Resting volume 6-9 L/min

Residual Volume Amount of air left in the lungs after fully exhaling  - volume = 1 / 1.5 L

Tidal Volume - Volume of air breathed in and out with each breath - volume 0.5L

Inspiratory reserve volume - after normal T.V. amount of extra air that can be inhaled - volume 3L

Vital capacity - volume forced out of lungs after max inhale - volume 4.8L

Total lung volume - lung capacity after maximal inhale - volume 6L

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Mechanics of Breathing


  • External intercostals contract and internal intercostals relax
  • lift the ribs/thoracic cavity up and out 
  • diaphragm contracts / flattens
  • increase the size / decrease the pressure of the thoracic cavity


  • External intercostals relax and internal intercostals contract
  • pull the ribs/thoracic cavity down and in
  • diaphragm relaxes / rises
  • decrease the size / increase the pressure of the thoracic cavity

DURING EXERCISE - (use) greater force, further, more

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Gaseous Exchange

O2 / CO2 /gas moves from high / pp / Partial pressure to low pp / Partial pressure

At Alveoli

  • PPO2 (Partial Pressure of Oxygen) / concentration / levels of oxygen in the alveoli is high
  • PPO2 (Partial Pressure of Oxygen) concentration / levels of oxygen in the blood is low
  • This creates a steeper diffusion gradient / oxygen diffuses quicker
  • oxygen moves from the alveoli into the blood 
  • There is a low ppCO2 in the alveoli
  • There is a high ppCO2 in the blood
  • Because CO2 produced as by-product of aerobic respiration.
  • Causes diffusion gradient
  • CO2 diffuses from blood into alveoli and is expired
  • Steeper diffusion gradient created during a race so body’s gas exchange becomes more efficient 
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Immediate effects - when training at altitude (above 3000 m)

  • Possible altitude sickness, unable to train, limiting improvements to respiratory system
  • reduced PPO2, less oxygen available for respiration, leads to hypoxia
  • Decreased air pressure causes increase in breath frequency
  • PPO2 in air is less, therefore oxygen supply to alveoli is less
  • Reduced diffusion gradient of oxygen at alveoli, less oxygen diffuses into blood
  • Less oxygen combines with haemoglobin, less oxygen transported in blood
  • Reduced diffusion gradient of oxygen at muscle tissue
  • Performance at altitude deteriorates, fatigue quicker

Long-term effects

  • Increase in EPO levels
  • Increased number red blood cells, greater capacity carry oxygen
  • Increased concentration gradient oxygen at sea level
  • Exercise longer without fatiguing
  • Improved recovery times after exercise
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Neural Factors

Increased CO2 produced by body from exercise

CO2 dissolved in blood detected by chemoreceptors

these send message to medulla oblongata / respiratory control centre / RCC

responds sending nervous signals to respiratory system to increase tidal volume / depth and breathing rate / frequency

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  • Exercise induced asthma / asthma attack
  • wheezing whilst breathing and coughing
  • feeling of tightness in the chest
  • inflamed bronchi narrowed airways
  • reduction in the amount of air able to get into the lungs.


  • air breathed swimming is warm and moist reducing chance of asthma attack
  • exercise strengthens respiratory muscles
  • increase in vital capacity reduces effects of asthma.
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