Summary of Year A Level PE Physiology Topics


Respiratory Summary

Lung volume or capacity


Average values at rest (litres)

Changes during exercise

Tidal volume

Volume of air breathed in or out per breath



Inspiratory reserve volume

Volume of air that can be forcibly inspired after a normal breath



Expiratory reserve volume

Volume of air that can be forcibly expired after a normal breath


Slight decrease

Residual volume

Volume of air that remains in the lungs after maximum expiration


Remains the same

Vital capacity

Volume of air forcibly expired after maximum inspiration in one breath


Slight decrease

Minute ventilation

Volume of air breathed in or out per minute


Big increase

Process of breath

  • Drawn in through nasal cavity
  • Phayrnx-larynx (voicebox)
  • Epiglottis covers the trachea
  • Move to trachea
  • Mucus/cilia filter air
  • Left/right bronchus
  • Secondary bronchi
  • Bronchioles
  • Alveolar air sacs

Gaseous Exchange

  • Partial pressure is the pressure exerted by a gas in a mixture of gases
  • PP of O2 in lungs -100
  • PP of O2 in capillaries- 40
  • Oxygen removed by working muscles
  • Lower blood concentration= lower PP
  • Bigger diffusion gradient= faster diffusion
  • CO2 diffuses in reverse
  • Pressure will be equal by end of diffusion

Factors promoting diffusion into blood

  • Alveoli/capillary permeability (1 cell thick)
  • Alveoli--capillary short distance
  • Haemoglobin high affinity for oxygen
  • Alveoli large surface area

Diffusion @ muscle

  • Combines through diffusion with oxyhaemoglobin
  • Transferred to mitochondria

Exercise's application

  • Sustained exercise necessitates aerobic glucose breakdown
  • This requires more oxygen
  • PP of O2 ++ in muscle
  • Steeper diffusion gradient/increased rate
  • More CO2 byproduct


  • Inspiration = increased thoracic cavity --reduced air pressure
  • Inspiration= intercostals contract --diaphragm contracts and flattens, ribs pull up/out
  • Expiration= decreased thoracic cavity--- increased air pressure
  • Expiration=Passive at rest/relaxation

During Exercise

  • Sternocleidomastoid lifts sternum
  • Scalenes and pectoralis minor help lift ribs up and out (deepen breath)


  • Internal intercostals (ribs down/in)
  • Abdominals- diaphragm UP

Control of Breath

At rest- Inspiratory Centre sends nerve impulse to diaphragm

  • External ICS (Phrenic nerve) cause contraction
  • Elastic recoil and muscle relaxation cause expiration

During exercise there are 3 main areas of change


  • ++ CO2 in blood===+++ blood pH
  • Chemoreceptors sense this and signal increase in depth of breath
  • Stimulation of extra inspiratory muscles


  • +++motor centre activity
  • Stimulation of proprioceptors
  • Baroreceptors detect blood pH  and increase breathing RATE
  • Increased body temp

Receptors--medulla oblongata--phrenic nerve--respiratory muscles

Expiration during Exercise

  • Expiration is passive at rest  due to elastic recoil of lungs
  • During exercise we expel greater volume of air in a very short time
  • So we stimulate expiratory muscles
  • The sequence is

Receptors-->Medulla Oblongata-->Intercostal Nerve-->Expiratory Muscles (Intercostals/abdominals)


  • Reduces lung capacity caused by swelling and narrowing of lungs airways
  • Smokers cough- cigarette smoke damages cilia lining the trachea and bronchi which help to remove mucus from the lungs
  • Damages the alveoli which impairs gaseous exchange
  • Carbon monoxide from cigarettes binds more easily to haemoglobin than O2, therefore reducing O2 carrying capability

Role of adrenaline

Brain sends signal to adrenal glands

  • Release of adrenaline into the blood stream
  • Adrenaline stimulates the sympathetic


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