CONTROL OF BREATHING

1
CONTROL OF BREATHING

• AIMS
• What are the neural control mechanisms?
• What are the chemical control mechanisms?
• What are the mechanical control mechanisms?

2
NEURAL CONTROL

• AUTOMATIC
• RESPIRATORY CENTRES
• Pons (pneumotaxic)
• Medulla (VRG EI, DRGI, Oscillator)
• Active for Inspiration
• Evidence from transection electrical recording
• VOLUNTARY CONTROL
• Separate pathway
• Temporary interruption of automatic
• Behavioural conditions

3
CHEMICAL CONTROL

• CO2 O2 - stimulated breathing
• Chemical sensors- chemoreceptors
• Peripheral- (aortic carotid bodies)
• large blood flow
• transmitter substances
• nerve supply
• aortic arch and carotid sinus
• sensitive to O2 lack
• also to H, CO2
• fast response
• Central- (neurones in 3 areas on surface of
  medulla)
• separated from blood by ECF, CSF BBB
• poorly buffered due to low proteins
• slow but stronger response
• sensitive to CO2, H and pH
• very high CO2 can be depressive, also very low O2

4
MECHANICAL CONTROL

• HERING- BREUER (1868)- nerves in smooth muscle of
  Bronchi and Trachea- LUNG INFLATION INHIBITS
• IRRITANT REFLEXES- nerves in bronchioles, larynx,
  trachea SNEEZE, COUGH
• J-RECEPTORS-nerves(c fibres- alveolar, bronchial
  walls)- chemical or mechanical stimuli
• NON- PULMONARY - immersion effect, muscle and
  joint receptors ( muscle spindle, golgi tendon
  organs) swallowing and vomiting

5
overview
6
CONCLUSIONS

• 1. Neural control involves automatic output from
  respiratory centres, modified by input from
  chemical, mechanical voluntary factors.
• 2. Chemical control at rest is dominated by CO2
  H, with O2 important in hypoxia.
• 3. Mechanical control involves afferant
  information from lung receptors and also from
  muscles and joints