topic 8 pt 2

• What affects the size (volume) of the thorax?

  The action of the respiratory muscles
• How do respiratory muscles change the volume of the thoracic cavity?

  They contract and relax

  
• What drives the activity of the respiratory muscles?

  Nerve impulses from the respiratory brain centres

  
• Which brain structures are involved in controlling respiration?

  The medulla oblongata and pons

  
• What happens to lung pressure as volumes change according to Boyle's Law?


  The pressure in the lungs changes
• Where are respiratory nuclei located?

  In the medulla oblongata and pons

  
• What are the components of the Medullary Rhythmicity Centre?

  • Dorsal Respiratory Group (DRG)
  • Ventral Respiratory Group (VRG)
• What is the role of intercostal nerves during forced expiration?

  They control internal intercostal muscles

  
• What do pinal nerves control during forced expiration?

  Abdominal muscles

  
• What does the Medullary Rhythmicity Centre drive?

  The basic rhythm of breathing
• What are the functions of the Dorsal Respiratory Group (DRG) and Ventral Respiratory Group (VRG)?

  • DRG: Mostly active during inspiration (diaphragm)
  • VRG: Dominant respiratory centre, active during laboured breathing, contains the pre-Bötzinger complex (pacemaker)
• How long does inspiration last according to the pacemaker?

  2 seconds
• How long does expiration last according to the pacemaker?

  3 seconds
• What happens to inspiratory cells after 2 seconds?

  They become inactive
• When do expiratory neurons become active?

  During high ventilation rates
• What is the role of the Pontine Respiratory Group (PRG)?

  It integrates sensory information about lung inflation
• How does the PRG influence inspiration?

  It sends inhibitory impulses to switch off inspiration
• What is the main goal of respiration?

  To maintain correct levels of respiratory gases in the blood
• What is the main chemical stimulus for breathing?

  CO2

  
• What is the principal stimulus for breathing derived from CO2?

  [H+]

  
• What happens when there is a slight increase in PCO2?

  It stimulates central chemoreceptors to increase respiration

  
• Where are central chemoreceptors located?

  Within the medulla oblongata
• What do peripheral chemoreceptors respond to?

  Changes in blood [H+]
• What is the location of peripheral chemoreceptors?

  In the carotid and aortic bodies

  
• What triggers peripheral chemoreceptors to stimulate inspiratory neurons?

  Large decreases in PO2 levels

  
• At what PO2 level do peripheral chemoreceptors trigger nervous impulses?

  Below 60 mmHg
• Why does the hypoxic drive only come into effect in unusual circumstances?

  Because blood haemoglobin is still 90% saturated at PO2 = 60 mmHg
• What happens when there is an increase in arterial PCO2?

  It stimulates central chemoreceptors to increase respiration

  
• What occurs when there is a decrease in arterial PCO2?

  Respiration runs at its normal pace
• What are the major regulatory mechanisms of ventilation?

  • Central chemoreceptors
  • Peripheral chemoreceptors
  • Medullary Rhythmicity Centre
  • Pontine Respiratory Group