Components of control of Breathing
Cards (10)
- Origin of Breathing:
- The respiratory system has no intrinsic driving system like the heart
- It is therefore totally dependent on an external neural drive
- Origin of breathing occurs in respiratory control centres in brainstem
- In health breathing occurs automatically without conscious effort
- Purpose of Breathing:
- Purpose of breathing is to provide adequate alveolar ventilation
- O2 delivery
- CO2 excretion
- Alveolar ventilation alters in response to changing environmental or metabolic demands
- E.g. Exercise
- Adequate alveolar ventilation is essential to maintain a neutral acid-base balance
- Respiratory Control Centres (RCC):
- Respiratory control centres are situated in brainstem (medulla and pons)
- Medullary respiratory centre
- Provides output to respiratory muscles
- Pontine respiratory centres
- Influence output from medullary respiratory centre
- Interaction of these centres establish and modify respiration
- Higher Brain Centres - Other brain centres can influence Respiratory Control Centres (RCC):
- Cerebral cortex
- Cortical input can over-ride intrinsic breathing pattern from RCC
- Voluntary pathways synapse with AHC in spinal cord
- Directly stimulate respiratory muscles
- Necessary for speech eating coughing
- Hypothalamus / Limbic systems
- Pain and emotional state can modulate RCC
- Clinical Failure of Respiratory Control Centre (RCC):
- Hypoventilation or absent ventilation
- Brainstem CVA or tumour
- Increased intracranial pressure
- Decreased level of consciousness
- Alcohol
- Drugs
- Pharmacology
- Central sleep apnoea
- Hyperventilation
- Breathing dysregulation syndrome
- Components we need to breathe:
- Respiratory Control Centres
- medulla
- pons
- higher centres
- Effectors
- respiratory muscles
- Sensors
- chemoreceptors
- other lung receptors
- Clinical Failure Effectors:
- Neuromuscular disease
- Nerves (phrenic nerve)
- Neuromuscular junction (myasthenia gravis)
- Muscles (muscular dystrophy)
- Chest wall dysfunction
- Kyphoscoliosis
- Obesity
- Sensors:
- Chemoreceptors
- Central
- Peripheral
- Lung
- Stretch receptors
- Irritant receptors
- J receptors
- Other
- Proprioceptors
- All sensors feedback to Respiratory control centre to increase or decrease tidal volume or respiratory frequency
- What stops you holding your breath indefinitely?
- CO2 Levels!
- CO2 is an acidic gas which must be kept within normal range to allow cellular function
- CO2 levels are constantly sampled and monitored by chemoreceptors
- Advantages of CO2 based ventilatory system:
- CO2 production is related to O2 consumption
- CO2 production is related to pH
- CO2 has linear relationship to ventilation