PHYL3002 Lecture Notes - Lecture 3: Intracellular Ph, Hyperpnea, Hypopnea
LECTURE THREE: Control of Ventilation
Control of Ventilation:
• Complex
• Brainstem generates base rhythm and has central chemoreceptors
• Peripheral chemoreceptors
• Lung receptor
• Upper airway receptors
• Muscle proprioception
• Multiple muscles → not just respiratory muscles, perform other
functions
• Voluntary and automatic pathways
Rhythm Generation:
• Rhythmogenesis → located within medulla oblongata
• Section between medulla and spinal cord halts respiration
• 2 centers involved in rhythm generation → dorsal and ventral areas
• Dorsal respiratory group → back
o Receives afferent input
o Inspiratory cells to phrenic nerve
o Contains cells active in inspiration
• Ventral respiratory group → front
o Output to
▪ Accessory muscles
▪ Expiratory motor neurons
▪ Upper airway (NA)
▪ Vagus to ASM (NA)
o Classically cells active in expiration and some in inspiration
o Divisions not clear → perform other non-respiratory functions
The Rhythm Generator:
• 3 hypothesis about rhythm generation
• Oscillator, off-switch threshold and pacemaker kernel
• Oscillator and off-switch threshold are distributed network models
• Rhythm depends on delay between inhibiting active nerves
• Kernel model depends on pacemaker activity in single neurons
• Pacemaker neurons are located in the pre-Botzinger
• Some cells in pre-Botzinger complex show pacemaker AP spikes
• AP open voltage gated calcium channel allowing imaging
• All pacemaker cells act together
• Glutamate inhibitors block synchrony and respiratory rhythm
Central Modifications:
• Isolated medulla can generate a respiratory rhythm but not a normal
pattern
• Apenusis → prolonged inspiration with short expiration
• Pneumotaxic center in Pons shortens inspiration
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