Lp 54 Flashcards
Bilateral aggregates of neurons in the medulla & pons
-dorsal respiratory group (DRG)
-ventral respiratory group (VRG)
-pontine respiratory centres
-rhythm-generating & integrative centre
-contains inspiratory & expiratory neurons
-inspiratory neurons excite the diaphragm & external intercostal mm via the phrenic & intercostal nn, respectively
-expiratory neurons end those excitatory signals
VRG
-cyclic on/off activity repeats continuously
-respiratory rate of 12-15 breaths per minute
-normal respiratory rate & rhythm= Eupnea
-inspiratory phase: ~2 sec
-expiratory phase: ~3 sec
VRG
-integrates input from peripheral stretch and chemoreceptors
-stretch: detect lung inflation
-chemo: detect Co2, O2, H+ levels in arterial blood
-sends the information to the VRG
-not well understood
DRG
-influence & modify activity of medullary neurons
-smooth out transitions from inspiration to expiration and vice versa
-fine-tunes breathing rhythm generated by VRG during certain activities
-receives input from higher brain centres and from peripheral sensory receptors
Pontine respiratory centres
Control of breathing automatic control governed by
-chemoreceptors
-stretch receptors
-irritant receptors
-most important
-sense changes in CO2- esp. midbrain
Central chemoreceptors
-monitor O2
-found in carotid aa & aorta
Peripheral chemoreceptors
Detect distension & promote expiration
Stretch receptors
-detect noxious gases, smoke, dust, cold air
-promote rapid, shallow breathing
Irritant receptors
-sympathetic stimulation
-strong emotions and pain results in stimulation of respiratory centres
Hypothalamus
-voluntary control of breathing bypasses brain stem control centres
-voluntarily modulate breathing at terns by conscious stimulation of respiratory mm
-ex. Holding breath, taking deep breath
-ability to hold breath is limited d/t rising CO2 levels
Motor cortex
-breathing is modified to meet changing demands
-O2 supplies not kept at a steady state
-reflexes ensue adequate oxygenation
-2 reflex responses are protective mechanisms
Reflexes
-irritants stimulate peripheral n receptors
-accumulated mucus
-dust
-noxious fumes
Signals are transmitted by CN X & activate respiratory centres
-irritants innate responses in an attempt to clear passageways: bronchoconstriction, coughing, sneezing
Pulmonary irritant reflex
-aka. Herring- Breuer reflex
-prevents excess stretching of lung tissue
-stretch receptors n visceral pleurae & larger airways are stimulated by excessive lung inflation
-initiate inhibitory signals to inspiratory centre
-inspiration is terminated
-expiration ensues
-thought to be more protective than a normal regulatory mechanism
Inflation reflex
