Control of Breathing Flashcards
what is breathing modulated by?
reflexes, volitional control, vocalisation, emotional events, physiological challenges
what must the neuronal control of breathing do?
establish automatic rhythm, respond to metabolic demands, respond to mechanical changes, range of episodic nonventilatory behaviours
what is eupnea?
normal rhythmic breathing
what is dyspnea?
being short of breath, unpleasant conscious awareness of difficulty breathing
what are the respiratory related neurons and what do they do?
array of interconnected neurons and they fire more action potentials during respiratory cycle
where is the central pattern generator and what does it do?
in the brainstem (medulla oblongata) and it independently generates respiratory rhythm
what do the respiratory motor neurons do?
innervate respiratory muscles, axons via the phrenic nerve innervate the diaphragm
what does the frequency of respiratory central pattern generator changes do?
strength of drive from central and peripheral receptors, change both depth and frequency of ventilation
what does the brain receive neural signals from?
chemoreceptors (feedback on blood PO2, PCO2 and pH) and mechanoreceptors (feedback on mechanical status of lungs, chest wall and airways)
what does the brain send neural signals to?
respiratory muscles (produce rhythmic breathing movements), upper airway muscles and produce reflexes to keep airways patent
what are chemoreceptors?
sensory receptors that detect chemical changes in the surrounding environment
what do chemoreceptors detect changes in with the blood?
PO2, PCO2 and pH
what are peripheral chemoreceptors?
small, highly vascularised bodies in region of aortic arch and carotid sinuses
what is information in the peripheral chemoreceptors sent via to get to the brainstem?
via the glossopharyngeal and vagus nerves to the nucleus in the brainstem called NTS
what is the NTS?
nucleus tractus sollitarius
what do peripheral chemoreceptors respond to
decreases in PO2 (hyoxia)
describe the mechanism of the peripheral chemoreceptors
reduction in arterial PO2 - peripheral chemoreceptors stimulated - neural signals sent from carotid and aortic bodies to the NTS in brainstem - ventilation increases to restore PO2 levels
at what level of arterial PO2 does progressive hyperventilation begin?
below 60mmHg
where does the hypoxic response originate?
in carotic and aortic bodies
what are central chemoreceptors?
clusters of neurons in the brainstem that are activated when PO2 is increased (hypercapnia) or pH decreased
describe the mechanism of central chemoreceptors
increase in arterial PCO2 - central chemoreceptors stimulated - signals processed and information passed on to neuronal clusters in brainstem involved in generating breathing - ventilation increases to restore PCO2 levels
where does the hypercapnic response originate?
in central chemoreceptors in brainstem
what are mechanoreceptors?
sensory receptors that detect changes in pressure, movement and touch
what do the mechanoreceptors detect in the respiratory system?
movement of lung and chest wall
what do mechanoreceptors detect during inspiration?
inflation of lungs and movement of chest
what is the role of the mechanoreceptors during inspiration?
pulmonary stretch receptors, can terminate inspiratory effort/prevent over inflation, adjust ventilation for changes in posture
describe the mechanism of mechanoreceptors
inflation of lungs activates mechanreceptors - neural signals sent via vagus nerve to NTS in brainstem - ventilation adjusted accordingly
what type of receptor is essential in adapting and adjusting breathing?
mechanoreceptors
what is the receptor location of mechanoreceptors?
airway smooth muscle or airway epithelium
what is the stimulus of mechanoreceptors in the smooth muscle?
inflation/distension of airway
what is the reflex of mechanoreceptors in the smooth muscle?
termination of inspiration
what is the stimulus of mechanoreceptors in the epithelium?
rapid lung inflation or deflation
what is the reflex of mechanoreceptors in the epithelium?
sigh
describe the integration of information in the brainstem
NTS receives information from mechanoreceptors and peripheral chemoreceptors- information processed in brainstem by respiratory neurons - cluster of respiratory neurons in brainstem generate rhythm of breathing (CPG) - rhythmic signal is sent to the respiratory muscles
when are the inspiratory neurons active?
during inspiration
when are the expiratory neurons active?
during expiration
what are respiratory rhythm generating neurons in the brainstem
bilateral cluster of neurons with rhythm generating properties
what are the two types of respiratory pattern generating neurons?
inspiratory and expiratory
describe the output from brainstem to respiratory muscles
brainstem neurons produce rhythmic output - rhythmic neural signals sent to spinal cord - phrenic nerve exits spinal cord at cervical spinal cord level 3-5 - phrenic nerve innervates diaphragm - nerves exiting thoracic spinal cord innervate intercostal muscles
what are the different respiratory groups in the brainstem?
pontine, ventral and dorsal
where does the dorsal respiratory group of the brainstem sit?
in around the NTS
what is the dorsal respiratory group composed of?
inspiratory neurons
what is the function of the dorsal respiratory group?
integration of sensory information from the respiratory system (from chemoreceptors and mechanoreceptors via CNXI and CNX)
what does the ventral respiratory group contain?
inspiratory and expiratory neurons, motor neurons (unlike DRG), contains regions which may be respiratory CPG
what is the function of the pontine respiratory group?
modulates respiratory output
what voluntary actions alter air flow?
breath holding, speaking and singing
where do the voluntary breathing actions originate from
the motor cortex in the cerebral cortex
what can be said about the control of voluntary breathing actions?
it is precise but not absolute as breath holding is overridden by ventilatory drive from chemoreceptors
what are the 2 main mechanisms of motor control?
cortical neurons send axons to the brainstem and cortical premotor neurons send axons to motor neurons which control the muscles of respiration
what do respiratory neurons in the brain do?
send neural signals to respiratory muscles to produce rhythmic breathing
