respiratory: control of ventilation Flashcards
part of brain responsible for neural control of ventilation
brainstem: medulla, pons, midbrain
what respiratory nuclei does the medulla contain
dorsal respiratory group in nucleus tractus solitarius
ventral respiratory group containing nucleus ambiguus and retroambigualis
pre-botzinger and botzinger complex near nucleus retrofacialis
what is pre-botzinger complex’s function
respiratory rhythmogenesis
what does DRG do
contains only inspiratory neurons that fire just prior to and during inspiration
ramp-like activity (steady increase and abrupt cessation)
controls depth/rate/pattern of breathing
input from chemo and mechanoreceptors in lung via CN X & IX & spinal cord
activity relayed to phrenic nerves
inhibits expiratory neurons in VRG and pontine respiratory group
what does the pons contain?
pontine respiratory group, which is made of pneumotaxic centre (inhibits inspiratory phase, allowing expiration) and apneustic centre (prolongs inspiration)
pneumotaxic centre comprises of nucleus parabrachialis and kolliker-fuse nucleus
components of Central pattern generator, what influences these components
pons: pneumotaxic centre, apneustic centre
medulla: VRG, DRG
higher centres (temp/emotion) influence pons
chemo receptors/mechanoreceptors influence medulla
what happens if smooth muscle of bronchial walls are stimulated
inspiration is shorter/shallower
next inspiratory cycle is delayed
whats hering-breuer reflex
inflation inhibits inspiration-> prevents over inflation, only present when adults take huge breaths
deflation reflex
deflation augments inspiration
juxtapulmonary receptors location/effects/stimulants
in alveolar walls close to capillaries
causes apnoea/rapid shallow breathing/bp and hr fall/skeletal muscles relax/larynx constricts
stimulated by increased alveolar wall fluid/oedema/pulmonary congestion/histamine
irritant receptors location/effects/stimulants
throughout airways between epithelial cells
trachea-> cough; lower airways-> hyperpnoea; bronchial and laryngeal constriction
responsible for deep breaths every 5-20 mins at rest-> reverse slow collapse of lungs during quiet breathing
stimulated by irritant gases/smoke/dust /rapid inflations and deflations
proprioceptive afferents location/stimulants/importance
respiratory muscles
stimulated by shortening and load of respiratory muscles
important for coping with increased load-> optimal tidal volume and frequency achieved
what do pain receptors do
brief apnoea-> increased breathing
trigeminal region (nose) and larynx
apnoea, spasm, increased hr, sneezing
arterial baroreceptors
stimulation inhibits breathing
how ventilation is affected by alveolar pco2
at low levels of co2, ventilation rate plateaus out->
increases linearly with increasing levels of co2-> at 9kpa of pco2 respiratory centre is depressed-> ventilation rate drops
how does pH change ventilation graph
acidosis-> leftward shift-> hyperventilation (blow off excess co2)
alkalosis-> righward shift-> hypoventilation
how do o2 levels affect ventilation? how does hypercapnia affect the graph? what’s so special about hypoxia + hypercapnia?
ventilation decreases with increasing o2 levels;
below 8kpa, o2 dissociates from haemoglobin-> body compensates for this by increasing ventilation below this level of oxygen
when o2 levels are too low-> respiratory centre is depressed
hypercapnia results in rightward + upward shift
hypoxia +hypercapnia are synergistic -> increase ventilation (gap between normal graph and hypercapnic graph increases as environment becomes more hypoxic)
where are chemoreceptors in brainstem ?
ventrolateral surface of medulla, at exit of CNX and cnix
how is pH affected in brain
central receptors detect
[h] proportional to pco2 from blood
inversely proportional to hco3- from CSF
CSF has little protein-> no buffering of pH-> small rise in pco2 causes large change in pH
how do central chemoreceptors respond to prolonged hypercapnia; example of disease
ventilatory drive falls-> CSF pH returns to normal
eg chronic respiratory disease
how do central chemoreceptors respond to altitude
CSF initially alkaline due to hypoxia-> increased ventilation
after days/weeks, CSF returns to normal and drive increases
what are 2 peripheral chemoreceptors? what cells are they made of and what are their properties? what are their functions?
carotid/aortic bodies;
type I: glomus (rich in NT; in contact with axons)
type II: sheath cells (enclose glomus cells);
fire when pco2/H+ increases
fire when po2 decreases
chyne-stokes respiration
rapid breathing-> long pause -> o2 saturation oscillates
caused by heart failure/stroke/altitude sickness
central sleep apnoea causes
can’t breathe: neuromuscular eg muscular dystrophy/phrenic nerve damage/disease
wont breathe: brainstem damage/disease
