Generation of Respiratory Rhythm Flashcards
effect on breathing of removal of cortex and upper pons
slow gasping breaths
effect on breathing of removal of pons
return to rhythmic breathing
effect on breathing of removal of medulla
breathing stops
what aspect of breathing does the cortex control
voluntary breathing
what aspect of breathing do the pons, medulla and spinal cord control
automatic breathing
what groups in the brainstem help control automatic breathing
pontine respiratory group (PRG)
ventral respiratory group (VRG)
dorsal respiratory group (DRG)
what are medullary neurones
VRG, DRG
expiratory neurones
what do expiratory neurones do
inhibit inspiratory neurones
what do inspiratory neurones do
activate expiratory neurones
causes contraction of inspiratory muscles
what is the effect of inspiratory neurones during large inspirations
large activation of expiratory neurones
what is the effect of expiratory neurones during large inspirations
causes contraction of expiratory muscles
things that change the basic breathing pattern
inhaled noxious substances
speech/volition
sleep
exercise
feedback inputs - lung receptors
slowly adapting receptors
rapidly adapting receptors
c-fibre endings
all have afferent nerve fibres carried in vagus nerve
feedback inputs - chemoreceptors
central chemoreceptors
peripheral chemoreceptors
effect of vagal nerves cut on breathing
slow, deep breaths
effect of vagal nerves stimulated on breathing
shallow, rapid breaths
slowly adapting lung receptors
aka stretch receptors
mechanoreceptors situated close to airway smooth muscle
stimulated by stretching of airway walls during inspiration
help initiate expiration and prevent overinflation of lungs
initiate hering-breuer inflation reflex (prolonged inspiration produced prolonged expiration)
afferent fibres = myelinated
rapidly adapting lung receptors
aka irritant receptors
located in airway epithelium
primarily a mechanoreceptor so respond to rapid lung inflation
respond to chemicals (e.g. histamine), smoke, dust
RARs in trachea and large bronchi initiate cough, mucus production, bronchoconstriction
afferent fibres = myelinated
c-fibre endings
bronchial c-fibre endings in airway epithelium
unmyelinated nerve fibres
stimulated by increased interstitial fluid (oedema) and various inflammatory mediators (histamine, prostaglandins, bradykinins)
pulmonary c-fibre endings close to pulmonary capillaries - aka juxtapulmonary capillary receptors, J-receptors
peripheral chemoreceptors response to arterial o2 and co2
fast response to:
arterial pO2
arterial pCO2
arterial H+
central chemoreceptors response to arterial o2 and co2
slow response to arterial pCO2
oxygen terminology
above normal = hyperoxia
normal = normoxia
below normal = hypoxia or hypoxaemia in blood
carbon dioxide terminology
above normal = hypercapnia
normal = normocapnia
below normal = hypocapnia
what happens when pCO2 crosses the blood-brain barrier
equilibrium: pCO2 + H2O <-> H+ + HCO3-
H+ detected by central chemoreceptors on surface of medulla which stimulate medullary rhythm generator
what does hypoxia and co2 buildup result in
chronic hypercapnia
what does chronic hypercapnia result in
loss of sensitivity of central chemoreceptors
drugs and respiration - depressants
anaesthetics - almost all
analgesics - opioids
sedatives (anti-anxiolytics, sleeping tablets) - benzodiazapines (diazepam, temazepam, etc)
clinical examples of respiratory depressants
recreational drug overdose, procedural sedation
drugs and respiration - stimulants
primary action - doxapram
secondary action - beta-2-agonists (bronchodilators)
upper airway muscle activity - phasic
contraction of upper airway muscles
opening of upper airway
facilitates inward airflow
similar to activity in diaphragm/external intercostals which generate inspiration
upper airway muscle activity - tonic
continuous background activity
tends to maintain patent airway
varies with state of alertness
similar to activity in skeletal muscles which maintain posture
obstructive sleep apnoea
common
fragments sleep causing daytime sleepiness
important cause of traffic accidents
risk factors - obesity, alcohol, nasal obstruction, anatomical anomalies
