PPoS: ventilation Flashcards
effect of sectioning below pons and medulla
apnoea: falt line
effect of sectioning above pons
eupnoea: normal breathing = central pattern generator
effect of sectioning between pons and medulla
gasping. short inspiration, long inspiration
effet of sectioning mid-pons, middle of 4th ventricle
apeneusis: long inspiration, short expiration
what is the pneumotaxic centre, where is it and what are the effects of disconnecting it
inhibits inspiratory phase
upper pons. disconnected leads to more time spent inspiring
what are the 4 main respiratory nuclei in medulla
dorsal respiratory group, ventral respiratory group, pre-botzinger complex and botzinger complex
what is the significance of PBC
key centre for respiratory rhythmogenesis
pscemaker
where are PBC and BC located
near nucleus retrofacialis (RTN)
where does DRG receive inputs from
from chemoreceptors and lung mechanoreceptors (relayed by IX and X cranial nerves and spinal cord)
what do DRG inspiratory neurones do
- inhibit expiratory neurones in VRG and pontine respiratory group (PRG) = pattern
- neural activity to phrenic nerves
- control depth and rate of breathing
- receptor info: override control
what does the cortex do
higher centre:
control ventilation
interrupts breathing pattern generated
what is the apneustic centre and what does it do
prolongs inspiration
absebce = gasping
where is DRG located
nucleus tractus solitarius NTS
what does the DRG do
- control insp
- fire along phrenic nerves to diaphragm: depth and rate of breathing
- insp neurones inhibit exp neurones in VRG and pontine rep group (PRG)
where does DRG receive inputs from
- chemoreceptors and lung mechanoreceptors (relayed by IX and X cranial nerves and spinal cord)
- higher brain centres - override
what does the VRG contain
nucleus ambiguosis NA
nucleus retroambiguosis RTN
site of juxtapulmonary receptors
alveolar, bronchial walls.
close to capillarues
what do J receptors cause
- aponea or rapid shallow breathing
- fall in HR and BP
- laryngeal constriction
- relax skeletal muscles
what are J receptors stimulated by
- increased alveolar wall fluid
- oedema
- pulmonary congestion
- microembolisms
- inflammatory mediators e.g. histamine
what reflexes do stretch receptors stimulate
- hering-breur inflation reflex: inflation inhibits inspiration
- deflation reflex: deflation augments inspiration
where are stretch receptors located and what do they do
- smooth bronchial wall muscle
- makes insp shorter and shallower
- delay next insp cycle
action of irritant receptors
Receptors in trachea lead to cough
those in lower airways hyperpnoea
Also reflex bronchial and laryngeal constriction
Responsible for deep augmented breaths seen every 5-20 mins at rest
location of irritant receptors
through airway between epithelial cells
stimulation of irritant receptors
Irritant gases, smoke and dust, inflammation, rapid large inflations and deflations, pulmonary congestion
site and stimulation of prorioceotive receptors
-resp muscles
-Stimulated by: shortening and load of
respiratory muscles (but not diaphragm)
- Important for coping with increased load, and achieving optimal tidal volume and frequency.
pain receptors
brief apnoea followed by increased breathing
receptors in trigemina region and larynx
apnoea or spasm, heart rate
nasal trigeminal nerve endings – sneeze reflex
arterial baroreceptors
stimulation inhibits breathing
whats the ventilatory response to CO2
equation of PACO2
negative feedback control mechanism
if alveolar vent halves, PACO2 doubles
PACO2 inversely proportional to rate of CO produced/alveolar vent
describe the combination hypoxia and hypercapnia
synergistic
combined effect is greater than sum of ind effects
where are chemoreceptors located
ventrolateral surface of medulla
near exit of C IX and X
describe what central chemoreceptors respond to
pCO2 from blood, [HCO3-] from CSF
equation for [H] at chemoreceptor
proportional to PCO2 / [HCO3-]
what is an adaptation of central chemoreceptors to prolonged hypercapnia
- CSF pH is normal (but arterial pCO2 is high)
- ventilatory drive decreases (inappropriate)
e. g. chronic resp disease
not relying on hypercapnic drive to breath, rely on hypoxic drive = DO NOT GIVE PATIENT O2
what is an adaptation of central chemoreceptors to altitude
- CSF initially alkaline due to hypoxic drive
- CSF pH will return to normal and drive decreases
where are peripheral chemoreceptors located and their innervations
aortic bodies - vagus nerve
carotid body - carotid sinus nerve (a branch of glossopharyngeal nerve)
what are the two main types of carotid bodies
- type 1 - gloms cells: many neurotransmitters, content axons which innervate them (carotid sinus nerve fibres)
- type 1 - sheath cells: enclose type 1 cells
function of peripheral chemoreceptors
-increase pCO2 and H increases ventilation
-decrease pO2 increases vent
(respond to hypercapnia, hypoxaemia and metabolic acidosis)
-v fast response - to oscillations in blood
