Control of Ventilation Flashcards
why do we need O2 and why do we need to remove CO2
O2 - requirement for generating ATP through oxidative phosphorylation
CO2 - by product of respiration - helps produce bicarbonate buffer
what is the equation for minute ventilation
Ve = breathing frequency (f) x tidal volume (VT)
5 L/min = 10 breaths per min x 500ml per breath
why is the actual minute ventilation 3.5L/min at rest
due to dead space as reduces ml per breath from 500 to 350
amount of breathing varies due to what
activity vs rest
altitude
disease
how does do exercise affect breathing rate
O2 consumption ca increased 10 fold
how does altitude affect breathing rate
less O2 in the air so need to work harder to maintain O2 supply
why are smokers better suited for high altitude
bodies already adapted to hypoxic state
how / what diseases affect amount of breathing
pulmonary and cardiovascular diseases which compromise gas exchange or delivery
sleep apnoea
opioid depression
chronic hypercapnia
what are the three main classes of receptors for respiratory centres
lung
chemo
other
what are the types of lung receptors
pulmonary stretch receptors
cough or irritant receptors
J receptors
what are the type of chemoreceptors for respiration
central - ventral surface of medulla
peripheral - carotid bodies and aortic arch
what are some other respiration receptors
nasal and upper airway
muscle stretch receptors
joint proprioceptors
arterial baroreceptors
what are the respiratory centres that control automatic breathing
medulla: inspiratory and expiratory areas
pons: apneustic and pneumotaxic areas
cortical control of voluntary breathing can override respiratory centre control
which are the targeted efferents for breathing
diaphragm - phrenic 345
intercostal muscles
abdominal muscles
accessory muscles in neck and shoulder
where are the two respiratory centres in the brain
medulla - primary centre
pons - regulates medulla
what is the pathway from the pons to the medulla and to output respiratory muscles
Pontine respiratory group - pneumotaxic centres triggers the apneustic centre
both these areas target the DRG
the DRG then stimulates both the VRG (mainly expiration) and respiratory muscles
what is the nerve signalling in quiet breathing at rest
inspiratory nerve centre - DRG and some from VRG fire phasicly
but there is no expiratory nerve activity
what is the process that occurs between the VRG and the DRG
reciprocal inhibition
what can cause inhibition of inspiratory activity
therapeutic drugs = opiates, barbiturates
hypoxia
inhibition of blood supply
what factors or sensors provide information to the respiratory sensors
pain/emotional stimuli in the brain higher brain cortical voluntary control stretch receptors in the lungs irritant receptors in the lungs peripheral chemoreceptors in the carotid artery and aorta receptors in muscles and joints central receptors in the midbrain
what higher brain centres influences breathing
cortical:
voluntary hyperventilation - hypocapnia alkalosis
voluntary breathing holding - hypoxia - unsustainable
hypothalamic:
emotions - anxiety / pain
sensory reflexes - pain/cold
how do pulmonary stretch receptors affect breathing
afferent fibres from smooth muscle of bronchi and trachea
run in the vagus nerve to the respiratory centre in the medulla
inspiration inhibits the DRG and activates the VRG
(stop over inflation of the lungs)
how do irritant / cough receptors affect breathing
receptors in airways that initiate expiration through cough
afferent fibres run in the vagus to reparatory centre
also found in nose and upper airways
local anaesthetics prevent these being triggered when a tube passes down
how do muscle / joint receptors and proprioceptors affect breathing
muscle spindles rich in intercostals - few in diaphragm
activated by stretch associated with contraction of breathing - induced motion which can influence ventilation
what are baroreceptors in affecting breathing
sense blood pressure can influence ventilation
increase blood pressure = decrease in ventilation
what do J-receptors do
juxtacapillary
close to capillaries around alveolar wall - activated by traumas such as pulmonary oedema - this triggers ventilation
how do central chemoreceptors affect breathing
specialised region close to medulla respiratory centres but also close to rice blood supply
sensitive to CO@ and H+
H+ cannot cross the blood brain barrier but CO2 can which informs levels of H+
rise in CO2 stimulates receptors in the medulla from the CSF and increases ventilation
what are carotid and aortic bodies sensitive to
hypoxia - low O2
hypercapnia - high CO2
acidosis - high H+
what is the primary sensory of hypoxia
glomus cell attached to afferent nerve
hypoxia triggers Ca influx into glomus cell which trigger release of transmitters which innate action potential in afferent nerve
dopamine is one transmitter released bu the excitation is from ATP and ACh
