respiratory 4 Flashcards
what generates respiratory rhythm
medullary respiratory centres
medullary respiratory centres receive input from
chemoreceptors
proprioceptors
airway receptos
hah centres
depth is determined by
depth is determined by how actively the respiratory centre stimulates the respiratory muscles
timing is determined by
when, and low long the respiratory centre is active
how many respiratory ce3ntres
5
respiratory centres
2 in the pons - pneumotaxic and apneustic
3 in the medulla - ventral and dorsal, and pre-botszinger
pre-botzinger complex
the pacemaker
for quiet tidal breathing
spontaneously discharging neuron
pre botzinger complex talks to
dorsal respiratory group which controls the phrenic nerve
emits repetitive bursts of inspiratory actin potentials - once these stop, expiration can happen
basic rhythm of quiet tidal breathing
when inspiratory area is active, diaphragm actively contracts
dorsal respiratory group receives input from
higher centres
pontine centres (bpneustic/pneumitaxic)
CNS and peripheral chemoreceptors
respiratory muscles
forced breathing
involves different inspiratory and expiratory muscles (not just phrenic nerve)
so Ventral respiratory centre does this
Ventral respiratory centre
inactive during quiet breathing
extra respiratory drive
contribute to expiration (major) and inspiration
NB during heavy exercise
pontine respiratory centres
influence/modify prebot/DRG?VRRG activity
coordinatore transition between inhalation and exhalation - smooth out transitions
apneustic area
inhibits inspiratory switch off - prolongs inspiration
longer inspiratory reduces respiratory frequency and increases depth
pneumotaxic area
limits inspiration
this increases respiration rate and decreases depth
decreased blood pH Amy indicate
CO2 retention
accumulation of lactic acid
excess ketone bodies (eg. diabetes mellitus)
how does pH effect respiration
CO2 receptors are next to the respiratory centres
direct pH in cerebrospinal fluid - medullary control
peripheral receptors - in arterial blood, only used when arterial blood has really low oxygen
central chemoreceptors
beneath ventral surface of the medulla
excites other portions of the respiratory centres - increase rate and depth of breathing
highly sensitive to changes in either CO2 or H+ in CSF
how does CSF get acidic
CO2 diffuses across the blood brain barrier, H+ does not
carbonic anhydrase is on the medulla surface
this converts CO2 into carbonic acid which liberates protons
regulation of ventilation
peripheral chemoreceptors
located in the carotid and the aorta arteries
specialised cells that sense hypoxaemia (major)
can also be affected by pH, pCO2, and temperature sensitive (minor)
aortic bodes
peripheral chemoreceptor
on aorta
send sensory info to medulla through vagus nerve
carotid bodies
peripheral chemoreceptor
at fork of common carotid artery
send info mainly through glossopharyngeal nerve
peripheral chemoreceptors react to
pO2
don’t get triggered until arterial pO2 in 60mmHg - severe hypoxaemia
hypothalamus and limbic system influence
modify rate/depth
eg. breath holding in anger or gasping in pain
increases in body temp cause increase in response rate
cortical controls - direct signals from the cerebral motor cortex that bypass medullary controls eg. voluntary breath holding
vagal airway receptors
upper
sense flow, temperature, pressure, muscle contraction, obstruction
myelinated pulmonary receptors
middle airway receptors
mechanoirritant - respond to irritation of the airways by initiating cough reflex or bronchoconstriction
non myelinated pulmonary receptors
lower receptors
stimulated by chemicals
airway defines reflexes - tachypnoea, mucous secretion
inflation reflex
hiring-breuer reflex
stretch receptors in airways that are dominant regulator of breathing
inhibitory signals to the medullary centres to end inhalation
acts as a protective response to prevent over inflation
cough reflex
larynx, carina, bronchi and trachea are very sensitive to light touch
- inspire
- close epiglottis, shut vocal cords
- contract abdominal/intercostals
- open epiglottis and vocal cords
- air explodes out and carries foreign matter
respiratory adjustments
adjustments are geared to intensity and duration
brain - psychological stimuli - anticipation of exercise, cortical motor activation
proprioceptor impulses
