Control of Ventilation Flashcards
what controls breathing
brainstem
what two groups of nuclei in the brainstem control breathing
- medullary group (rhythmicity centre)
- pontine group (apneustic, pneumotaxic)
what is the input of breathing into the brainstem
vagus and glossopharyngeal nerve
what does the dorsal and ventral resp groups control
dorsal resp group: insipratory
ventral resp group: inspiratory/expiratory
what is the function of dorsal resp group neurons
inspiratory neurons that discharge during inspiration and stop discharging during expiration
how do DRG initiate inspiration
with a weak burst of action potentials which gradually increase then stop (RAMP signal) –> breathing pacemaker
what do the DRG signals innervate
phrenic nerve supply of the diaphragm
how does DRG communicate with ventral resp grou
relays to VRG which stimulates muscles of expiration (intercostals, abdominal muscles) during heavy exercise
what neurons do VRG contain
both inspiratory and expiratory neurons
what is the function of VRG
drive neurons innervating intercostal or abdominal muscles (heavy exercise)
inactive during normal quiet respiration
what is the function of apneustic centre
sends stimulatory stimuli to inspiratory neurones
what is the function of nucleus of the solitary tract (NST)
essential for processing and coordination of resp and sympathetic responses to hypoxia
first synaptic station of cardiorespiratory afferent inputs (including peripheral chemoreceptors, baroreceptors and pulmonary stretch receptors)
what is the function of pneumotaxic centre
control cessation of inspiratory ramp signal from DIG
what is hypoactivation of pontine resp centres
prolonged deep inspiration
what is hyperactivation of pontine resp centres
shallow inspiration
what is the function of the pre-botzinger complex
houses pacemaker neurons
responsible for resp rhythm generation –> central pattern generator (CPG)
identify the structures in the brainstem
what are the neurotransmitters that the NTS respond to
receiving the excitatory drive involes glutamate, ATP and acetylcholine
what are the functions of central chemoreceptors
respond to increase in arterial PCO2
signals processed and information passed on to neuronal clusters in brainstem involved in generating breathing
ventilation increases to restore PCO2 levels
where are central chemoreceptors located
in brainstem
how do changes in PCO2 have changes on ventilation
hypercapnic response increases ventilation
plays major role in moment to moment control of breathing
how do central chemoreceptors respond to increase CO2 (hypercapnia)
through increases in H+ concentration
CO2 + H2O <–> H2CO3 <—> HCO3- + H+ <—> H+ + CO3^2-
decreases the pH –> activates central chemoreceptors to stimulate ventilation
where is the location of the central chemoreceptors
unclear
the retrotrapezoid nucleus (RTN) may be most critical
it sends signals to central pattern generator (CPG) in medulla
what are peripheral chemoreceptors
small, highly vascularized bodies in region of aortic arch and carotid sinuses
how do peripheral chemoreceptors send their info
glossopharyngeal nerve
vagus nerve
where do peripheral chemoreceptors send their info to
nucleus tractus solitarius (NTS) in the brainstem
what do peripheral chemoreceptors monitor
PO2, PCO2, [H+]
what occurs when PO2 decreases
firing rate of peripheral chemoreceptors increases –> goes to the NTS in brainstem –> increases ventilation
what do respiratory mechanoreceptors respond to
detect movement of lung and chest wall
are activated when lung inflates
what occurs when resp mechanoreceptors are activated
neural signals sent via vagus nerve to NTS in brainstem –> ventilation adjusted
summarize this
what are the effects of altitude
acute hypoxemia causes hyperventilation by activation of peripheral chemoreceptors
increases PaO2 and decreases PaCO2
what are the longer term adjustments to higher altitude (4)
- production of more erythrocytes
- decreased affinity of oxygen for Hb due to increase 2,3 - DPG (bohr shift to right)
- increase in pulmonary surface area
- increased capillary density in muscle
what is brisket disease
high altitude pulmonary hypertension (HAPH)
chronic alveolar hypoxia –> leads to hypoxic vasoconstriction and remodelling of pulmonary circulation
leads to right-sided heart failure
edematous fluid accumulates in ventral portions of chest –> brisket
what is the effect of exercise on ventilation
increase after onset is intially rapid but then steady state reached
PO2, PCO2, and pH remain relatively constant
