Respiratory Control Flashcards
Describe the NTS (nucleus tractus solitarius) and its role in respiratory control.
Long nucleus, runs length of medulla dorsally and medially. Receives affernets from many thoracic and abdominal viscera.
Caudally, contains the Dorsal Respiratory Group (DRG) , vast majority of neurons here discharge with inspiration
Where is the Ventral Respiratory Group and what is its function?
Anatomically, corresponds with nucleus ambiguus and the retroambigualis. (ventral and lateral to NTS)
rostral VRG is largely inspiratory
-external intercostals, upper airway muscles receive
input from here
caudal VRG is largely expiratory
-activates expiratory muscles with inputs from timing
and afferent sensory info
Where is the Pontine Respiratory Group and what is its function?
Pons, depending on where you record you can get a region where the neurons fire during inspiration, expiration, and the transition between the two.
stimulating PRG cuts inspiration off; sometimes termed pneumotaxic center due to ability to inhibit inspiration; crucial in determining length of inspiration and preventing apneusis (stuck in inspiration)
What is the Botzinger Complex?
Corresponds to the facial nucleus anatomically, lies just rostral to the VRG, most neurons here are expiratory
What is the Pre-Botzinger complex and why is it important?
Contains a wide variety of discharge times: inspiration, expiration, and the transition between both
postulated as the site for respiratory rhythm generation by pacemaker neurons.
What does the Dorsal respiratory Group do?
95% of the neurons in the region fire during inspiration are pre-motoneurons (upper motoneurons) that send their axons down the spinal cord to activate the motoneurons of the phrenic nerve.
takes timing info about inspiration, afferent info about lungs and gas levels and determines how big a breath we need to take
What is the primary source of drive to the phrenic nerve?
DRG
What relays the drive to the phrenic nerve and upper airway muscles?
the rostral VRG
What relays the drive to the expiratory muscles?
the caudal VRG
How do the DRG and VRG produce a pattern of breathing to match conditions?
by using their sensory inputs
What constitutes chemical control of breathing?
PO2, PCO2, and pH
Where are the central chemoreceptors found and what is their role?
Found on ventral medullary surface , have rostral, intermediate, and caudal regions. Rostral and caudal are directly chemosensitive, meaning their neurons change firing rate in direct response to a change in the chemical composition of the surrounding fluids.
What is the adequate stimulus of the central chemoreceptors?
The direct stimulus is H+ in the CSF. The source of this hydrogen ion is the CO2 dissolved in the plasma.
Carbonic anhydrase is found in the CSF (on the cell membranes of the central chemoreceptor neurons (or near them). (3)CO2 will combine with water (of the CSF) in the standard reaction and dissociate into H+ and HCO3 –> H+ will stimulate chemoreceptors to increase firing rate and thus drive to breathe, trying to bring back normoxic conditions
Where are the peripheral chemoreceptors found and what is their role?
Found in the carotid body and aortic arch, respond to O2 levels. Carotid body receptors are far stronger in their effect.
adequate stimulus: CO2 (directly), pH, O2, all in plasma
mechanism: high blood flow, can use dissolved PO2, uses dopamine as neurotransmitter; ability to sense O2 is directly tied to ability to use it, discharge rate increases with decreasing PO2
Which respond faster to acute changes in arterial CO2, central or peripheral chemoreceptors?
Peripheral, increase minute alveolar ventilation
