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Flashcards in Control of Breathing Deck (28)
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pulmonary mechanoreceptors

slowly adapting pulonary stretch receptors (PSR or SAR)

irritant or rapidly adapting pulmonary stretch receptors (RAR)




peripheral chemoreceptors - carotid bodies and aortic bodies

central chemoreceptors - potentially at several locations in the CNS


slowly adapting pulmonary stretch receptors

located in airway smooth muscle

large, myelinated fibers

activated by lung inflation or bronchoconstriction


consequences of PSR activation

Breuer-Hering reflex

abdominal expiratory muscle activation



Breuer-Hering reflex

facilitates expiration

terminates inspiration if VT elevated

prolongs expiration (slows breathing)

happens when lung inflation is 3x the Vt


irritant or rapidly adapting pulmonary stretch receptors

stimulated by inhaled irritants and rapid large inflation

located between airway epithelial cells

have somewhat smaller myelinated fibers than PSR

activation causes airway protective reflexes


protective reflexes resulting from RAR activation

increased respiratory rate

bronchoconstriction - may contribute to bronchoconstriction triggered by histamine in asthma

facilitate cough/zneeze - may be dedicated cough receptors

elicit increased mucus production and a rapid, shallow breathing pattern that increases turbulant flow



located in close proximity to the alveoli and stimulated by edema

also located within airway epithelium and stimulated by inhaled irritants

elicit rapid, shallow breathing pattern

may contribute to the sensation of dyspnea


What activates C-fibers?

left heart failure

interstitial lung disease


pulmonary embolism


A-delta fibers

recently identified neurons in guinea pigs that can elicit cough

termed cough receptors, give rise to myelinated axons with lower conduction velocities of about 5 m/sec


peripheral chemoreceptors

carotid and aortic bodies

stimulated by decreased PaO2, increased PaCO2, and decrase pHa

PaO2 rather than arterial O2 content provides stimulus

peripheral chemoreceptors not directly stimulated in anemia


central chemoreceptors

on/near ventrolateral surface of medulla and other CNS sites

a subset localized to the retrotrapezoid nucleus, which is the rostral end of the ventral respiratory column in the medulla

other sites in the brain stem

responsive to increases in PaCO2 or decreases in pHa

NOT responsive to changes in PaO2

most responsive to PaCO2 because of the blood-brain barrier


other inputs on breathing

muscle spindles in respiratory muscles

tendon organs and joint receptors

arterial baroreceptors - inhibit ventilation

metabolic factors - exercise, hormone levels

cortical factors - sleep, stress, etc.


ventilatory responses to PCO2 and PO2

ventilation can double with a 2mmHg increase in PaCo2

hypoxia augments the ventilatory response to hypercapnia

hypercapnia or acidosis augments the ventilatory response to hypoxia


effect of chronic changes in PaCO2

compensatory increase in arterial bicarbonate that leads to an increase in kidney retention of bicarbonate over a period of days

brain bicarbonate will also increase even though it does not readily cross the blood-brain-barrier

increased bicarbonate "resets" the medullary chemoreceptors

CO2 sensitivity is reduced as a result


central pattern generator (CPG)

a neuronal circuit within the CNS that can produce a patterned motor behavior such as breathing, locomotion, vocalization, or chewing without requiring phasic sensory feedback

phasic sensory input may modify the motor output but is not essential for generating the basic motor pattern


ponto-medullary respiratory neurons

dorsal respiratory group (DRG)

ventral respiratory column (VRC)

pontine respiratory group (PRG)


Dorsal Respiratory Group (DRG)

found within nucleus of the solitary tract (NTS)

processing of respiratory afferent input from cranial nerves IX and X


ventral respiratory column (VRC)

forms a continuous column in the ventrolateral medulla extending from around the facial nucleus to the medullary spinal junction

includes the retrotrapezoid nucleus (RTN) and the PreBotzinger complex (preBotC)


pontine respiratory group (PRG)

located int he rostral dorsolateral pons with the parabrachial and Kulliker-Fuse nuclei

responsible for the coordination of the respiratory control system with other systems such as the cardiovascular control and pain

also responsible for coordinating with higher brain functions such as emotions

major relay between brainstem and forebrain to control breathing


Retrotrapezoid nucleus (RTN)

central chemoreceptor


PreBotzinger complex (preBotC)

inspiratory rhythm generation


parafacial respiratory group (pFRG)

hypothesized to be important for expiratory rhythm generation


rostral ventral respiratory group (rVRG)

inspiratory premotor neurons


caudal ventral respiratory group (cVRG)

expiratory premotor neurons


Cheyne-stokes breathing

decrease in sensitivity of central chemoreceptors

decreased cardiac output - leads to increased delay between change in PACO2 and detection of change by chemoreceptors

patient experiences periods of sleep apnea as a result


Congenital Central Hypoventilation Syndrome (CCHS)

potentially life-threatening genetic disorder that involves hypoventilation, especially during sleep due to an impaired ventilatory response to PCO2 and PO2

also asosciated with functional impairments of the autonomic nervous system and tumors of neural crest derivatives

defining mutation is a polyalanine expansion in Phox2b

appears to result in a loss of retrotrapezoid neurons


Rett Syndrome (RTT)

dvelopmental disorder of the central nervous system resulting from mutationsin the X-linked gene methyl-CpG-binding protine 2

usually seen in girls

results in severe neurological symptoms that include speech and movement disorders as well as irregular breathing (Cheyne-Stokes)