Control of Breathing Flashcards
Basic elements of the respiratory control
Sensors - chemoreceptors, lung, other
Central controller - brains stem respiratory center
Effectors - respiratory muscles
Components of the respiratory center
Pontine respiratory center - apneustic area, pneumonia area
Medullary respiratory center - Ventral respiratory group, dorsal respiratory group
Dorsal Respiratory Group function
Controls the frequency of inspiration.
Activates respiratory muscles, via the phrenic nerve by action potential released in 2s bursts.
Inactivation of these neurons allows for passive expiration.
Ventral Respiratory Group function
Fire during inspiration with input from the DRG, and are recruited during forceful expiration.
Pneumotaxic area
Modulates the apneustic center and sends inhibitory signals to the DRG to shorten inspiration.
Activation increases the breathing rate, but absence has no effect.
Apneustic area
Stimulates the DRG t prolong inhalation but is overridden by the pneumotaxic area.
Apneustic breathing = long inspiration and short expiration.
Central chemoreceptors
On the ventral surface of the medulla for minute to minute control. Respond to changes in CSF pH.
Peripheral chemoreceptors
In the aortic arch and bifurcation of the common carotid arteries. Increase ventilation in response to lowered PO2, increased PCO2, and decreased pH.
Response of central chemoreceptors to pH
Low pH, increase breathing.
High pH, decrease breathing.
Effect of breathing low O2
Alveolar Po2 decreases, arterial Po2 decreases.
Sensed by peripheral chemoreceptors - fire muscles.
Ventilation increases.
Effect of increasing arterial PCO2
pH increases in the arteries and in the CSF
Peripheral and central chemoreceptors are activated.
Respiratory muscles contract and ventilation increases.
PCO2 returns to normal, pH follows suit.
Response to increases in plasma proton concentration
Increases pH is sensed by peripheral chemoreceptors, medullary respiratory neurons act.
Muscles contract increasing ventilation
Alv PCO2 decreases, Art PCO2 decreases and pH returns to normal.
Irritant receptors
Rapidly adapting pulmonary stretch receptors.
Inhaled dust, smoke, etc, in trachea and large airways.
Myelinated vagal afferents are stimulated and the response is to increase airway resistance - reflex apnea and cough.
Slowly adapting pulmonary stretch receptors
Respond to mechanical stimulation by lung inflation. Myelinated vagal afferent stimulated, and expiration becomes long and slow.
COPD patients with inflated chests.
Juxta-alveolar capillary receptors
In the alveolar walls, activated by engorgement of the pulmonary capillaries with blood. Acts to increase interstitial fluid volume - increases breathing rate - dyspnea.
Causes; left heart failure, blood back-ups,
Input to DRG
Peripheral chemoreceptors via the glossopharyngeal and vagus nerve.
Mechanoreceptors via the lung vagus nerve.
