Human Phys 6.9 Flashcards
What are the main tasks of the respiratory control mechanism?
To establish automatic rhythm for contraction of respiratory muscles
To adjust this rhythm and accommodate changes in metabolic demand, mechanical conditions, and a wide range of episodic, non-ventilatory behaviors
What are the main components of the control mechanism?
Control centers in the brain stem
(medulla and pons)
Chemoreceptors for O2 and CO2 (central and peripheral)
Mechanoreceptors in the lungs and joints
Respiratory muscles
What 3 groups of neurons control breathing?
Medullary respiratory center
Apneustic center
Pneumotaxic center
Where is the inspiratory center of the medullary respiratory center located?
Dorsal respiratory group
What does the inspiratory center of the medullary respiratory control?
Basic rhythm by setting frequency
What does the inspiratory center of the medullary respiratory send?
Motor output to the diaphragm via phrenic nerve
How can inspiration be shortened in the inspiratory center of the medullary respiratory?
Inhibition via pneumotaxic center
Apneusis
Prolonged inspirations separated by brief expirations
What does stimulated of the apneustic center in the lower pons produce?
Breathing pattern (excites the inspiratory center in the medulla)
What does the pneumotaxic center turn off?
Inspiration
Where is the pneumotaxic center located?
Upper pons
What does the pneumotaxic center limit?
Size of tidal volume and secondarily regulates RR
What is respiration drive stimulated by?
Brainstem
What inputs is the control of breathing modulated by?
Conscious inputs from the cortex
Influences from the limbic system and reticular activating system
Chemoreceptors
Metaboreceptors in muscle
Mechanoreceptors in lungs
Chemoreceptors
Sense changes in the chemical constituents of blood (primarily PCO2 and H+)
Hering-Breuer reflex
Reflex inhibition of inspiration triggered by pulmonary stretch receptors upon expansion of the lungs and mediated by the vagus nerve
Where are central chemoreceptors located at?
Brainstem and are the most important for minute to minute control of breathing
What do central chemoreceptors communicate with?
Inspiratory center
What is the central chemoreceptors extremely sensitive to?
Changes in pH of the cerebrospinal fluid
What do central chemoreceptors respond directly and indirectly to?
Directly to changes in pH
Indirectly to changes in PCO2
What does a low pH result in?
Hyperventilation
What does a high pH result in?
Hypoventilation
What do changes in O2 have no direct effect on?
Respiratory center (indirect effect via peripheral chemoreceptors)
Where are peripheral chemoreceptors for O2, CO2, and H+ found?
Carotid artery and aortic arch
What is the information from the peripheral chemoreceptors about arterial PO2, PCO2, and pH relayed to?
DRG via central nerves 9 and 10
When do peripheral chemoreceptors respond?
When PO2 < 60 mmHg
What happens if PO2 decreases < 60 mmHg?
Breathing rate is increased in a steep and linear fashion
What is the effect of decreased PCO2 less important than?
Response to decreased PO2
What does detection of reduction in PO2 lead to?
Increased breathing rate
What is decrease in arterial pH detected by?
On the carotid bodies
Lung stretch receptors
Mechanoreceptors in airway smooth muscles are stimulated by the distention of the lungs and airway
This initiates a reflex decrease in breathing rate and is called hering-breuer reflex
Joint and muscle receptors
Mechanoreceptors in the joints and muscles detect movement and stimulate the inspiratory center (they are important in the early ventilatory response to exercise)
Juxtacapillary receptors
Located in the alveolar walls and when stimulated by engorgement of pulmonary capillaries increases breathing rate
