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IPHY 3430 9-29-11
Review session this Thursday, 7:30
Regulation of respiration
Homeostatically regulated variables:
P02, PCO2, and pH
Why pH?
H20 + CO2 ---> H2CO3 ---> HCO3- +- H+
Sensors: chemoreceptors in carotid and
aorta, plus more in the brain (central
chemoreceptors).
Most sensitive to: PCO2 and pH
Least sensitive to: PO2
Input to medulla from Pons
Apneustic Center
prevents inspiratory neurons from being switched off,
thus lengthening inspiration
Pneumotaxic Center
switches off inspiratory neurons, thus shortening
inspiration
These centers allow input from higher centers in the brain,
plus probably some chemoreceptor input
Output of Medulla:
Dorsal respiratory group: motor control of
inspiratory muscles for inhalation at rest
Ventral respiratory group: motor control of
inspiratory and expiratory muscles during
exercise
PreBötzinger complex (medulla): pacemaker
activity for respiratory rhythm.
Input to medulla (probably via pons)
A. higher brain centers (talking, hold
breath, etc)
B. chemoreceptors in brain and
periphery
C. vagus input from stretch receptors in
lungs (Hering-Breuer reflex)
Regulation
 blood PCO2
 blood pH, PO2 ---> chemoreceptors--->
(pons-medulla) --> motor output -->
 rate and depth of breathing --->
 alveolar PCO2 and  PO2-->
 blood PCO2 and  blood pH and PO2
Regulation
 blood PCO2
 blood pH (PO2) ---> chemoreceptors--->
(pons-medulla) --> motor output -->
 rate and depth of breathing --->
 alveolar PCO2 and  PO2-->
 blood PCO2 and  blood pH (PO2)