Respiratory Physiology Part Iii

Regulation of Respiration                                                                                                                                                                  

Overview

Respiration starts in the brain stem (has centers that regulate rate of inspiration and expiration) à project axons to motor neurons on the spinal cord à go to diaphragm or intercostals muscles à causes chest wall and lung to expand à changes alveolar Po2 and reduces alveolar Pco2 à diffusion across the membrane changing the arteriole Pco2

Regulation: there is feedback.

Brain stem centers involved in respiratory control:

Made of the pons, medulla which have the neurons for regulating respiratory rhythm

Motor neurons involved

Phrenic motor neurons (From cervical segments in the spinal cord)

Intercostals motor neurons (innervated by thoracic cords)

Larynx and pharynx (receive motor neurons from the medulla)

Apnea à transection b/w spinal cord and lower medulla so no breathing

Normal respiration à transection above the pons. There are abnormalities but an animal with this transection will be alive.

Medullary respiratory centers:  Dorsal respiratory group (generate rhythms for inspiration); ventral respiratory group (generate rhythms for expiration and inspiration); DIFFERENT from HEART—no respiratory pacemaker cells

Pons

Lower: apneustic center

A cut in b/w the lower and upper pons will give you a pattern of breathing called apneusis. Where the person spends a lot of time in inspiration.

Upper: pneumotaxic center

Inhibits the apneustic center so you get a normal pattern of breathing. The apneustic center will prevent it from doing the abnormal pattern.