CHAPTER XXXIII 



THE REGULATION OF BREATHING 



THE movements of respiration are regulated by a centre which has 

 been localized in the medulla oblongata. This localization has been 

 made by watching the effects upon respiration of removal of the brain 

 from above downwards and from below upwards. By this means it 

 is found that, when an area of grey matter in the floor of the fourth 

 ventricle is damaged, all signs of respiratory movement completely 

 cease. To this centre run afferent nervous paths from various parts 

 of the body, and also from the higher nervous centres; from it pass 



Impulses (+and-) 

 from cerebral cortex. 



Impulses (.-) from nostrils 

 Impulses (- or +) from skin. 

 Impulses(-)frorn larynx 



Impulses from lungs limiting 

 excessive inspiration and(?) 

 .excess/re expiration 



^-Artery taking 

 blood to centre. 



'ntercostals. 



To diaphragm. 



To accessory muscles 

 in laboured breathing. 



Fia. I.j4. DIAGRAM ILLUSTRATING REGULATION OF RESPIRATION. 

 (+) signifies increased breathing; ( - ) diminished or inhibited breathing. 



efferent channels to the muscles concerned in breathing. Such fibres 

 do not pass directly from the centre to these muscles, but form a 

 synapse with the anterior horn cells in the spinal cord, from which 

 the effector nerves to the muscles of respiration arise. Thus the 

 diaphragm is supplied by the phrenic nerve, which arises from the 

 third, fourth, and fifth cervical nerves; the intercostal muscles from 

 corresponding branches of the intercostal nerves. 



Since the movements of breathing persist after all the afferent 



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