(iv) In a case of severe exercise, where there is belie acid accumulation the blood pH falls and this increases the respralory drrve

The oscillations, in some unknown way. produce respnaloiy drive which Iharefoie ASUS when the VT increases (as. in exeicisej. It is further believed Thai Ihe respiraloiyd live due To the oscillations mentioned above, occurs via the carotid and aortic chemoreceptors. (iv) In a case of severe exercise, where there is belie acid accumulation the blood pH falls and this increases the respralory drrve. ( v) During exercise, impulses descend via the pyramidal tract nerves aausing from Ihe cerebral cortex. According to one theory, collaterals of these nerves terminate on the respiratory center when These motor nerves are stimulated. these collaterals are also stimulated increase in VO E (vi) Pise of body temperature due to exercise may also be ,1 contributory factor Some negative answer at this stag*, may better be remembered For practical purposes it may be said, blood PCO2 and PO2 do not change with exercise therefore the hypervenlilaton ol exercise cannot be explained by assuming that there occurs hypoxia o* hypereapnea. further, excepting strenuous exercise, the lactic acid accumulation is not sufficient lo cause a fall of pH. Benefits of hyperventitation Together with the circulatory augmentation, it is the hyperventilation. that makes the additional demands (for 02 supply and C02 removal) to be met satisfactorily. ETABOLIC CHANGES A. Changes in general metabolism In Ihis issue. Ihe following will be discussed.