Moderate exercise being one of the most powerful stimulators of ventilation works by the way of

Moderate exercise doesnot reduce the aerial pO2, increase the aerial pCO2, or reduce the aerial pH. Option A: The brain, upon transmitting motor impulses to the exercising muscles, is believed to transmit collateral impulses into the brainstem at the same time to excite the respiratory center. This action is analogous to the stimulation of the vasomotor center of the brain stem during exercise that causes a simultaneous increase in aerial pressure. Option B: The pO2 of mixed venous blood does fall, but there are no known chemoreceptors that are stimualated as a result. Option C: Two points are impoant regarding pH during moderate exercise: pH = pK + log () The pH of the blood is dependent only on the ratio of the amount of CO2 to the amount of HCO3- The concentration of both buffer components (HCO3- and CO2-) are very large compared to the amount of H+ added to the blood during moderate exercise. Thus, any change in HCO3- due to the addition of H+ during moderate exercise remains constant. When sufficient oxygen is not available during exercise, there is increased accumulation of lactic acid, which initially leads to an increase in paCO2. However, this is counteracted by the stimulation for fuher lactic acid production and prevents a decline in blood pH. Thus, blood pH remains constant in moderate exercise. Ref: Guyton and Hall 26th edition Pgno: 645-667