Which time points (W-Z) on the Cheyne-Stokes breathing graph are associated with the highest pCO2 of lung blood and highest pCO2 of the neurons in the respiratory centre?
Cheyne Stokesbreathing : When a person over-breathes, thus blowing off too much CO2 from the pulmonary blood while at the same time increasing blood O2, it takes several seconds before the changed pulmonary blood can be transpoed to the brain and inhibit the excess ventilation. By this time, the person has already over ventilated for an extra few seconds. Therefore, when the over ventilated blood finally reaches the brain respiratory centre, the centre becomes depressed to an excessive amount, at which point the opposite cycle begins--that is, CO2 increases and O2 decreases in the alveoli. Again, it takes a few seconds before the brain can respond to these new changes. When the brain does respond, the person breathes hard once again and the cycle repeats. Z: point after which respiration will sta as shown in graph. Due to apnoea till this point the PCO2 will become maximum in the lungs W: maximum excitement of respiratory centre due to maximum PCO2 in brain
Lung Blood Respiratory Centre X Y
`Lung Blood Respiratory Centre Y Z
Lung Blood Respiratory Centre Z W
Lung Blood Respiratory Centre W X
Respiratory System Pa 3