Fig. 22From: Fluid and ion transfer across the blood–brain and blood–cerebrospinal fluid barriers; a comparative account of mechanisms and rolesTransport schemes for CO2 (a) and (b), and for HCO3 − (c) and (d). Transport of CO2 and HCO3 − can be distinguished since the latter but not the former entails the transport of net charge. By contrast transport of HCO3 − in one direction and transport of H+ in the other can produce the same net result. See text for further explanation. The proportion of CO2 transport that occurs by the mechanism in (b) is negligibleBack to article page