Cerebrospinal fluid is separated from the body by what is known as the blood-bra
ID: 55157 • Letter: C
Question
Cerebrospinal fluid is separated from the body by what is known as the blood-brain barrier. Yet changes in arterial PCO2 cause a proportional response in cerebrospinal fluid PCO2. Why is this?
A. The cells forming the capillaries in the brain contain CO2 channels which allow CO2 into the CSF via diffusion.
B. The cells forming the capillaries in the brain contain CO2 channels which allow CO2 into the CSF via facilitated diffusion.
C. CO2 is actively transported into the CSF using ATPase pumps.
D. CO2 is not restricted by capillary barriers.
Explanation / Answer
Ans . Option C - CO2 is actively transported into the CSF using ATPase pumps.
The H+ formed in the CNS in CO2 hydration is actively exchanged for plasma Na+ utilizing the Na-K ATPase pump. This is the mechanism of CO2 transport in CSF which is the reason levels of arterial PCO2 to cause a proportional response in cerebrospinal fluid PCO2.