<prompt> Total amount of CNS in CSF ?100-150ml300-350 ml500-550 ml600-650ml  <response>: Ans. is a i.e., 100-150 mlThe major source of CSF is the choroidal plexus of all 4 ventricles, mainly in two lateral ventricles.Other sources of CSF are ependymal cells of the ventricles and the brain itself, perivascular spaces.The total volume of CSF in an adult is about 125-150 ml.The rate of formation of CSF is about 500-550 mlday. Thus the CSF is replaced 3-4 times every day. 