Abstract: Neurons are exquisite sensitive to alterations. The brain has a high metabolic rate; thus, it requires rapid mobilization of nutrients and clearance of metabolites to maintain constant homeostasis in the environment around the neurons and glia. We discuss the normal ranges of metabolic products in the cerebrospinal fluid (CSF), blood and urine and the direction of nutrient supplement from blood to CSF. Furthermore, we summarize the clearance pathway of the metabolic products from CSF to urine. Body fluids, which take nutrients from others, discard metabolites to others and have a narrower normal range of metabolic products, have a higher homeostasis status. We suggest the cerebrospinal fluid has higher homeostatic priority than blood. Unlike CS For blood, which is kept stable by homeostatic mechanisms in which early changes associated with disease were removed, urine is an ideal source of changes that can reflect conditions of the brain, especially chronic conditions.
Published Date: 21 Jul 2016