Cerebral Spinal Fluid: The Water of Life

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The brain produces roughly 500 mL of cerebrospinal fluid per day. This fluid is constantly reabsorbed, so that only 100-160 mL is present at any one time.

The entire surface of central nervous system is bathed by a clear, colorless fluid called cerebrospinal fluid (CSF). The CSF is contained within a system of fluid-filled cavities called ventricles.

Neurogenesis is dependent on the CSF. New neurons are created and travel in the CSF. [ [i] ] Hydration is the key to the CSF. [ [ii] ]

Ependymal cells of the choroid plexus produce more than two thirds of CSF. The choroid plexus is a venous plexus contained within the four ventricles of the brain, hollow structures inside the brain filled with CSF. The remainder of the CSF is produced by the surfaces of the ventricles and by the lining surrounding the subarachnoid space.

CSF Flow

Circulation of CSF. CSF (gray) is secreted by the choroid plexus present in the cerebral ventricles and by extrachoroidal sources. It subsequently circulates through the ventricular cavities and into the subarachnoid space. Absorption into the venous blood (dark orange) occurs through the arachnoid villi in the superior sagittal sinus and along the optic, olfactory and spinal nerve sheaths

From: Blood—Cerebrospinal Fluid Barrier Cover of Basic Neurochemistry Basic Neurochemistry: Molecular, Cellular and Medical Aspects. 6th edition. Siegel GJ, Agranoff BW, Albers RW, et al., editors. Philadelphia: Lippincott-Raven; 1999. Copyright © 1999, American Society for Neurochemistry.

CSF serves several purposes:

1.  Buoyancy: The actual mass of the human brain is about 1400 grams; however, the net weight of the brain suspended in the CSF is equivalent to a mass of 25 grams. The brain therefore exists in neutral buoyancy, which allows the brain to maintain its density without being impaired by its own weight, which would cut off blood supply and kill neurons in the lower sections without CSF.

2.  Protection: CSF protects the brain tissue from injury when jolted or hit. In certain situations such as auto accidents or sports injuries, the CSF cannot protect the brain from forced contact with the skull case, causing hemorrhaging, brain damage, and sometimes death.

3.  Chemical stability: CSF flows throughout the inner ventricular system in the brain and is absorbed back into the bloodstream, rinsing the metabolic waste from the central nervous system through the blood–brain barrier. This allows for homeostatic regulation of the distribution of neuroendocrine factors, to which slight changes can cause problems or damage to the nervous system. For example, high glycine concentration disrupts temperature and blood pressure control, and high CSF pH causes dizziness and syncope. To use Davson’s term, the CSF has a “sink action” by which the various substances formed in the nervous tissue during its metabolic activity diffuse rapidly into the CSF and are thus removed into the bloodstream as CSF is absorbed.

4.  Prevention of brain ischemia: The prevention of brain ischemia is made by decreasing the amount of CSF in the limited space inside the skull. This decreases total intracranial pressure and facilitates blood perfusion.

5.  Clearing waste: CSF has been shown by the research group of Maiken Nedergaard to be critical in the brain’s glymphatic system, which plays an important role in flushing metabolic toxins or waste from the brain’s tissues’ cellular interstitial fluid (ISF). CSF flushing of wastes from brain tissue is further increased during sleep, which results from the opening of extracellular channels controlled through the contraction of glials cells, which allows for the rapid influx of CSF into the brain. These findings indicate that CSF may play a large role during sleep in clearing metabolic waste, like beta amyloid, that are produced by the activity in the awake brain.

6.  Endocrine medium for the brain: the CSF serves to transport hormones to other areas of the brain. Hormones released into the CSF can be carried to remote sites of the brain where they may act.

Typical Cerebrospinal Fluid (CSF) and Plasma Concentrations of Various Substances

SubstanceCSFPlasmaCSF/plasma ratio
Electrolytes (mEq/l)
  Na+1381381.0
  K+2.84.50.6
  Cl−1191021.2
  HCO−322240.9
  Ca2+2.14.80.4
  Mg2+2.31.71.4
  PO3−40.51.80.3
Metabolites (mM)
  Glucose3.35.00.7
  Lactate1.61.01.6
  Pyruvate0.080.110.7
  Urea4.75.40.9
  Creatinine0.090.140.7
Amino acids (μM)
  Alanine26.03500.1
  Arginine22.480.90.3
  Aspartic acid0.22.00.1
  Asparagine13.51120.1
  Glutamic acid26.161.30.4
  Glutamine5526410.9
  Glycine5.92830.02
  Histidine12.379.80.2
  Isoleucine6.276.70.1
  Leucine14.81550.1
  Lysine20.81710.1
  Methionine2.527.70.1
  Ornithine3.873.50.1
  Phenylalanine9.964.00.2
  Phosphoethanolamine5.45.11.0
  Phosphoserine4.28.30.6
  Serine29.51400.2
  Taurine7.677.20.1
  Threonine35.51660.2
  Tyrosine9.573.00.1
  Valine19.93090.1
Proteins (mg/l)
  Total protein35070,0000.005
  Albumin15536,6000.004
  Transferrin14.42,0400.007
  IgG12.39,8700.001
  IgA1.31,7500.001
  IgM0.67000.001
From: Constancy of the Internal Environment of the Brain
Basic Neurochemistry: Molecular, Cellular and Medical Aspects. 6th edition.
Siegel GJ, Agranoff BW, Albers RW, et al., editors.
Philadelphia: Lippincott-Raven; 1999.
Copyright © 1999, American Society for Neurochemistry

The Table below lists the researched substances that enhance the cerebral spinal fluid:

Substances that Enhance the Cerebral Spinal Fluid

CategorySubstanceReferences
Amino Acid
L-Glutamine1
Hormone
DHEA2


References:

[i] Neurogenesis at the Brain–Cerebrospinal Fluid Interface

[ii] Investigating Structural Brain Changes of Dehydration Using Voxel-Based Morphometry

Daniel-Paolo Streitbürger, Harald E. Möller, Marc Tittgemeyer, Margret Hund-Georgiadis,

Matthias L. Schroeter, Karsten Mueller Published: August 29, 2012 DOI: 10.1371/journal.pone.0044195

Dehydration confounds the assessment of brain atrophy, T. Duning, MD, S. Kloska, MD, O. Steinsträter, PhD, H. Kugel, PhD, W. Heindel, MD and S. Knecht, MD

Dehydration affects brain structure and function in healthy adolescents

Effects of fluid ingestion on cognitive function after heat stress or exercise-induced dehydration


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