CSF Flashcards
CSF Pathway
choroid plexus -> lateral ventricles -> interventricular foramina -> III ventricle -> cerebral aqueduct -> IV ventricle
- IV ventricle -> formen of Megendie -> cisterna magna -> superior cistern -> SAS
- IV ventricle -> 2 foramina of luschka -> pontine, interpeduncular, and chiasmatic cisterns -> SAS
SAS -> arachnoid villi -> superior sagittal sinus -> right transverse sinus -> sigmoid sinus -> internal jugular vein
CSF Production
70-75% secreted by choroid epithelia in
- lateral ventricles
- roof of III and IV ventricles
- two interventricular foramina
- two formania of Luschka
rest from extrachoroidal sources
- cerebral capillary walls
- H20 production via metabolism
Choroid Plexus
70-75% of CSF production
choroid plexus capillary, fenestrated
choroid plexus epithelium, tight junctions -> BBB
- ciliated - CSF circulation
- many mitochondria - active secretion
CSF Volume Distribution
140 mL total
- 30 mL in ventricles
- 80 mL in brain SAS
- 30 mL in spinal SAS
500 mL produced per day
replaced 3-4 times per day in order to
- remove harmful metabolites
- homeostasis of environment
CSF Functions
- remove harmful metabolites
- maintain constant environment for neurons, glia
- protection of CNS from trauma
- distribute neuroactive hormones
CSF Composition
CSF has
- less protein
- less K+, Ca2+, pH
- more Mg2+, Cl–, lactate, H2O
- equal Na+
CSF Appearance - Clear, Colorless
normal
CSF Appearance - Yellow, Bloody
hemorrhage
CSF Appearance - Protein > 150 mg/dl
bilirubin from plasma
CSF Appearance - Protein > 500 mg/dl
block in SAS by tumore, meningeal cancer, or other compressing lesion
CSF Appearance - WBCs
neuts = bacterial meningitis
lymphocytes = fungal
CSF Appearance - Decrease in Glucose
acute bacterial infection
CSF Appearance - Gamma Globulin
MS, inflammatory disorders
Hydrocephalus
“water in the brain” leading to increased intracranial pressure, enlargement of the ventricles at the expense of the surrounding brain
due to…
a) oversecretion of CSF = communicating hydrocephalus
b) impaired reabsorption of CSF = communicating hydrocephalus
c) obstruction in CSF circulation = noncommunicating hydrocephalus
Fluid Compartments and Barriers
(1) vascular, (2) CSF, (3) extracellular/interstitial
Blood-CSF Barrier
CSF-Brain Barrier
Blood-Brain Barrier
Blood-CSF Barrier
- formed by tight junctions of choroid epithelia
- important in the transport of nutrients that are needed in small amounts over long periords of time (VitC, Vit6, folates)
Blood-Brain Barrier
formed by
- tight junctions and continuous basement membrane of endothelial cells of brain capillaries
- perivascular foot processes of astrocytes
regulates diffusion of metabolites and metabolic products that the brain consumes rapidly (gluose, lactate, amino acids, ribonucleases)
- transport occurs via diffusion (lipid-soluble, hydrophobic), passive/active carriers, ion channels/exchangers
CSF-Brain Barrier
ependymal cells lining ventricles and intercellular space, no tight junctions, free bidirectional exchange
Failure of the BBB can occur with…
- primary tymors or metastasis (-> vasogenic edema)
- stroke or bacterial meningitis
- MS (T lymp enter and atttack myelin, brain, spinal cord)
- imflammation -> seizures, epilepsy
can exaccerbate neurological consequences of traumatic brain injury, HIV demementia, HTN, brain hemorrhage, and exposure to radiation or nerve gas
Types of Brain Edema
vasogenic
- increased permeability of BBB and capillaries -> increased brain ISF -> increased intracranial pressure -> smaller ventricles
- caused by stroke, ischemia, head trauma, meningitis, tumor
cytotoxic
- increased intracellular fluid volume (cell swelling) due to a failure of energy dependent mechanisms leading to accumulation of water inside cells -> decrease in brain ISF, increased intracranial pressure, reduction of ventricle size
- caused by drug poisoning, hyponatremia, water intoxication, hypoxia/ischemia
