Choroid Plexus of the lateral & 3rd ventricles= blood supply from posterior & anterior chorodial arteries

Choroid plexus of the temporal horns and 4th ventricle= blood supply from superior and posterior inferior cerebellar arteries

Nerves= vagus, glossopharyngeal, and sympathetic nerves

smaller in diameter than other areas of body= 180 angstroms

exchange between the cerebral capillaries and the ECF is limited d/t high impermeability BBB

tight junctions (zonula occludens) resutrcits intracellular movements of molecules greater than 20 angstroms

Astrocyte foot processes surround capillaries 

High= Sodium, Chloride, Magnesium

Low= GLUCOSE, protein, AA, Uric Acid, postassium, Bicarb, Ca, Phos

Sodium is ALMOST the same cocentration as plasma 

0.35-0.4 ml/min (0.25% replaced q min)

500-600 ml/day

Turnover time for total CSF volume is 5-7 hours (QID)

40-70% enters through macroscopic spaces in CP

30-60% enters across the ependyma and pia 

Endothelium of CP does NOT posses tight functions--> fenestrated

Filtered blood that enters is called stroma--> creates hydrostatic pressure and bulk flow

60% results from oxidation of glucose by the brain

40% from ultrafiltration from cerebral capillaries

Glucose concentration is CSF is 60% of that in the blood

Ratio constatnt unless glucose rises to more than 270-360 

GLucose in blood enters CSF by faciliitated transport 

Limited movement into CSF

Permeability of BBB increases with age

Proteins that enter the brain are drained into the macroscopic pathways & cleared from the CSF space into the dural venous sinuses 

Minimal issue with CSF formation and ICP

Greater issue with formation and CPP

Increased ICP to 20 mmHg= no change in formation 

But if CPP < 70 mmHg= CSF formation decrease

Reduction of CPP accompanied by an increased ICP reduces CP BF and CBF more than just hypotension alone 

Entire brain and spinal cord has a capacity of 1600-1700 ml

150 ml of this capacity is occupied by CSF

CSF is found in ventircles of the brain cisterns around the outside of the brain, subarachnoid space around the brain and spinal cord

All chambers are connected and communicate and pressure is maintained at a constant level 

Cushions brain

provides patheway for nutrients

Regulates ions and other chemicals

Transports neurohormones and neurotransmitters

Brain flots in fluid that is almost equal in specific gravity 

Severe blow to the head the fluid on affected side is so incompressible that as the skull moves, the fluid pushes the brain at the same time in unison with the skull

On opposite of the head the sudden movement of the skull causes the skull to pull away from the brain momentarily d/t brain's inertia creating for a split second a vaccum space in the area opposite to the blow

When the skull is no longer being accelerated by the blow, the vaccum suddenly collapses and the brain hits the inner surface of the skull 

Formed at a rate of 500 ml/day 

2/3 originates from the choroid plexus in the 4 ventricles

95% for the two lateral ventricles

Small amounts by the ependymal surfaces by the arachnoidal membranes 

Fingerlike projections of arachnoidal membrane thru the walls and into the venous sinuses that function like valves allowing CSF to flow through while preventing backflow

Conglomerates of villi form arachnoidal granulations that protrude inot the sinuses 

Endothelial covering the villi have large enough to allow free flow of CSF, dissolved protein molecules, RBCs, WBCs into venous blood 

Large arteries and veins of the brain lie on the brain's surface, penetrate inward and cary layer of pia mater 

Pia is loosely adherent to the vessels so a space called perivascular space exists between it and each vessel

Perivascular spaces follow both the arteries and the veins into the brain as far as the arterioles and venules

No true lymphatics are present in brain tissue 

Perivascular spaces in effect are specialized lymphatic system for the brain. They also carry dead WBCs and debris away from the brain