Cerebrospinal fluid & the blood-brain barrier Fluids of the CNS Cerebrospinal fluid & the blood-brain barrier

Meninges Membranous coverings of the CNS Layer of 3 tissues Protects nervous tissue and provides support and cushion

Meningitis Bacterial meningitis results when a bacterial infection of the meninges Produces increased cranial pressure May produce seizures & unconsciousness

Cerebrospinal fluid (CSF) In the space between the middle meninge & that closest to the CNS tissue Circulates through the ventricles & to the brainstem CSF allows the CNS to float in a cushion of fluid Provides shock absorption http://www.obfocus.com/images/csf.gif

Nutrients for the CNS The CSF provides nutrients & energy and acts to eliminate waste. Glucose is the brain’s only energy source.. O2 is required cellular respiration Brain receives 12-15% of the total blood supply. Brain injury - most commonly results from depleted O2 supply.

Blood-brain barrier Group of mechanisms that regulate the flow of chemicals between CSF & the blood. blocks/decreases entry of toxins. few chemicals/molecules are allowed to pass through. Immune system molecules have limited access Mostly Lipid molecules

Ease of passage Lipid soluble substances pass through more easily. Water soluble substances pass through slowly & can linger in the fluid.

Membrane transport proteins Allows substances that are NOT lipid soluble to pass in & out of the barrier. Move required substances in, like glucose. Move waste out.