CSF - Lecture 3 Flashcards
what is CSF
watery “broth” found in and around the brain and spinal cord
what does CSF form
a liquid cushion
gives buoyancy to the CNS organs
what happens with the brain floating
CSF reduces brain weight by 97%
prevents the brain from crushing under its own weight
what does the CSF also do
protects the brain and spinal cord from trauma
what does the CSF help with
nourish the brain
remove wastes produced by by neurons
what does CSF carry
chemical signals b/w different parts of the CNS
how much CSF is in the body
100-160 mL of fluid present in the body at one time
normal total volume of CSF
150 cc
what is CSF produced by
choroid plexus
@ a rate of about 20 cc per hour or 500 cc per day
how often is CSF changed
every 6-7 hours
what is the composition of CSF
similar to blood plasma
contains less protein and more sodium and chloride ions
how is CSF formed
cells actively secrete Na+ into the ventricular system in exchange for K+
sodium ions electrically attract Cl- and osmotically draw water from the blood vascular system to constitute CSF
where is most CSF formed
choroid plexus
membranes on the roofs of the four brain ventricles
where is the choroid plexus
hangs from the roof of each ventricle
what are the plexuses
clusters of thin walled capillaries
enclosed by a layer of ependymal cells
capillaries of the choroid plexus
fairly permeable
fluid filters continuously from the bloodstream into the ventricles
how are the cells in the choroid plexus joined
tight junctions
choroid plexus cells also have
ion pumps
allow them to modify filtrate by actively transporting only certain ions across their membranes into the CSF pool
what happens to CSF after it enters the ventricles
moves freely throughout the choroid plexuses
some CSF enters ______
canal of the spinal cord
where does most CSF go
enters the subarachnoid space through the lateral and median apertures in the walls of the fourth ventricle
what does CSF do in the subarachnoid space
bathes the outer surface of the brain and cord
CSF pressure in a human
150-180
what is CSF pressure regulated by
rate of absorption and rate of formation
