Cerebrospinal fluid and blood brain barrier Flashcards
what 3 structures help stabilize neurons in the CNS?
BBB, choroid plexus, CSF
what is continuous with CSF?
interstitial fluid
what contains the brain?
cranial meninges
what are the 3 layers of the crainal meninges?
dura matter
arachnoid matter
pia matter
which layer of the meninges has CSF?
arachnoid mater
what are the series of chambers in the CNS called?
ventricles
what are ventricles filled with?
CSF and ependymal cells
how many ventricles are there?
two lateral ventricles
third ventricle
4th ventricle
how are the ventricles connected in the brain and spinal cord?
brain - aqueducts
spinal cord - central canal
what are ependymal cells?
line brain surface, ventricles, and choroid plexus
what are the 3 main functions of ependymal cells in the CNS?
- proliferation -> stem cells -> new neurons and glial cells in brain
- produce CSF from plasma
- form and circulate CSF
what can disrupting the movement of the cilia on the brain do?
affect movement of CSF
what is the circulation of CSF
intraventricular foramina -> third ventricle -> cerebral aqueduct -> forth ventricle -> lateral and median apertures -> subarachnoid space -> arachnoid granulations in superior sagittal sinus -> venous circulation
where does removal of CSF occur?
sagittal sinus
how is CSF removed through the sagittal sinus?
CSF absorbed across arachnoid villi into venous circulation by drainage into lymphatic vessels
where is the dorsal sagittal sinus located?
between two hemispheres of the brain
is the removal of CSF pressure dependent - how?
yes - pressure of CSF is greater than low pressure venous system
what does the pressure difference between the CSF and venous system create?
bulk one-way flow of fluid
what is hydrocephalus?
increased CSF volume in skull associated with increased intracranial pressure
what is non-communicating hydrocephalus?
blockage of CSF movement through cerebral aqueduct or lateral/media apertures
what is another name for non-communicating hydrocephalus?
internal hydrocephalus
what is communicating hydrocephalus?
impairment of absorption into the dorsal sagittal sinus
what is another name for communicating hydrocephalus?
external hydrocephalus
what is a treatment for hydrocephalus?
ventriculo-peritoneal shunt
where is the pressure increasing in internal hydrocephalus?
ventricles expand -> pressure inc
where is the pressure increase in external hydrocephalus?
outside of the brain
what are the two locations of a spinal tap?
cisterna magna
subarachnoid space in lumbar spina column
when collecting CSF for a suspected lesion where do you collect?
whichever site it closest to the suspected lesion
which is riskier cisterna magna or lumbar spinal column for a spinal tap?
cisterna magna - risk of cerebella herniation
what does CSF analysis asses?
inflammatory processes
what is CSF formed by?
choroid plexus
what is formed by selective movement of solutes across BBB?
CSF and brain interstitial fluid
what creates the osmotic gradient for water to be taken into the CSF?
inward flux of Na, HCO3, and Cl
what are the components of the BBB?
endothelial cells
basement membrane
glia
what are the cell to cell connections in the BBB?
tight junction
adherence junctions
desmosomes
what is the BBB ineffective against?
substances that can diffuse through the plasma membrane ex. steroid
Brain capillaries consist of ________ linked by _________ that interact with ________ and _________ to selectively control movement of materials into the brain
Brain capillaries consist of endothelial cells linked by tight junctions that interact with astrocytes and pericytes to selectively control movement of materials into the brain
where is the BBB absent?
certain areas that need to monitor chemical composition of blood and release hormones to the body - vomiting center and hypothalamus
what are the selective entry mechanisms of the BBB?
diffusion of lipid soluble substances
receptor mediated transport
what are lipid soluble substances that can diffuse into the brain?
ketone bodies - energy source for brain during starvation
CO2 - inc protein conc. in brain interstitial fluid
what is responsible for low level basal glucose uptake into the BBB in endothelial cells and astrocytes?
GLUT1
what is a high affinity isoform that is main present in neurons that will facilitate movement of glucose?
GLUT3
what is P-glycoprotein?
transports large lipophilic molecules out of CSF
what is another name for P-gp?
MDR1
what drug temporarily inhibits the BBB?
amitriptyline
what are macrocyclic lactones?
avermectins and milbemycins
broad antiparasitic
why cant collies have ivermectin?
MDR1 has a mutation that allows ivermectin pass BBB -> ivermectin binding to GABA channels impairing signaling -> neurological symptoms
compare CSF and blood serum
low K+ and fewer larger proteins
similar osmolarity
