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31 Cards in this Set

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what are 2 ways (besides skull) that the brain is protected?
suspended by meninges
CSF
where are the bridging veins? what type of hematoma can lead lead to?
come off cerebral vessels in subarachnoid space and empty into superior sagittal sinus in space b/w 2 dura layers
rupture leads to subdural hematoma
how does a subarachnoid hematoma usually develop?
rupture of cerebral aa in subarachnoid space
what are the portions of the dura that divide the cerebral hemispheres? sep the cerebellum?
falx cerebri
tentorium cerebelli
what are arachnoid villi/granulations?
extensions of arachnoid into dura; drain CSF into venous system
what are the 2 dura layers?
meningeal (inner) and periosteal (outer)
how do you distinguish b/w epidural and subdural hematomas on radiograph?
epidural- lens shaped; fast bleeding and pooling of blood
subdural- crescent shape; slow bleeding
how do subdural hematomas usually present?
headaches
gradual, weeks after trauma
rupture of what aa. usually leads to an epidural hematoma?
middle meningeal a runs in epidural space and supplies meninges
what is the tentorial incisura and what is its significance?
tentorial notch
opening in the cranial cavity around midbrain
formed by dura
pressure in this area->compress CN 3 (ptosis, "down and out sx"
what are 3 dangers assoc with a space occupying lesion?
compress adjacent tissue
incr intracranial pressure
herniation of neural tissue
what are the cerebral peduncles?
ventral surface of midbrain
collection of UMN axons before cross-over
~corticospinal tract
uncal transtentorial herniation: defn and triad
uncus (medial temporal lobe) herniates through tentorial notch
1. "blown" pupil-dilated, fixed (CN3)
2. hemiplegia
3. coma
2 and 3 due to damaged reticular formation
what is the reticular formation?
region in midbrain
critical for consciousness
what are the areas of the lateral ventricle?
anterior horn, body, atrium, inferior horns, posterior horn
what connects each lateral ventricle with the 3rd?
foramen of monroe
what are the exit points in the fourth ventricle?
2 lateral exits: lateral foramina of luschka
1 medial exit: foramen of magendie
what makes the CSF?
choroid plexus
choroid plexus
specialized vascular structure
fusion of blood vessels and ependymal cells lining ventricles->choroid epithelial cells
how is the content of CSF regulated?
tight jxn b/w ependymal cells
tight control; highly diagnostic
how does CSF compare to blood?
low cellularity
low protein
Mg and Cl higher in CSF
K+ lower in CSF (prevent random depol)
what happens to CSF in bacterial meningitis and why? what abt diagnosing MS?
low glucose and high protein
(bacteria consume glucose)
MS- high Ig in CSF
what are cisterns?
spaces that collect CSF coming from the fourth ventricle;
in subarachnoid space
what is the breakdown of CSF? vol made and in each compartment?
choroid plexus makes 500mL a day
140mL in total ventricular system
25mL in ventricles
115mL in subarachnoid space
what is hydrocephalus? what are 3 main causes? which is most common?
"water in head"
build-up of CSF in brain
1. XS production
2.obstruction of flow (most common)
3. poor drainage
what is the name for a tumor of the choroid plexus? what would this cause?
papilloma
XS CSF prod-> hydrocephalus
what are 2 classifications of hydrocephalus?
communicating: ventricles communicate freely; flow obstructed in SA space or isnt absorbed by arachnoid villi
non-communicating: obstruction of flow b/w ventricles or b/w ventricles and SA space
what is Dandy Walker syndrome?
failure to form exit foramina off 4th ventricle
ex of non-communicating hydrocephalus: CSF cant get from 4th ventricle to SA space
causes enlargement of ventricles
what causes the BBB?
formation of tight jxns b/w endothelial cells in brain INDUCED by neighboring astrocytes
where else besides the BBB is there a barrier system in the brain?
b/w choroid plexus and CSF; formed by tight jxns b/c choroid epithelial cells
what is the name of the regions where the BBB is interrupted? ex (4)?
circumventricular organs
ex: pineal gland, neurohypophysis, median eminence, area postrema (caudal wall in 4th ventricle of medulla)
important for rel of neurohormones into blood
also, leaky under stress