Neuro Flashcards
what does the CNS comprise of?
brain & spinal cord
what is the largest & most complex part of the CNS? what 4 parts if it comprised of?
the brain! comprised of:
1. skull (cranium)
2. meninges
3. ventricular system
4. cerebral vasculature
what are the main roles of the skull & facial bones?
protect the brain from traumatic injury
what is the difference between the superior services & basilar services of the skull?
Superior services: smooth
basilar: contain ridges & folds w sharp edges
what is the role of the meninges & what three layers does it consist of?
form of another source of protection for the CNS
three layers:
1. dura
2. arachnoid
3. Pia
what are the spaces between the meningal layers called? there’s 3 of them
- epidural space (between skull bone & dura)
- subdural space (between dura & arachnoid)
- subarachnoid space (between the arachnoid & pia)
what is the dura mater? where does it get its main blood supply from?
outermost layer of the meninges that is directly beneath the skull; middle meningeal artery
what can a rupture of the middle meningeal artery result in?
epidural hematoma (space between the dura mater & skill bone –> epidural space)
what can a rupture of the intercranial & meningeal veins result in?
subdural hematoma (bleeding in the subdural space underneath the dura)
what is the arachnoid mater? what does it connect to?
2nd layer of protection in the meninges; delicate, fragile membrane that surrounds the brain (connects to the pia mater)
what is the subarchnoid space between?
arachnoid mater & pia mater in the meninges
where does CSF circulate freely?
subarchnoid space
what does rupture of an artery causing mixing of blood w the CSF cause?
subarcahnoid hemorrhage
what is the arachnoid villi? what does it absorb?
small profusions in the arachnoid mater (absorbs CSF for removal via the venous system)
what does blockage from a subarachnoid hemorrhage causse?
communicating hydrocephalus
what is the pia mater? what is its role?
final / third layer of meninges; applies large volume of arterial blood to the CNS, forms the choroid plexus within the ventricles which are responsible for the production of CSF
lateral ventricles located within the hemisphere of the cerebral cortex extend to form what?
frontal horns located in the frontal lobe
what are ventricles?
a network of cavities that are throughout the brain
which ventricles are responsible for the production & distribution of CSF?
choroid plexus
what does blockage of CSF production / distribution cause?
non-communicating hydrocephalus (build up of fluid in the brain)
what absorbs CSF?
arachnoid villi
CSF functions as a ____ & protects brain tissue from bony structures
shock absorber
what does the CSF contain?
glucose, amino acids & other nutrients needed by CNS cells
what is the CSF a poor source of?
O2 because it does not have hemoglobin or blood in it (if it does, this is BAD & not normal!)
what are the two sets of vessels that supply the brain?
internal carotid arteries & vertebral arteries
where do the internal carotid arteries supply blood to?
to the cerebrum & external supply to face & scalp
what do the two vertebral arteries form?
the basilar artery
how do the vertebral arteries help complete the circle of willis?
dives into the two posterior cerebral arteries
what is the main role of the circle of willis?
allows for collateral circulation if one vessel is occluded; permits blood to circulate from one hemisphere to the other
what should you expect to find in the CSF?
glucose
ICP is defined as….
the pressure in the cranial vault relative to atmospheric pressure
where is blood supplied from in the brain?
internal carotids & basilar arteries
what are the main roles of CSF?
production, circularization & reabsorption
what takes up the most space in the brain?
brain parenchyma (brain tissue or brain tissue volume)
what is the Monro-Kellie Doctrine?
the ability of the brain to self-regulate (increase in volume of one intracranial component must be compensated by a decrease in one or both of the other components so that the total volume remains fixed)
if the monro-Kellie doctrine does not occur, what does this cause?
increase in ICP
what is the importance of autoregulation relating to cerebral blood flow?
ability of an organ maintaining consistent blood flow to spike marked changes in BP & metabolic conditions; ensures a constant blood flow through the cerebral vessels over a range of perfusion pressures (brain’s protective device against the fluctuating changes in BP)
describe cerebral blood flow changes by both vasoconstriction & vasodilation
vasoconstriction = LESS blood flow will occur
vasodilation = MORE blood flow will occur
any activity that causes an increase in BP can also increase which two other things?
give examples
cerebral blood flow & ICP
EX: coughing, suctioning, or restlessness
what is cerebral perfusion pressure?
provides the adequacy of the cerebral circulation in delivering oxygen to the brain tissue
what is normal CBF affected by?
CPP
what is the formula for calculating CPP?
MAP - ICP = CPP
what are two things that really affect our cerebral blood flow?
- BP
- CO2
pressure auto regulation occurs when the MAP is within what range?
50 - 150 mm Hg
what does an increase in MAP indicate?
cerebral vasoconstriction (decrease in blood flow)
what does a decrease in MAP indicate?
cerebral vasodilation (increase in blood flow)
if there is an increase in CO2 & lactic acid, what does this cause in the brain?
vasodilation
if there is a decrease in CO2, what does this cause?
vasoconstriction
CO2 causes the brain to _____ which causes more ______
vasodilate; cerebral blood flow!
if there is an increase in ICP, what will happen?
CSF will be displaced into the spinal cord & the arachnoid villi will increase absorption to make more room for cerebral blood flow or the brain tissue itself
what are some things that can result from increased ICP? list 6
head injury (issue w cerebral blood flow or brain tissue volume)
bleeding in brain (issue w cerebral blood flow)
tumors (issue w brain tissue volume)
infections (issue w the CSF)
extra fluid in brain (issue w brain tissue volume)
strokes (issue w cerebral blood flow or brain tissue volume depending on type of stroke)
what are three things that affect ICP?
cerebral blood flow, CSF & brain tissue volume
what does cerebral edema affect in the brain?
brain tissue volume (water in the cells)
what can cerebral edema be caused by? list 4
brain trauma, CNS infections, brain tumors & CVA’s
what can cerebral edema lead to?
secondary complications such as hypoxia
out of the two types of cerebral edema, which one is most common?
vasogenic (often caused by brain tumors or cerebral accesses in surgery)
what can central herniation usually caused by?
cerebral edema or anything that causes an increase in ICP (bad!)
what is central herniation?
displacement of brain tissue through structures in the skull because of an increased ICP
what does central herniation lead to?
ischemic, anoxic injury because of the blood being cut off from the medulla, brain being compressed centrally therefore pushing on the brain stem
once compensatory mechanisms are exhausted, what are some signs / symptoms of central herniation? name 3
- cushing triad (imminent of death!)
- increasing or widened pulse pressure
- extreme bradycardia
- abnormal resp patterns - Bilateral pupillary dilation
- flaccid paralysis
what does cushing triad indicate pathologically?
indicates brainstem compression! (leading to decreased blood flow)
which type of patients is intracranial pressure monitoring contraindicated in?
not indicated for patients w mild to moderate brain injury (glasgow coma scale 9-15 or aware & talking)
which patients is ICP monitoring typically used in?
comatose patients or patients w severe brain injuries (usually Glasgow scale is 3-8 w an abnormal CT scan)
name 4 ICP monitoring complications
- infection (most common because of how invasive it is)
- antibiotic prophylaxis often given - obstruction (you’ll know if the drain stops draining or if their neuro status changes)
- hemorrhage (not too common)
- misplacement (if a pt pulls on it)