6901 Neuro Part I Flashcards
Which structure has more space to expand, the brain or sc?
sc
How do unmyelinated versus myelinated nerves travel?
unmyelinated= AP; myelinated= saltatory
What do dendrites and axons do?
dendrites carry impulses to cell body and axons carry nerve impulses away from cell body
What part of neuron is unmyelinated/gray?
cell body and some axons
This provides support for neurons and has nutritive and metabolic functions. Has feet that project from cell and sometimes terminate on blood vessels and not other neurons? May play role in BBB?
astrocytes
Type of brain cell that has role in CSF production?
ependymal cell
Type of brain cell which participates in phagocytosis with CNS?
microglia
Type of brain cell which provides insulation, by forming the myelin sheath around the brain and sc?
oligodendrites
This type of cell provides insulation as forms myelin sheath in peripheral nerves?
Schwann cell
How do neurons communicate with each other?
by means of NTs across synpases
Inhibitory and excitatory NT?
major inhibitory is GABA; major excitatory is glutamate
How does a GABA NT work?
(hyperpolarizing); it opens neuronal membrane Cl channels and produces hyperpolarization
How does a glutamate NT work?
activation depolarizes neurons which makes it more likely that they will fire APs
Where is GABA concentrated?
cerebral cortex, cerebellum, basal ganglia, spinal cord
This NT is important in antagonizing the excitatory effects of amino acid NTs?
GABA
This NT plays a large role in learning and memory and perhaps interactive and memory formation in awareness under anesthesia and the appreciation of pain?
glutamate
Where is glutamate concentrated?
cerebral cortex, hippocampus, substantial gelatinosa of the sc
This NT is released in excitatoxic neuronal injury after TBI or ischemic injury?
glutatmate
How is glutamate formed?
deamination of glutamine supplied by Kreb’s cycle
What are 3 categories of NTs?
monoamines (epi, dopa), amino acids (GABA, glutamate), neuropeptides (substance P, pituitary and endocrine hormones)
How does glutamate work?
activates NMDA (ligand gated inotropic receptor) that cause conformational change in receptor and opens Na channel which results in depol of post synpatic membrane
Neurons are classified according to and what are 3?
specific function; sensory, motor, interneuron
Afferent part of neuron goes in what direction and is what type of neuron?
goes towards posterior root, is sensory
Efferent part of neuron goes in what direction and is what type of neuron?
away from anterior root and is motor
What do interneurons do?
connect adjacent neurons
How much intracellular transport takes place in CNS and why?
very little bc lack transport mechanisms
What type of cells form tight junctions between adjacent cells to prevent transport of polar substances from intravascular to extravascular cerebral dept?
endothelial
What separates the 2 cerebral hemispheres?
longitudinal fissure
Describe the gyri?
is elevated and outer 3 mm area which is convoluted and increases the surface area
What do the sulci do?
grooves which separate the gyri
4 lobes of the brain?
frontal, parietal, temporal, occipital
Lobe of brain which is responsible for motor and thought?
frontal
Lobe of brain which is responsible for sense of pain, pressure, temp, and touch?
parietal
Lobe of brain which is responsible for hearing and smelling, recognition, and memory?
temporal
Lobe of brain whose function is vision?
occipital
Brainstem consists of?
midbrain, pons, and medulla
Part of brainstem that maintains consciousness, arousal, and alertness?
RAS
What does pons connect?
midbrain and medulla oblongata
This part of brain contains the respiratory and CV centers?
medulla
How many meningeal layers and spaces are there that cover the brain and spinal cord?
3 and 3
Meningeal layers going from outside to inside?
dura, arachnoid, pia
Meningeal spaces going from outside to inside?
epidural, subdural, subarachnoid
This meningeal layer is thin and avascular and serves as a major pharmacologic barrier?
arachnoid
This meningeal layer is thin, soft, highly vascular, and provides nourishment to spinal cord and brain
pia mater
This meningeal layer is thick and provides structural support to spinal cord?
dura mater
This meningeal layer forms a good portion of the BBB?
arachnoid
What is the space called above the dura mater?
epidural space
What is the space called between the arachnoid and pia?
subarachnoid space
What is the space called between the dura and arachnoid?
subdural
Which space contains the CSF?
subarachnoid
Pneumonic for memorizing CN names?
On Old Olympus Towering Top A Fin A(V)nd German Viewed S(A)ome Hops
Sensory/motor/both CN pneumonic?
Some Say Money Matters, But My Brother Says Big Brains Matter More
Angostroms between tight junctions in BBB and then in rest of body?
8; 65
Movement across BBB is governed by what 4 things?
size, charge, solubility, degree of protein binding
4 substances that struggle to pass thru BBB?
large molecules, high electrical charge, low fat soluble, polar molecules
Water, lipid soluble molecules such as (3) can pass thru BBB?
O2, CO2, anesthetics
Some problems which can cause a disruption in BBB?
HTN, TBI, subarachnoid or cerebral hemorrhage, ishcemia, mass or lesions
2 main arteries which supply blood to brain? Which supplies the anterior portion and which supplies the posterior portion?
internal carotid arteries and vertebral arteries; anterior: internal carotid; posterior: vertebral
Where does carotid bifurcate in to internal and external carotid arteries?
level of 3rd cervical vertebrae
CN whose motor control is of the face and salivation. Sensory is taste and cutaneous sensations
facial
CN which has motor control of some eye muscles and eyelid?
oculomotor
CN which has motor control of some eye muscles?
trochlear or abducent
CN which is responsible for chewing muscles and facial sensation?
trigeminal
CN which is responsible for motor impulses to pharynx and shoulder?
accessory
CN which is responsible for salivation, sensation of skin, taste, and viscera?
glossopharyngeal
CN which has motor control of tongue, some skeletal muscles, some viscera, and sensation from skin and viscera?
hypoglossal
8 ways in which CBF can be manipulated?
CMRO2, PaO2, PaCO2, autoregulation, temp, viscosity, ANS, anesthetics/meds
Normal rate of CBF?
50mL/100g/min of brain tissue
What percentage of CO is CBF?
15-20
As CBF changes so does?
CBV
Why does brain get disproportionately high part of CO?
high metabolic rate and inability to store energy
CMR is directly r/t?
of neurons and rate of depol
Gray matter gets what % of CBF and why?
80%, higher metabolic rate
How many mL/min is CBF?
700-750 mL/min
Too little CBF leads to? And too much CBF leads to?
ischemia; edema, bleeding
CPP=?
MAP- ICP or CVP (whichever is higher)
Where do you measure CVP?
at ear canal/meatus
Normal ICP?
Pressure that drives blood flow to the brain?
CPP
CPP is primarily dependent on? What’s the exception?
MAP; increased ICP
When ICP> 30, what is compromised even with a normal MAP?
CBF CPP
A CPP of what can show flat EEG and result in irreversible brain damage?
25-40
Brain uses what % of total body O2 consumption?
20
CBF is tightly coupled to?
metabolism
High O2 consumption of brain is roughly what mL/min in adult?
50 mL/min
Neuronal activity in brain accounts for what % of energy use?
60
Most cerebral O2 consumption is used to?
generate ATP to support neuronal electrical activity
Increased ATP/energy leads to increased CMRO2 and therefore?
increased blood flow
What determines blood flow in the brain?
regional metabolism rate of O2
Primary fuel for brain is what and at what rate?
glucose; 5 mg/100g/min
How is ATP generated? And >90% of that is what type of process?
glycolysis; aerobic
CMRO2 parallels?
glucose consumption
Since the brain has no O2 stores, ATP stores are depleted and cellular injury can occur how soon?
3-8 minutes
What does mild hyperthermia do to the CMR and CBF?
increases and increases
CBF is directly influenced by ____= glucose consumption?
CMRO2
What is autoregulation?
ability of cerebral vasculature to maintain relatively constant blood flow despite large changes in BP
CBF maintains constant with CPP (MAP) between?
50-150
MAP for lower limit of autoregulation is?
> 70
MAP> what disrupts the BBB and leads to edema and bleeding?
150-160
What does cerebral autoregulation curve do with chronic HTN?
shifts to the right
MAP
50
What does PaCO2 do to CBF and vasculature?
dilation and increases blood flow
Beyond autoregulation limits CBF is dependent on?
perfusion pressure
What can alter brain autoregulation?
brain injury or intracranial surgery
PaO2 has little effect on CBF until it falls below?
50
Most important regulator of CBF?
PaCO2
Hypocapnia does what to the vasculature?
constricts
CBF increases or decreases what % for each 1 mm change in PaCO2?
3
Do blood vessels in ischemic areas react the normally to changes in CO2?
no
One way to get a steal phenomenon w PaCO2?
hypoventilation with hypercarbia (increased CBF to normal areas)
One easy way to relax the brain to change the ICP?
hyperventilation
How long can hyperventilation relax the brain? And how quickly?
acutely (
PaCO2
30
What happens to CBF when PaO2
increases
ICP > 30 does what to CBF?
decreases
CPP
decreases
CPP > 150 does what to CBF?
increases
A decreased temp does what to neuronal metabolism and CBF?
decrease, decrease
CBF decreases what percent for every 1 degree Celsius decrease in temp?
5-7%
Hyperthermia does what to CBF and CMR?
increases, increases
Hypothermia is used for what and what do you have to monitor for?
high risk intraop ischemia; dysrthymias and coagulation dysfunction
Most important factor in viscosity?
hct
What does increased viscosity (increased hct) do to CBF?
decrease
What does decreased viscosity (decreased hct) do to CBF?
increase
Suggested optimal hct adequate for O2 delivery is?
30%
Intracranial vessels are innervated by?
SNS, PNS
What type of innervation may lead to passing out?
SNS
What does SNS innervation do to the vasculature and CBF?
constriction; decrease in CBF
What does PNS innervation do to the vasculature and CBF?
dilate; increases CBF
3 places where CSF is located?
subarachnoid space, cerebral ventricles, cisterns
Function of CSF?
bathes and cushions brain and spinal cord
Where is CSF produced and secreted?
produced by choroid plexus in the ventricles; secreted by ependymal cells of choroid plexus
CSF is produced at a rate of what? And the total volume at one time is? And how much is produced daily?
30 mL/h; 150 mL; 450-500 mL
How often does CSF volume replace itself?
3-4 hours
Normal CSF pressure is between?
5-15
% of brain, blood, and CSF in cranial vault?
80% brain, 12% blood, 8% CSF
Brain matter is composed of?
neurons, glia, interstitial fluid
Blood/fluid part of brain consists of?
blood, vascular space, ICF, ECF
Where is CSF reabsorbed?
arachnoid villi
Where does brain stem turn in to spinal cord and exit CNS in to spinal cord?
foramen magnum
Cerebral bolt or ventriculostomy in supine position pressure should be?
10-15 torr
ICP refers to?
supratentorial CSF pressure
An ICP of what is considered intracranial HTN?
15
Normal ICP?
5-15
4 compensatory mechanisms used when ICP is increased?
decrease CSF production, increase CSF absorption, displacement of CSF from cranial to spinal compartment, decrease in CBF (venous)
As the cranial volume increases, CSF is translocated in to?
spinal canal
Ischemia leads to?
cerebral edema and further increases in ICP
Symptoms of increased intracranial HTN?
HA (that wakes them up at night), N/V, blurred vision, somnolence and neuro deficits, papilledema, seizures/coma, Cushing reflex
3 s/s Cushing’s triad?
HTN, bradycardia, respiratory irregularities
Some causes of intracranial primary HTN?
brain tumor, trauma, nontraumatic intracerebral hemorrhage, ischemic stroke, hydrocephalus, idiopathic or benign intracranial HTN, abscess, infection, cyst
Causes of extracranial/secondary HTN?
hypercarbia >35, hypoxia
Post op causes of intracranial HTN?
mass lesion (hematoma), edema, disturbances in CSF, increased CBV
What does edema look like on a CT scan?
region of hypodensity
What does increased airway or intrathoracic pressure do to venous pressure?
increased jugular venous pressure
6 things which increase CBV?
increased PaCO2, decreased PaO2, increased JV pressure, some anesthetics, vasodilators, seizures
Intracranial vault concentration is lost when ICP >?
30
Brain response to ischemia is?
edema
Increase in ICP and ischemia cause what reflex?
Cushing’s
Normally cerebral ischemia leads to Cushing’s reflex which will increase?
MAP
Cushing’s reflex only compensates to a certain point and then what falls leading to further ischemia?
CPP
Why does a reduction in SBP aggravate ischemia?
causes reduction in CPP
2 compensatory mechanisms for high ICP?
translocation of CSF to spinal CSF space and venous blood to the extracranial veins
2 meds that increase ICF or ECF?
diuretics or steroids
Increases in blood volume are usually associated with increases in CBF. Exception is?
ischemia from hypotension or vessel occlusion at which time CBV may increase as cerebral vasculature dilates in response to reduction in CBF
3 things we can manipulate in CNS?
CSF: drain; blood volume: diuretics, steroids, positioning; cells (surgical removal glia, tumors, extravasated blood)
Gold standard for ICP monitoring?
intraventricular catheter
4 types of drains?
subdural bolt, ventriculostomy, epidural transducer, subdural fiberoptic catheter placement
Level drain w?
right atrium or angle of monroe
How do steroids help with CSF/fluid volume reduction?
decrease edema
4 diuretics to give to decrease CSF/fluid?
Lasix, hypertonic saline, Mannitol, Diamox
One way to decrease CBF?
decrease CBV
Decreased CBV and CBF does what to ICP?
decreases
Anesthesia can provide rapid alteration in which area of the intracranial vault?
CBV reduction/CBF reduction
3 things which increase CMR?
arousal, pain, seizures
Arterial blood volume can be reduced by?
preventing increase in CMR, barbs, optimizing hemodynamics
In hypothermia CBF (CMRO2) is decreased what % for every 1 degree C decrease in body temp below 37?
7%
Keep hct in what range to maximize O2 transport?
30-35%
Below what temperature can you not improve intracranial HTN?
35
Some ways to increase venous outflow and drainage?
elevate head, avoid constriction of the neck, avoid PEEP and excess airway pressures
