Exam 2 - Lecture 5 Flashcards
CSF circulatory system provides
physical cushion for structures in CNS, and environmental buffer system.
Adjectives for dura layer
Thick, leathery, robust
Dura layer extends to and terminates
where anterior and posterior root come together to form spinal root.
Epidural space
Immediately superficial to dura mater
contains adipose tissue and smaller venous vessels.
Epi means
outside
Lipophilic anesthetics into the epidural space
Adipose tissue might suck up alot of the drug and require a longer onset and will take longer for it to wear off while it seeps out of the fat.
Spinal procedure
Faster onset, needle closer to cord, in subarachnoid space. It makes it risky because if you go too far you can go into the spinal cord.
Safer area to block lower extremity
below spinal cord in the lower back
spinal nerves aren’t packed tight together, whereas spinal cord doesn’t have any movement and can damage it.
Spinal cord stretches from
tail end of brainstem (medulla) to L1
some books say L2, but father schmidt says L1 is more accurate.
Conus Medullaris
Where the spinal cord ends
What is directly underneath conus medullaris?
Spinal nerves
Cervical enlargement
C3-C6, the cord is a bit wider due to extra sensory receptors/motor neurons in upper extremities.
Lumbosacral enlargement
T11-L1, cord is wider due to lots of sensors and muscles in lower extremities.
Structures that cervical enlargement nerves feed into
Brachial plexus
Structures that lumbosacral enlargement nerves feed into
Sciatic nerve and lumbar plexus
Dura layer is continous with nerve roots down to the
Sacrum until it meets the spinal ROOT
Cauda equina
Posterior and anterior spinal roots distal to conus medullaris, safer area for procedures.
Filum Terminale Internum
Functions like ligaments, extension of pia mater, connecting the conus medullaris down to the end of the dural sac.
internum means INSIDE the dural sac.
Dural sac, what is it and where does it start and end?
AKA lumbar cistern, CSF pool at bottom of cord.
From conus medullaris to S2, allowing CSF to still circulate.
Cistern means
Pool or storage area
Filum Terminale Externum
from outside dural sac to the bottom of the coccyx
forms an anchor for the bottom of the dural sac at S2, to keep it from retracting upwards.
Growth of the bones and spine growth rate vs spinal cord
Bones tends to grow faster than the spinal cord lengthens, so there is tension in the cord. The filum Terminale keep it from retracting.
In the adult and newborns, what vertebra is the conus medullaris at?
Adult - L1
Newborn - L3
Lumbar cistern AKA?
Dural sac
CSF on the MRI is
black area surrounding cord
Is there disc between S1 and S2?
No… maybe remnants of it, at most.
Downside to dural sac
Fresh CSF is produced in brain, and new CSF has to slowly work its way down cord via cilia cells, therefore the CSF down here can get stale, and it may be old/last to get replaced. It is a very convenient space to get a CSF sample, but take the results with a grain of salt bc its older.
Good areas for CSF samples or area to give drugs
L3/L4 or L4/L5 interspace, sacral hiatus (less often used), S2 posterior Sacral foramina
Slightly off midline approach with a needle is what degree?
15 degrees
Incomplete fusion of ____ causes you to take a slightly off midline approach
Ligamentum flavum
Arachnoid trabeculae
Pillars/columns that hold up subarachnoid space for blood vessels and CSF to hangout
Epidural area in brain
up against the skull, which has its own arteries and veins to perfuse.
If you fracture the skull, what can happen?
Epidural hematoma, which is an arterial bleed.
If you bleed under the dura layer, what’s it called?
Subdural hematoma, venous bleed.
If you bleed under the arachnoid layer, what’s it called?
Subarachnoid hemorrhage, arterial bleed.
CSF pH
7.31
CSF: Bicarbonate
lower in CSF than blood concentration, making it more acidotic in nature.
CSF: Na+
Similar to blood, 140
CSF: Cl-
Higher than blood, similar to sodium, 140
CSF: K+
40% less than in blood
CSF: Mg++
Higher than in blood
What do the differences for electrolytes in CSF do for the CNS?
Keeps the brakes on the nervous system. Hyperpolarized in comparison to rest of cells.
CSF: glucose and how does it get from blood to CSF?
60 mg/dL (plasma glucose is 90mg/dL)
GLUT-1 transporters put it from blood to CSF
neurons can’t really store
glucose
Brain is very sensitive to
blood glucose fluctuations
CSF should be what color?
Clear
CSF volume is
150ml
The body makes _______mLs of CSF a day
500
CSF is replaced ______ times a day on average
3
Areas surrounding the brain get a _________ rate of CSF replacement. Dural sac gets a ____ rate.
Faster; slower
What cells produce CSF?
Ependymal cells, they separate the cardiovascular system and CSF, they have access to both.
How does a Ependymal cell work
Leaky from blood into cell to Na+, Cl- and H2O. Cell then translates that into the CSF using a Sodium pump (requires ATP), and Cl-/H2O passively follows it into the CSF. Pump runs on a fairly constant clip, and the rate can be affected by anesthetic.
Slowing down Na+ pump in the ependymal cell results in what?
Less CSF production, less Cl- and H2O following Na+.
Glucose gets into the CSF through
Blood brain barrier, not ependymal.
Does ependymal control electrolyte balance?
No, thats the astrocytes job.
Where is CSF produced?
Containers called Choroid plexus: (2) lateral ventricles, 3rd and 4th ventricles.
3rd ventricle is near
the diencephalon, where the hypothalamus is.
4th ventricle is near
the cerebellum, inferior/anterior side of it.
Lateral ventricles are buried deep in
Cerebral hemispheres
Lateral ventricles drain into the
3rd ventricle, which drains into the 4th ventricle.
All 4 ventricles have a
Choroid plexus
Pathway for Lateral ventricles to dump into 3rd ventricle
Interventricular foramen aka Foramen of monroe
Pathway for 3rd ventricle to dump into 4th ventricle
Cerebral aqueduct, aka aqueduct of sylvius
Once in 4th ventricle, it can exit through 4 paths
- Central canal
- (2) lateral apertures aka foramen of luschka.
- Median aperture AKA foramen of magemdie– provides CSF to circulate around cerebellum. called median cause its comes out midline posteriorly.
If you occlude one of the foramens of the ventricles, they will ___
Grow in size and pressure the glial cells/neurons/brain structures. Causes Hydrocephalus.
Most common foramen occlusion in ventricles
Cerebral aqueduct of sylvius. Tumor or something lodged in there, will be very difficult to fix.
Non-communicating hydrocephalus
block in one of the foramens of ventricles.
Communicating hydrocephalus
CSF isn’t being absorbed or removed at normal clip like it normally is, no blockages.
Places for CSF to reabsorb to cardiovascular system
Arachnoid granulations at top of brain, midline. right with longitudinal fissure. They are pressure blow off valves.
Normal ICP
10
If ICP is 12?
Blow off valves (arachnoid granulation) will open and dump CSF into cardiovascular system.M
A small amount of CSF can be reabsorbed in
areas surrounding the cord.
CSF is being reabsorbed into the cardiovascular system at the __________ its being produced.
Same rate
If you have a stroke and have blood clots at arachnoid granulations, it will
cause CSF to not drain, and cause communicating hydrocephalus.
Cerebellum is responsible for
Coordinating complex tasks.
e.g. walking down the street, requires complicated motor function by neurons in cerebellum.
Median aperture drains into
Cerebellomedullary cistern aka cisterna magna
Pool of CSF fed from median aperture, circulated around cerebellum, keeps it fresh and new.
Is it possible to sample CSF through cisterna magna?
Yes, but highly invasive. Through foramen magnum.
Cranial sinuses mean
Venous collecting system
Superior sagittal sinus
Large medial venous collecting area
Inferior sagittal sinus
runs same plane as super sagittal, just below it, still midline.
Falx cerebri
connective tissue connecting left and right hemisphere.
Where does the occipital lobe sit on?
connective tissue called Tentorium cerebelli, acts like like a shelf for occipital lobe.
What is below tentorium cerebelli?
Cerebellum
Straight sinus
Last stretch of inferior sagittal sinus before it reaches sinus confluence .
Sinus confluence
Where superior/inferior sagittal sinuses connect via straight sinus and transverse sinuses collect on the anterior posterior part of skull.
Transverse sinus
Where blood go laterally to exit.
Sigmoid sinus
Hairpin turn before blood drains into jugular vein.
Cavernous sinus
Venous collection pool located in front middle part of brain, usually blood from face/front of brain, feeds into sigmoid sinus.
Jugular foramen
Where sigmoid sinus dumps blood to exit the brain
External jugular
Superficial venous vessels.
Internal jugular vein
Blood comes from sigmoid sinus
How many arteries feed into brain?
4
_____ vertebral arteries run up ________
2; back of beck to supply back of brain
_____ carotid arteries
2
External carotid artery
Superficial anterior structure of brain
arterial brain blood flow is
750ml per minute, or 15% of cardiac output.
Total cardiac output is
5L per minute.
Brain makes up ________ of our body weight.
2-3%. results in lopsided blood flow per quantity of tissue.
Brain blood flow total ratio per tissue
50ml/min per 100grams of tissue.
what percent of blood flow to brain is for grey and white matter?
80:20 grey to white
