Lecture 2-spinal cord Flashcards
what are the boundaries of the spinal cord?
top/rostral/superior:
- foramen magnum
- 1mm caudal to the pyramidal decussation
bottom/caudal/inf
-btwn L1 and L2 vertebrae
site of conus medullaris
what do the cervical enlargements innervate?
what about the lumbar enlargement?
upper extremities
lower extremities
which space is CSF in
subarachnoid space
what are the differences btwn cranial and spinal meninges?
- dura in the cord has only 1 layer. in the brain there are 2
- outer dural layer that is present i nthe brain end at the foramen magnum, so the cord only covered by an inner investing dural layer - epidural space is not a potential space in cord but an actual space filled w/ fat and veins
what do the meninges of the brain and cord have in common
shared subarachnoid space bc CSF is able to bathe the cord and spinal nerve roots
CSF heads caudally to the
lumbar cistern
how is the spinal cord pairs divided up
8 cervical 12 thoracic 5 lumbar 5 scaral 1 coccygeal
what does each spinal nerve innervate?
what does each spinal cord segment innervate?
a single dermatome and myotome
a dermatome and a myotome
what does the cervical enlargemnt innervate
upper extremities from C5 to T1
what does the lumbosacral enlargement innervate
lower extremities from L2 to S3
where does the spinal cord end
btwn L1 and L2 vertebrae
what is a papilledema
the bilateral sweling of both optic discs due to increased intracranial pressure
- if the pt develops a space occupying lesion (tumor or bleeding) there’s not enough room in skull so the ICP increases and can be transmistted along both optic nerves due to the SHARED SUBARACHNOID SPACE.
- same CSF that circulates around the brain and cord so its also around the optic nerces
what are the two investigations needed for possible causes of elevated ICP
- neuroimaging (MRI/MRV) to look for structural lesions
- if imaging is normal, next is CSF analysis by lumbar puncture
if LP proves that the ICP is high, then the bilarteral disc edema can be specifically called a papilledema
where is CSF sampled from in a LP
lumbar cistern
what does a LP allow documentation of?
the CSF sample is sent to a lab to analyze its…?
- opening pressure
2. composition
where is the lumbar cistern located
just below the spinal cord itself but still within the dural sac (from L1-L2 vert to S2 vert)
where is the needed in an LP for adults placed?
L3-L4 or L4-L5
what is the preferred pt position when doing an LP?
lateral decubitus
- lying on side
- in fetal position
what is the cut-off of the normal range of the opening pressure?
> 250 mmH2O
where does the dural sac end
S2 (therefore thats where the lumbar cistern ends also)
where is the conus medullaris
what is it
just below L1
caudal termination of the cord
where is the cauda eqina
spinal nerve roots from the lumbosacral region extending beyond the conus medullaris
what is the filum terminale
a thickening of the meninges which anchors the spinal cord around the coccyx
are spinal nerves CNS?
no, they are PNS
what are spinal nerves covered by
spinal roots?
epineurium
meningies
what are dorsal roots
afferent sensory fibers entering the cord.
what type of neurons are dorsal root ganglion
pseudo-unipolar neurons w/ both central and peripheral processes
what are ventral roots
where are their cell bodies or origin
- efferent motor fibers going out to the periphery. probaby to innervate somatic or autonomic muscles
- inside the spinal cord’s gray matter
each spinal nerve if formed by the union of what?
what kind of fibers do they contain?
dorsal and ventral root
sensory and motor fibers (mixed nerve(
what are the roots and rootlets enclosed in ?
what is the spinal nerve ?
- dural sleeve
2. epineurium
waht do the spinal nerve branch off into? what kind of fibers do they contain?
dorsal and ventral rami
motor and sensory fibers, mixed
ventral/anterior rami become what because they are so big? between what do they not form those? and why?
plexi
T2 and T12
sympathetics
what does the smaller dorsal primary ramus innervate?
-skin of back,
-deep back muscles,
- joints btwn vertebrae
both sensory and motor
what do the ventral rami supply?
skin of trunk and limbs
muscles of trunk and limbs
Primary rami are….
spinal nerves are……
dorsal roots are….
ventral roots are….
mixed
mixed
sensory
motor
white rami communicans are only present where….
gray rami?
why?
- T1-L3 bc sympathetic preganglionics are only present thoracolumbar
- present at all levelts bc all levls of the body get post gagnlionic sympathetic fibers
how many pairs of cranial nerves are there? where do they exit from?
how many pairs of spinal nerves are there? where do they exit from/
12 pairs, exit through skull foramina
31 pairs, exit through intervertebral foramina
do peripheral nerves contain sensory or motor info?
it depends-bc spinal nerves are mixed but cranial nerves can be mixed, sensory, or motor.
what are the targets of the ANS
how do they innervate their targets
cardiac muscle, smooth muscle, and glands
through a 2 neuron chain
what are the two neurons in the 2 neuron chain
1: pre-ganglionic neuron, originiates inside the CNS , which means the cell bodies of origin are from the brain or spinal cord
2: postganglionic neuron, originates in the ganglion which means cell bodies of origin are in the PNS
if the preganglionic cell body is craniosacral (in brainstem or sacral spinal cord), it is…
if the preganglonic cell body is thoracolumbar (located in the thoracic or lumbar spinal cord) it is..
parasympathetic , its axons will exit the brainstem as cranial nerves or ventral roots and then spinal nerves
sympathetic, its axons exit via ventral roots
what does cranio mean?
what does sacral mean?
preganglionic cell bodies are located in cranial nerve nuclei in the brainstem CN nuclei 3, 7, 9, 10
preganglionic cell bodies are located in the sacral region of the spinal cord and are S2 to S4
what does it mean to say “thoracolumbar”
sympathetic pre ganglionic cell bodies that are located in teh T1-L3 spinal cord segments
in the lateral horn gray segments of T1-L3
lateral horns contain ….
ANS motor info, specifically sympathetic preganglionic efferents
which cranial nerves are parasympathetic in function? sympathetic?
3, 7, 9, 10
NONE
what are the two types of sympathetic chain ganglia
- sympathetic chain ganglia (aka paravertebral ganglia)
2. prevertebral ganglia
what neurotransmitter is used in preganglionic neurons?
what does the parasympathetic postganglionic neuron use?
what does the sympathetc postganglionic neuron use?
acetylcholine
acetylcholine
norepinephrine
where are the sympathetic preganglionic cell bodies
CNS
thoracolumbar cord at T1-L3
later horns (gray matter)
what are the sympathetic preganglionics first couple steps
- pregagnlionic axons exit the cord ventrally as ventral roots
- enter the spinal nerve
- go through the ventral primary ramus
- travel through the white ramus communicans
what are the 3 steps that the sympathetic preganglionics can take
- synapse there in the sympathetic chain of ganglia
- go another area of the chain (up or down) before synapsing
- leave to synapse in a prevertebral ganglion
what kind of fibers do gray rami communicans have? what about white rami communicans?
post-ganglionics (unmyelinated)
pre-ganglionics (thinly myelinated)
where are white rami communicans found?
where are gray rami communicans found
T1-L3 (thoracolumbar)
all spinal cord levels
what do white rami communicans contain?
what do gray rami communicans contain?
myelinated preganglionic sympathetic fibers
unmyelinated postganglionic sympathetic fibers
where does the oculosympathetic pathway begin? what does it begin w/?
in the hypothalamus w/ the “central neuron”
what do the first-order fibers do after they leave the hypothalamus
descend through the lateral brainstem (midbrain, pons, medulla) and cervical spinal cord
when the first order neurons reach the ciliospinal center of budge at spinal cord segments _________, the central neuron synapses onto the preganglionic cell bodies located in the _____
C8, T1, and T2 lateral horn (intermediolateral cell column)
where do the preganglionic neuron (2nd order neuron) eventually terminate/synapse in?
superior cervical ganglion
what are the 2 routes for postganglionic oculosympathetics
- hitching a ride w/ nasociliary nerve (V1) in orbit
2. through ciliary ganglion w/o synapse (unlike parasym to sphincter)
second preganglionic neurons exit ventral spinal roots and arch over apex of lung to ascend in ___________, synapsing in _______ and exiting as third-order neuron
cervical sympathetic chain
superior cervical ganglion
third order postganglionic neuron travels w/ _____ artery into ______ w/ ophthalmic branch of of CN5 joining nasociliary branch of CN5 or passes through the ______directly, reaching the eye as ______ and _____ ciliary nerves
carotid
cavernus sinus
ciliary ganglion
short and long
what do preganglionic parasympathetic fibers arise from
whta do they exit as
what do they synapse at
what do they reach the eye as
accessory oculomotor nucleus
oculomotor nerve
ciliary ganglion
short ciliary nerves
what kind of tumor causes horners syndrome
apical lung tumor (pancoast tumor) bc preganglionic fibers pass by the lung apex (which is near the lower part of the brachial plexus)
parastympathetic brainstem nuclei CN3= ? CN7 =? CN9= ? CN10=?
edinger-westphal
superior salivatory nucleus
inferior salivatory nucleus
dorsal motor nucleus of X
