Lecture 1: Spinal Cord Flashcards
describe the path of the spinal cord (where it starts, ends, and where there are enlargements)
starts at foramen magnum
cervical enlargement for cervical and brachial plexuses
lumbosacral enlargement for lumbar and sacral plexuses
ends at T12~L2 vertebral level
what spinal nerves are considered part of the lumbar section of the spinal cord
T11-L5
what spinal nerve exits from below C7 vertebrae
C8 nerve
vertebral foramen houses
spinal cord
where do spinal nerves exit
intervertebral foramen
what makes up the spinal canal
vertebral foramen and sacral canal
what layer of the meninges is filum terminale externum derived from
dura mater
what ligaments are derived from a condensing of the pia mater
denticulate ligament (teeth like)
filum terminale internum
blood supply to the spinal cord
anterior spinal artery supplies most of the spinal cord and anterior medulla
posterior spinal arteries (x2) supplies most of the posterior spinal cord and medulla
both receive segmental support as well
where does the anterior spinal artery stem from
both vertebral arteries give a branch to form
where do the posterior spinal arteries derive from
each of the PICA gives off one posterior spinal artery
white matter is made up of
myelinated axons
gray matter is made up of
unmyelinated axons
ventral vs dorsal horn functions
ventral = motor
dorsal = sensory
compare the proximal vs distal spinal cord in terms of gray matter and white matter as well as the corresponding function
proximal = more ascending/descending tracts so more white matter than gray matter
distal = less descending and ascending tracts and more gray matter than white matter
where in a cross section of the SC can you see faciculus cuneatus
above T6
where in a cross section of the SC can you see fasciculus gracilis
below T6
describe gray matter
nuclei inside SC
10 laminae from dorsal to ventral with different functions
where is lamina IX
in both lamina VII and VIII
substantia gelatinosa: levels of SC, lamina, and function
all levels
lamina II
function = modulate pain and temp info transmission
Clarke’s nucleus: levels of SC, lamina, and function
levels: T1-L2
lamina VII
function: posterior spinocerebellar tract cells
intermediolateral column: levels of SC, lamina, and function
levels: T1-L2
lamina: VII
function: preganglionic sympathetic neirons
sacral parasympathetic nucleus: levels of SC, lamina, and function
levels: S2-S4
lamina: VII
function = preganglionic sympathetic neurons; pelvic floor function
accessory nucleus: levels of SC, lamina, and function
levels: C1-C5
lamina: IX
function: motor neurons to SCM/trapezius
phrenic nucleus: levels of SC, lamina, and function
levels = C3-C5
lamina: IX
function: motor neurons for diaphragm
what is the corresponding lamina for the somatic motor efferent portion of the spinal cord
lamina IX in lamina VIII
what are the corresponding lamina for the somatic sensory afferent portion of the spinal cord (except for C1)
Lamina I-V
what are the specific spinal levels for visceral motor/efferent signals and what lamina is related
sympathetic = T1-L2
parasympathetic = S2-S4
lamina IX in lamina VII for both
what are the specific spinal levels for visceral sensory/afferent and the corresponding lamina
follows same path as visceral motor
sympathetic = T1-L2
parasympathetic = S2-S4
Lamina I-V
most spinal levels involved in the sympathetic trunk
what is contained in the ventral horn of the spinal cord
LMNs that directly innervate muscles
what is the distribution of the LMNs in the ventral horn from medial to lateral and anterior to posterior
medial to lateral = axial to distal extremity
anterior to posterior = extensors to flexors
correlates to the 3 functional lobes of the cerebellum
describe a lower motor neuron
executors of movements
multipolar neurons with dendritic trees (highly regulated function)
somata are clustered in a column to regulate one muscle (called a motor neuron pool/nuclei)
cranial to caudal vs proximal to distal
describe the dorsal column medial lemniscus system
axons of 1st order neurons in dorsal root ganglion
axons are large and myelinated
no decussation in SC
maintains somatotopy of sacral to cervical from medial to lateral respectively (fasciculus gracilis to fasciculus cuneatus)
function: conscious proprioception/vibration/fine touch
describe the pathway of the anterolateral system (aka the spinothalamic pathway)
non-myelinated axons from 1st order neurons in dorsal root ganglion
axons synapse with 2nd order neurons in dorsal laminae
decussate at the anterior white commissure to the contralateral anterolateral funiculus
describe the function of the anterolateral system
anterior spinothalamic pathway: diffuse pain, no somatotopy maintained, bilateral projection
lateral spinothalamic pathway: sharp pain, temp, crude touch, itch (if somatotopy is maintained, it is for conscious proprioception)
what ascending pathways are a part of the lateral funiculus
From the anterolateral system:
-lateral spinothalamic tract for crude touch, pain, temp, itch, and sharp pain
from the spinocerebellar tracts:
- posterior spinocerebellar tract for unconscious proprioception
-anterior spinocerebellar tract for motor information
where does the posterior spinocerebellar tract travel
to clarkes nucleus and then ipsilateral ascending to cerebellum
where does the anterior spinocerebellar tract decussate
decussates after clarkes nucleus at anterior white commissure
describe the somatotopy of the DCML
from medial to lateral = lower to upper limb/back
posterior to anterior: different sensory modalities, proprioception to fine touch
describe the somatotopy of the lateral spinothalamic tract
superficial to deep: lower to upper limb/back
anterior to posterior: different sensory modalities
what ascending tracts do not cross in the spinal cord
fasciculus gracilis
fasciculus cuneatus
lissauer’s tract
posterior spinocerebellar tract
what ascending tracts cross in the spinal cord
anterior/lateral spinothalamic tract
anterior spinocerebellar tract
spinoreticular tract
what does the lateral funiculus control
flexor muslces
innervates posterior ventral horn
fine motor control
where is the decussations of the corticospinal tract
70-90% of fibers decussate at the pyramid (part of the lateral corticospinal tract)
10-30% of fibers descend ipsilaterally (part of ipsilateral lateral and medial corticospinal tract)
no somatotopy below the pons
what is the rubrospinal tract responsible for
not very prominent in human beings
role in fine motor control
path of rubrospinal tract
synapses at red nucleus
decussates in midbrain
what does the anterior funiculus control
mainly extensors
innervates medial and anterior ventral horn
what pathways are a part of the anterior funiculus and their subgroups
medial corticospinal tract
vestibulospinal tract - medial and lateral portions
reticulospinal tract - pontine and medullary portions
what descending tracts are already crossed when in the spinal cord
lateral corticospinal tract (at medullary pyramid)
rubrospinal tract (at midbrain)
what descending tracts of the spinal cord are uncrossed
vetibulospinal tract
reticulospinal tract
anterior/medial corticospinal tract
most project bilaterally
what information can be learned from knowing which descending tracts of the spinal cord are crossed or uncrossed
the trunk and even proximal extremities always remain functional immediately after brain injuries
fine motor control patterns are difficult to recover
what are propriospinal neurons
somata and axons only in spinal cord (>90% of spinal neurons)
somata surrounding or in different rexed laminae (mainly III) of spinal cord
fasciculus proprius: interconnects different spinal cord levels (like association fibers of cerebrum)
what are central pattern generators
like apps of smartphone
automatic prewritten motor programs
what are interneuron coordinate reflexes
like different types of apps
automatic prewritten motor programs
what are the functional components of the propriospinal neurons and tracts
central pattern generators
interneurons coordinate reflexes
interneurons for visceral pain sensory ascending tracts (archispinothalamic tract)
interneurons for higher level descending tracts
what is brown sequard syndrome
R or L hemi spinal injury
ipsilateral deficits due to tracts w/o decussation:
- motor functional loss
- proprioception/vibration/fine touch loss
-unconsious proprioception
contralateral deficits due to decussations that occur at anterior white commisure
- pain/temp/crude touch
-motor info
what is a syrinx
cyst in syringomyelia (spinal cord) or syringobulbia (brainstem)
compression of anterior white commissure = bilateral anterolateral system impaired resulting in pain/paraesthesia in same dermatome bilaterally
above C2 level results in head and scalp symptoms due to the spinal trigeminal nucleus descending to c2 level as well
