spinal cord function adn dysfunction Flashcards
summarise the spinal cord segments
31 spinal segments
31 pairs of nerves - 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal - leave the vertebral column through intervertebral foramen
why are there cervical and lumber enlargements *
for innervation of the limbs
there are many more neurons in the cord at these points
what does the cervical enlargement innervate and what spinal segments are involved *
upper limbs
C3-T1
what does the lumbar enlargement innervate and what spinal segments are involved *
upper limbs
L1-S3
describe at what level the nerves leave the vertebral column *
C1-C7 nerve leave above the relevant vertebrae,
C8 leaves between C7 and T1 vertebrae, every nerve after that leaves after the relevant vertebrae
describe the discrepancy between the spinal levels and the vertebral levels *
each has the same number as segments - spinal cord segment is shorter
therefore coccygeal segment of spinal cord is at the 2nd lumber vertebrae
where the nerve emerges from the cord is different from where it emerges from the vertebrae - the nerves get more angled lower down
what is the clinical relevance of the discrepancy between the spinal and vertebral levels *
the effect of an injury depends on the spinal level and the vertebral level that it occurs
describe the meningeal coverings *
dura mater - continuous with inner sheet of dura in cranium, forms dural sac, extends to S2, hard
arachnoid mater - ballooned up against dura, spider like
pia mater - adheres tightly to the surface of the spinal cord - the filum terminale is an extension of the pia mater - tethering the spinal cord to the sacrum
describe the epidural space *
true space - between dura and periosteum, filled with fat and venous plexus
describe the subarachnoid space *
filled with CSF
continuous with subarachnoid space of cranium
describe the posterior root *
carries sensory info
cell bodies in spinal ganglion
enters the spinal cord in the posterolateral sulcus
describe the spinal ganglion *
contains the nerve cell bodies or primary sensory afferents, pseudounipolar neurons - there are no synapses
describe the anterior root *
carries motor info, exits spinal cord through anterolateral sulcus
describe the denticulate ligament
extensions of pia - anchor the spinal cord to the dura
lateral denticulate ligaments separate posterior and anterior roots
comparison between the meninges in the brain and in the vertebral column *
no space between the dura and the skull, but tehre is space between the dura and the vertebral column - useful to inject anaesthetics into the epidural space in the spine instead of using a general anaesthetic - eg in C section
also because the spinal cord ends at L2 - unlikely to be damaged
also can take a lumbar puncture of subarchnoid space- sample the CSF that flows down the spinal canal - can see what is happening in brain and if there is a sign of infection and add anaesthetics here
also can add spinal blocks into subarachnoid space - when you know the dose you will need
where are the ascending and descending tracts in the spinal cord *
in the white matter
define dermatome
area of skin supplied by one single spinal nerve or spinal segment
define myotome
collection of muscles innervated by single spinal nerve or segment
what are rootlets
they come from the horns of grey matter and join to form roots
define roots *
roots only have either sensory or motor fibres
they mix with the other type of root (motor/sensory) to form the spinal nerve
a bundle of nerve fibres at its emergence from the spinal cord
what is the spinal nerve *
mix of nerves - going into dorsal horn and out of ventral horn
what is a rami *
have anterior and posterior rami mix of sensory and motor branches of the spinal nerve anterior innervates most of body posterior smaller, innervate skin and muscles of back
illustrate where the sulci and fissures are on the spinal cord
….
describe the posterior median SULCUS and anterior median fissures *
divide the posterior/anterior surface of the spinal cord in 2 halves respectively
describe the posterolateral sulcus *
entry point off the posterior (sensory) root
describe the anterolateral fissure *
exit point for the anterior (motor) root
illustrate different pathways through the grey matter in the spinal cord*
….
describe the path of the discriminative touch and perception fibres *
sensory fibres enter the dorsal horns
travel up dorsal column (fasciculus gracilis or fasciculus cuneatus) without synapsing - synapse in the medulla (nucleus gracilis/cuneatus)- cross to the contralateral side
describe the path for pain and temp fibres *
enter the dorsal horn
may travel up/down 1/2 segments in the Lissauer tract (posterolateral fasciculus) then synapse in the dorsal horn in the nucleus proprius
fibres then cross the midline in the anterior commissure and travel in the spinothalamic tract
describe the motor pathways *
a-motor neurons located in anterior horn
exit spinal cord and travel to target
interneurons in anterior horn filter descending motor info and are involved in reflexes
what is the substantia gelatinosa
lamina II of grey matter, first modulation for pain and temp
illustrate the main tracts of the spinal cord
…
describe the spinocerebellar tract *
proprioception (sense of self-movement and body position) from limbs to the cerebellum
describe the lateral corticospinal tract *
motor to ipsilateral anterior motor horn (mostly limb musculature)
main vol movement pathway
85% fibres
describe the spinothalamic tract *
pain and temp from contralateral side
describe the anterior corticospinal tract *
motor to ipsi- and contralateral anterior horn (mostly axial musculature)
innervate trunk
15% fibres
describe the anterior white commissure *
pain and temp fibres cross
anterior corticospinal tract fibres cross
describe the fasciculus gracilis *
sensory - fine touch, proprioception and vibration from ipsilateral lower limb
describe the fasciculus cuneatus *
sensory - fine touch, proprioception and vibration from ipsilateral upper limb
show diagrammatically the corticospinal tract
…
describe the generic neuron pathways of the main sensory pathways *
there are 3 neurons from skin to brain
primary goes into spinal cord (may synapse here or in the medulla)
secondary goes to the thalamus, synapse here for both paths
tertiary goes to the cortex
when the nerves first synapse they cross to thee other side of the body
illustrate the pathway for Discriminative touch, vibration, proprioception *
…
why are reflexes important clinically
they can show the integrity of sensory and motor pathways
and show what’s happening in the brain - the legion get smaller if peripheral nerve legion and bigger if stroke
effect of reflexes
the nerves have many synapses to minimise damage - eg not just lift feet up but enable you to balance
where are the sympathetic preganglionic motoneurons located *
the thoracolumbar region of the cord
in the intermediate horn - this is the site of the motor neurons of the SNS
what are the factors affecting the severity of the spinal legion *
loss of neural tissue - small if trauma, more if metastasis (invade tracts/surgery damage cord) or degenerative disease
vertical level - higher the legion the more disability (more pathways blocked below)
transverse plane - complete/partial section, damage to the white matter is more important than damage to the grey matter because it would affect ascending/descending tracts
how can you treat legions *
either try and repair below the legion
or bypass the legion - bringing neurons from above to below
how does the transverse plane affect severity of spinal legions *
it depends on which tract is affected
if legion at back - sensory pathways affected
anterior - affect muscle of the trunk
lateral - major motor tract for limbs - paralysis
spinothalamic - loss of pain/temp
describe the effect of injury to the lateral corticospinal tract *
stage 1 - spinal shock, inflammation, loss of reflex activity below legion, lasting for days/weeks - flaccid paralysis - cant move but floppy
stage 2 - return of reflexes with graeter vigour - hyperreflexia or spasticity = rigid paralysis - reflex is more excitable - remain after tested
summarise brown-sequard syndrome *
incomplete spinal injury - damage to one side of spinal cord
lose sense of touch, vibrations and/or position in 3D below level of injury - hemiparalysis
sensory loss is strong ipsilaterally - lose pain and temp
what is the function of the cells in the dorsal *horn
sensory cell bodies
what is the function of the cells in the ventral horn *
motor cell bodies.
define nerve *
a bundle of connecting fibres that transmit impulse from the brain to glands/muscles or from the sense organs to the brain and spinal cord
where asre transverse vertebral foramina and what are there functions
transmit vertebral arteries up to brain in cervical vertebrae
action of the sympathetic preganglionic motoneurons *
their axons control visceral function via ventral roots and spinal nerves
what is the lumbar cistern *
the subarachnoid space belwo the end of the spinal cord
