SPINAL CORD Flashcards
Somatotopic Organization
segmental organization
Location of SC
from the foramen magnum until L1 (adults) and L3 (newborn)
Subarachnoid Space
lies within this area and extends caudally to the level of S2
Dural Sac
suspends and anchors the spinal cord
Denticulate Ligament
two flattened bands with 21 teeth
Filum Terminale
conus medullaris until the end of the dural sac
Spinal Nerve Roots
strongest fixation and anchorage of the sc to the vertebral canal
Cervical Enlargements
C5-T1 (brachial plexus)
Lumbar Enlargements
L1-S2 (lumbosacral plexus)
Conus Medullaris
terminal end
45 cm in males, 42 cm in females
Spinal Nerves
31 pairs
8 cervical
12 thoracic
5 lumbar
5 sacral
1 coccygeal
motor and sensory fibers
C1 and CO Nerves
no dermatomes (no sensory)
Passageway of C1
atlas and the skull
Passageway of C2
atlas and axis
Exit of Spinal Nerves
intervertebral or spinal foramina
GSA
General Somatic Afferent
input from muscles, bone, skin, and joints
GVA
General Visceral Afferent
input from visceral organs
GSE
General Somatic Efferent
output from ventral horn motor neurons to skeletal muscles
GVE
General Visceral Efferent
output from intermediolateral cell column via prevertebral ganglia to the visceral organs (sympathetic division)
sacral parasympathetic nucleus via intramural ganglia to pelvic viscera
Dorsal Root
enters dorsal lateral sulcus as rootlets
sensory input
joints ventral root to form spinal nerve
Dorsal Root Ganglion
contains pseudounipolar neurons from neural crest origin
sensory input from periphery (GSA and GVA)
Ventral Roots
emerges from ventral lateral sulcus as ventral rootlets
converts motor output from visceral and somatic
Cauda Equina
horsetail
contains lumbosacral plexus (L2-CO)
Dorsal Primary Ramus
skin and muscles of the back
Ventral Primary Ramus
ventral lateral muscles and skin of the trunk, extremities, and visceral organs
Meningeal Ramus
meninges and vertebral column
White communicating rami
myelinated preganglionic and GVA
only found in the thoracolumbar segments (T1-L3)
Gray communicating rami
unmyelinated postganglionic and all spinal nerves
Somite
dermatome, myotome, and sclerotome
Dermatome
cutaneous area
Myotome
muscles
Sclerotome
bones and ligaments
Gray Matter
located centrally
butterfly; H-shaped
central canal
Gray Matter Dorsal Horn
sensory input
rexed laminae (dorsal to ventral)
Rexed Laminae
cytoarchitectural areas
RL I
dorsal marginal nucleus
RL II
substantia gelatinosa
RL III and IV
nucleus proprius; where spinothalamic tract synapses (pressure and vibration)
RL V
neck of RL IV
RL VI
no nociceptive input; sensitive to movement/ stretch of internal joints
RL VII
nucleus dorsalis of Clarke
RL X
central canal
where gray commissure is located
Gray Matter Lateral Horn
viscerosensory input
extends from T1-L3
contains intermediolateral nucleus
T1-T2
cliospinal center of budge (sympathetic innervation of eye)
Gray Matter Ventral Horn
motor function
spinal border cells
sacral parasympathetic nucleus
somatic motor nuclei
spinal accessory nucleus
phrenic nucleus
White Matter
myelinated fibers containing ascending and descending tracts
Dorsal Funiculus
fasciculus gracilis
fasciculus cuneatus
Lateral Funiculus
lateral spinothalamic tract
dorsolateral fasciculus tract of lissauer
spinocerebellar
Ventral Funiculus
vestibulospinal
reticulospinal
anterior spinothalamic tract
Cervical Cord
dorsal intermediate sulci and septa are present
massive ventral horns from C3-C8
Thoracic Cord
h shaped gray matter
dorsal
Lumbar Cord
massive ventral horns (L3-5)
butterfly shaped
Myotatic Reflex
monosynaptic and ipsilateral muscle stretch
afferent and efferent limb
reciprocal inhibition: contraction of agonist and relaxation of antagonist
Afferent Limb
muscle spindle, DRG neuron, and type Ia fiber
Efferent Limb
ventral horn motor neuron
Four commonly tested muscle stretch reflexes
ankle jerk: S1
knee jerk: L2-L4
biceps: C5-C6
triceps: C7-C8
Ascending Spinal Tracts
sensory information
first order neuron will always be DRG
usually decussates before reaching final destination
DCML Tract (Dorsal Column Medial Lemniscus)
tactile, discrimination, vibration, recognition, and joint muscle sensation
mediates conscious proprioception
receives input from pacini’s, meissner’s corpuscles, joint receptors, muscle spindles, golgi tendon organs
DCML Pathway
1st order: DRG (fasciculus gracilis from LE; fasciculus cuneatus from UE)
2nd order: medulla (internal arcuate fibers decussate to form the medial lemniscus that ascends thru the contralateral brainstem)
3rd order: VPL of thalamus (somatosensory cortex; 3,1,2)
Ventral Spinothalamic Tract
light pressure and touch
slow pain
free nerve endings and merkel’s tactile discs
Anterior Spinothalamic Tract
pain and temperature
fast pain
a delta and c fibers
sacral fibers: dorsolaterally
cervical fibers: ventromedially
Ventral Spinothalamic Tract Pathway
1st order: DRG
2nd order: substantia gelatinosa
3rd order: VPL of thalamus
Lateral Spinothalamic Tract Pathway
1st order: Dorsolateral tract of Lissauer
2nd order: substantia gelatinosa
3rd order: VPL of thalamus
Dorsal Spinocerebellar Tract
unconscious proprioceptive information
fine coordination of posture and movement of individual muscles of LE
muscle spindles, GTO, and pressure receptors
uncrossed tract: goes straight to cerebellum and does not decussate
Lateral Spinocerebellar Tract
unconscious proprioceptive information
coordinated movement and posture of the entire lower extremity
crossed tract
Dorsal Spinocerebellar Tract Pathway
1st order: DRG (C8-S3)
-afferent limb for muscle stretch reflexes, medial root entry zone
2nd order: Nucleus Dorsalis of Clarke
-ascend in lateral funiculus
-inferior peduncle –> rostral and ventral cerebellar vermis
-terminate ipsilaterally as mossy fibers
Lateral Spinocerebellar Tract Pathway
1st order: DRG (L1-S2); muscle stretch reflexes
2nd order: Spinal Border Cells in Ventral Horns
-decussate in the ventral white commissure
-ascend in lateral funiculus
-superior peduncle
-terminate contralaterally as mossy fibers of rostral cerebellar vermis
Cuneocerebellar Tract
UE equivalent of dorsal spinocerebellar tract
Cuneocerebellar Pathway
1st order: DRG (C2-T7)
-project axons via fasciculus cuneatus to caudate medulla
2nd order: accessory cuneate nucleus of medulla
-synapse via inferior cerebellar
-terminates ipsilaterally of anterior lobe of cerebellum
Descending Spinal Tracts
somatic and visceral motor
originates in the cerebral cortex
Lateral Corticospinal (Pyramidal) Tract
volitional skilled motor activity
input from paracentral lobule (contralateral leg and foot)
supplied by ACA
Lateral Corticospinal (Pyramidal) Tract Origin and Transmission
- premotor cortex (BA 6)
-motor cortex (BA 4)
-postcentral sensory cortex (3,1,2)
terminates via interneurons (modulates preciseness)
Lateral Corticospinal (Pyramidal) Tract Fibers
90% between 1-4 micra
>20 micra= Giant Cells of Betz (found in precentral gyrus and anterior paracentral lobule)
Lateral Corticospinal (Pyramidal) Pathway
- posterior limb of internal capsule
- middle 3/5 of crus cerebri of midbrain
- bases of pons
- pyramid of medulla (pyramidal decussation/ great motor decussation)
- medial lemniscus: great sensory decussation
Transection of Lateral Corticospinal Pathway
Babinski’s sign
Ventral Corticospinal Tract
small uncrossed tract
decussates in ventral white commissures
controls axial muscles
Vestibulospinal Tract
arises in the ipsilateral lateral vestibular nucleus, giant cells of Dieters
controls extensor tone
located in ventral funiculus
uncrossed tract
concerned with postural activity and associated with balance
Rubrospinal Tract
arises in the contralateral red nucleus in the midbrain
controls flexor tone
ventral to the lateral corticospinal tract
Descending Autonomic Tracts
sympathetic - T1-L3
parasympathetic - S2-4
ciliospinal center/ center of budge -T1-T2
Horner’s Syndrome
damage to ciliospinal center
