Neurology `
neurology—AnAtomy And Physiology
Neurology `
neurology—AnAtomy And Physiology
SeCTIoN III
470
Spinal tract anatomy
and functions
Remember, ascending tracts synapse and then cross.
trACt And FunCtion
1st-order neuron
synAPse 1
2nd-order neuron
synAPse 2
3rd-order
neuron
Dorsal column
Ascending: pressure,
vibration, fine touch,
and proprioception
Sensory nerve ending
cell body in dorsal root
ganglion enters spinal
cord, ascends ipsilaterally in
dorsal column
Ipsilateral
nucleus
cuneatus
or gracilis
(medulla)
Decussates
in medulla
ascends
contralaterally
in medial
lemniscus
VPL
(thalamus)
Sensory
cortex
Spinothalamic tract
Ascending
Lateral: pain,
temperature
Anterior: crude touch,
pressure
Sensory nerve ending (A
δ
and C fibers) (cell body
in dorsal root ganglion)
enters spinal cord
Ipsilateral gray
matter (spinal
cord)
Decussates at
anterior white
commissure
ascends
contralaterally
VPL
(thalamus)
Sensory
cortex
Lateral corticospinal
tract
Descending: voluntary
movement of
contralateral limbs
UMN: cell body in 1°
motor cortex descends
ipsilaterally (through
internal capsule), most
fibers decussate at caudal
medulla (pyramidal
decussation) descends
contralaterally
Cell body of
anterior horn
(spinal cord)
LMN: leaves
spinal cord
NMJ
Motor neuron signs
sign
umn lesion
lmn lesion
Comments
Weakness
+
+
Lower
MN = everything
lower
ed (less muscle
mass, muscle tone, reflexes, downgoing
toes).
Up
per MN = everything
up
(tone, DTRs, toes).
Fasciculations = muscle twitching.
Positive Babinski is normal in infants.
Atrophy
−
+
Fasciculations
−
+
Reflexes
Tone
Babinski
+
−
Spastic paralysis
+
−
Flaccid paralysis
−
+
Clasp knife spasticity
+
−
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