[UW Anatomy |
Contents]
Function:
Discriminative touch, conscious proprioception, and vibration sense
from the leg, trunk, and arm.
Pathway:
Central processes of dorsal root neurons T7 and below ascend in IPSI.
fasciculus gracilis to reach nucleus gracilis in the caudal medulla.
Processes of dorsal root ganglion cells T6 and above ascend in IPSI.
fasciculus cuneatus and end in nucleus cuneatus. Axons from cells in
nucleus gracilis and cuneatus pass ventrally as internal arcuate
fibers, cross the midline and form the medial lemniscus. Medial
lemniscus ascends to V.P.L. Cells in V.P.L. project to somatosensory
cortex.
Deficits:
Lesion in fasciculus gracilis, nucleus gracilis, fasciculus cuneatus
and nucleus cuneatus results in IPSI. deficits in 2 point
discrimination, vibration sense, and conscious proprioception from
the leg and arm respectively. Lesion in the medial lemniscus results
in CONTRA. deficits.
Other Note:
Lesion in internal arcuate fibers before they cross the midline
results in IPSI. deficits. Lesion of crossing fibers from both
sides=bilateral loss.